Precast Concrete Barriers

MOT / UBC

Testing of Bridge Barrier Anchorages

Developing and Testing of Precast Concrete Bridge Barrier Anchorages to meet the Requirements for PL-2 Barrier Systems of the Canadian Highway Bridge Design Code at

University of British Columbia, UBC Prepared by K. Bleitgen Edited by S. F. Stiemer

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Conceptual Conceptual formu lation The objectives of the research and testing will be as follows: Research and testing of the precast concrete bridge barriers shall result in developing and testing anchorages that meet the requirements for PL2 barrier systems as given by the Canadian Highway Bridge Design Code (CHBDC). The scope of the research and testing for the precast concrete bridge barriers will include the following: 1. Review Canadian Highway Bridge Design Code (CHBDC) requirements for bridge barriers 2. Literature review of background to CHBDC requirements of bridge barriers and other background regarding bridge barriers and bridge testing 3. Review the effect of having inter-connection between adjacent precast concrete barriers 4. Compare British Columbia Ministry of Transportation (BC MoT) anchorage details for precast concrete bridge barriers to details by other jurisdictions / suppliers suppliers 5. Review the effect of type of bridge on the anchorage capacity: - Barrier anchored to concrete slab - Barrier anchored to box girder flange 6. Carry out site visits to existing bridges to see the existing BC MoT precast concrete bolt down barrier system in service 7. Carry out visits to the fabrication plants where the precast concrete barriers are fabricated and liaise with the fabricators regarding fabrication issues

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Ab A b s t r act ac t In this report, an introduction into precast concrete bridge barriers which are used in the Province of British Columbia in Canada is given with an emphasis on bolt-down barriers. Concrete barriers appear to be simple and uncomplicated, but in reality, they are sophisticated safety devices. Barriers are developed to delineate the superstructures edge to reduce the consequences of vehicles leaving the roadway or humans leaving the sidewalk. The shape of a barrier as well as the type of anchorage are the most important features in the design of a barrier. The design can be done either with a crash test or an analysis method, i.e. the yield line analysis and strength design method or finite element analysis. Due to constantly updated design provisions established in Codes in order to improve the performance of barriers, considerable amounts of research and development of new design methods have been carried out. The basics of the design requirements of barriers have changed dramatically in the last twenty years. Since most nowadays used precast concrete bridge barriers are developed based on the 1988 Code, the need of an up-to-date design became necessary. Therefore, the Ministry of Transportation of British Columbia started a series of research projects to satisfy that need. This report is the first research report which will be followed soon by further projects and gives an introduction into bolt-down precast concrete bridge barriers. It gives an overview on applicable Codes, their precursor as well as relevant literature of other jurisdictions. Finally the most common barriers and their superstructures as well as comparable ones from other jurisdictions are presented.

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List of Contents Conceptual formulation Abstract List of Contents List of Tables List of Figures 1. Introduction 2. The hierarchy and application area of applicable Codes 2.1 In Canada 2.2 In the United States of America 3. Review of the Canadian Highway Bridge Design Code (CHBDC) requirements for bridge barriers 3.1 Traffic barrier 3.1.1 Performance Level 3.1.2 Crash test requirements 3.1.3 Anchorages 3.2 Pedestrian barrier 3.3 Bicycle barrier 3.4 Combination barrier 4. Literature review of background to CHBDC requirements of bridge barriers and other background regarding bridge barriers and barrier testing 4.1 The precursor of the Canadian Highway Bridge Design Code 4.1.1 Review of CAN/CSA-S6-88 requirements of bridge barriers 4.1.2 Comments on changes between CAN/CSA-S6-88 and CAN/CSA-S6-00 4.1.3 Review of OHBDC-91-01 requirements of bridge barriers 4.1.4 Comments on changes between OHBDC-91-01 and CAN/CSA-S6-00 4.1.5 General comment on the changes of the CHBDC to the precursor 4.2 Other background literature regarding the CHBDC 4.2.1 AASHTO LRFD Bridge Design Specifications, Section 13, Railings, from 1997 4.2.2 AASHTO LRFD Bridge Design Specifications, Section 13, Railings, 2004: nd rd Important changes from the 2 to the 3 Edition 4.2.3 Appendix A of AASHTO LRFD Bridge Design Specifications, 1997 4.2.4 Appendix A of AASHTO LRFD Bridge Design Specifications, 2004: Important nd rd changes from the 2 to the 3 Edition 4.2.5 NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features 4.3 Other literature regarding bridge barriers and barrier testing 4.3.1 Basics of Concrete Barriers 4.3.2 Review of the Washington State Bridge Design Manual 4.3.3 Comment on the Washington State Bridge Design Manual 5. Literature review of BC MoT's design literature regarding requirements of precast concrete bridge barriers 6. Review the effect of having inter-connection between adjacent precast concrete barriers 6.1 The hook and eye connection

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ii iii iv v vi 1 3 3 3 5 5 6 7 8 9 10 11 12 12 12 13 13 15 16 16 17 19 21 29 29 30 30 31 34 35 37 37

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6.2 The pin and loop connection 39 6.3 The inter-connection effect between adjacent precast barriers 41 7. Compare British Columbia Ministry of Transportation (BC MoT) anchorage details for precast concrete bridge barriers to details by other jurisdictions 42 7.1 Anchor details of the MoT of British Columbia 42 7.1.1 The 810 mm high precast concrete bridge parapet 42 7.1.2 The 865 mm high precast concrete bridge parapet 45 7.1.3 The 875 mm high precast concrete bridge parapet 47 7.2 Anchorage details of precast concrete bridge barriers of other Canadian Provinces and Territories than British Columbia 50 7.2.1 Anchorage details McKenzie Creek – Hwy 6, used by the Ministry of Transportation Ontario (MTO) 1991 50 7.3 United States of America anchorage details 54 7.4 Comparison of the anchorage details 57 7.4.1 Comparison of the BC MoT bolt-down precast concrete bridge barriers with the McKenzie precast bridge barrier 58 7.4.2 Comparison of the BC MoT bolt-down precast concrete bridge barriers with the L.B. Foster NJ-Shape precast bridge railing 58 8. Review the effect of type of bridge (concrete slab vs. box girder) on the anchorage capacity 60 8.1 The anchor capacity of barriers anchored to concrete slabs 62 8.1.1 The Misinchinka Bridge, # 6819 62 8.1.2 The Hudgens Bridge, # 7476 64 8.1.3 The Twan Creek Bridge, # 8023 66 8.2 The anchor capacity of barriers anchored to box girder flange 67 8.2.1 The Standard Precast Concrete Bridge, # 2965 67 8.2.2 The Elkins Bridge Precast Concrete Parapets, #7780 69 9. Carry out site visits to existing bridges to see the existing BC MoT precast concrete bolt down barrier system in service 71 9.1 Detailed information of the construction of the Birkenhead Causeway Bridge No. 8024 71 9.2 Site visit: Birkenhead Causeway Bridge No. 8024 73 10. Precast concrete barrier fabrication plants in British Columbia 76 Conclusions 80 References 81 Appendix 83

Lis t of Tables Table 1 – Traffic barrier loads, from Figure 3 .8.8.1, CAN/CSA-S6-00 .......................................... 9 Table 2 – Bridge railing Performance Levels and crash test criteria from Table 13.7.2.1, AASHTO LRFD Bridge Design Specifications, 1997 .............................................. 18 Table 3 – Bridge railing Testing Levels and crash test criteria, from Figure 13.7.2-1, AASHTO LRFD Bridge Design Specifications 2004................................................................. 20 Table 4 – Design forces for traffic railings, from Table A13. 2-1, AASHTO LRFD Bridge Design Specifications, 2004 ................................................................................................... 29 Table 5 – Vehicle impact loading on traffic barrier by WSDOT, WSBDM, Section 10.2.4, Design Criteria ........................................................................................................... 33


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Table 6 – List of precast concrete bridge barriers from Section 941, Standard Specifications for Highway Construction, BC MoT ............................................................................... 36 Table 7 – Standard precast concrete bolt-down systems used by the BC MoT............................ 60 Table 8 – Precast concrete bolt-down system used by the MoT Ontario ..................................... 60 Table 9 – Precast concrete bolt-down systems used by the US. DoT, FHWA............................. 60 Table 10 – List of fabricators of precast concrete bridge barriers within British Columbia ........ 76

List of Figur es Figure 1 – Sketch of the hierarchy of the Codes concerning traffic barriers in the USA............... 4 Figure 2 – Application of traffic design load s to traffic barriers, from Figure 12.5.2.4, CAN/CSAS6-00 ................................................. ........................................................................... 9 Figure 3 – The application of pedestrian and bicycle design loads to barriers, from Figure 12.5.3.2, CAN/CSA-S6-00 .......................................................................................... 10 Figure 4 – Application of pedestrian loads for pedestrian railings, from Figure 5-4.5.2.3, OHBDC-91-01 ........................................................................................................... 14 Figure 5 – Application of pedestrian loads for bicycle railings and combination barriers, from Figure 5-4.5.2.3, OHBDC-91-01................................................................................ 15 Figure 6 – Pedestrian railing loads, from Figure 13.8.2.1, AASHTO LRFD Bridge Design Specifications ............................................................................................................. 18 Figure 7 – Bicycle Railing Loads, from Figure 13.9.3.1, AASHTO LRFD Bridge Design Specifications ............................................................................................................. 19 Figure 8 – Geometrical definitions of two typical traffic railings, from Figure A13.1.1-1, AASHTO LRFD Bridge Design Specifications .................................................. ...... 21 Figure 9 – Post setback criteria, from Figure A13.1.1-3, AASHTO LRFD Bridge Design Specifications ............................................................................................................. 22 Figure 10 – Nomenclature for traffic railing equations, from Figure CA13.2.1, AASHTO LRFD Bridge Design Specifications, 1997 .............................................. ............................. 23 Figure 11 – Design forces for traffic railings, from Table A13. 2-1, AASHTO LRFD Bridge Design Specifications, 1997 ................................................ ....................................... 24 Figure 12 – Railing design forces, from Figure A13.2-1, AASHTO LRFD Bridge Design Specifications ............................................................................................................. 24 Figure 13 – Yield Line Analysis of concrete parapet walls for impact within wall segment an d near end of wall segment, part 1 of Table A13.3.1-1/2, AASHTO LRFD Bridge Design Specifications................................................................................................. 25 Figure 14 – Yield Line Analysis of concrete parapet walls for impact within wall segment, p art 2 of Table A13.3.1-1, AASHTO LRFD Bridge Design Specifications........................ 26 Figure 15 – Possible failure modes for post-and-beam railings, from Table A13.3.2-1, AASHTO LRFD Bridge Design Specifications........................... ............................................... 26 Figure 16 – Combination concrete wall and metal rail evaluation-impact at (1) mid-span of rail and (2) at a post, from Table A13.3.3-1/ 2, AASHTO LRFD Bridge Design Specifications ............................................................................................................. 28 Figure 17 – Detail drawing of the F-shape and Single Slope barrier, WSDoT, Figure 10.2.3-2 . 32 Figure 18 – Hooks and eyes, from Standard Specifications for Highway Construction 2006, SP941-04.01.01 .......................................................................................................... 37 Figure 19 – Eye of the BC MoT's precast concrete bridge barrier, from drawing 7780-5 ........... 38


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Figure 20 – Hook and eye end section of a barrier in 3D, standard median barrier 810 mm, from drawing SP941-02.01.08 and 09, BC MoT................................................ ................ 38 Figure 21 – Plan view on the end of a hook and eye unit, standard median barrier 810 mm, from drawing SP941-02.01.03 and 04, BC MoT................................................ ................ 38 Figure 22 – Connection detail (plan view) of the hook (left) and eye (right) system, standard median barrier 810 mm, drawing SP941-02.01.03, BC MoT .................................... 39 Figure 23 – Plan view of the pin and loop system, from drawing C-8d, Standard Drawings, WSDoT ...................................................................................................................... 39 Figure 24 – The pin in detail, from drawing C-8d, Standard Drawings, WSDoT........................ 40 Figure 25 – Top and side view of the whole barrier, showing the anchors for the pin and loop system, from drawing C-8d, Standard Drawings, WSDoT........................................ 40 Figure 26 – View on the end of the barrier, from drawing C-8d, Standard Drawings, WSDoT.. 41 Figure 27 – 810 mm high precast concrete bridge barrier, from drawing 8023-22, BC MoT ..... 42 Figure 28 – Typical section through the 810 mm high precast concrete bridge barrier, from drawing 8023-22, BC MoT .................................................. ...................................... 43 Figure 29 – Bolt sleeve detail of the 810 mm high precast concrete bridge barrier, from drawing 8023-22, BC MoT ............................................... ....................................................... 44 Figure 30 – Bolt detail of the 810 mm high precast concrete bridge barrier, from drawing 802322, BC MoT ............................................................................................................... 44 Figure 31 – 865 mm high precast concrete bridge barrier, from drawing 8023-22, BC MoT ..... 45 Figure 32 – Typical section through the 865 mm precast parapet, from drawing 2965-4, BC MoT45 Figure 33 – Blockout and bolt sleeve detail of the 865 mm high barrier, from drawing 2965-4, BC MoT ................................................... .................................................................. 46 Figure 34 – Bolt sleeve detail of the 865 mm high barrier, from drawing 2965-4, BC MoT....... 46 Figure 35 – One possible anchor bolt of the 865 mm high precast concrete bridge parapet, from drawing 2965-23, BC MoT .................................................. ...................................... 47 Figure 36 – 875 mm high precast concrete bridge barrier, from drawing 8023-22, BC MoT ..... 47 Figure 37 – Typical section through the 875 mm high precast concrete bridge barrier, from drawing 7476-12, BC MoT .................................................. ...................................... 48 Figure 38 – Bolt sleeve detail of the 875 mm high precast concrete bridge barrier, from drawing 7476-12, BC MoT ............................................... ....................................................... 49 Figure 39 – Blockout and bolt sleeve detail of the 875 mm high barrier, from drawing 7476-12, BC MoT ................................................... .................................................................. 49 Figure 40 – Cut through barrier, anchor type 1, used by the Ministry of Transportation, Ontario51 Figure 41 – Cut through barrier, anchor type 2, used by the Ministry of Transportation, Ontario51 Figure 42 – Anchor details: type 1 and type 2, used by the Ministry of Transportation, Ontario 52 Figure 43 – Step I to III of the construction sequence of the McKenzie Creek Barrier, used by the Ministry of Transportation, Ontario .............................................. ............................. 53 Figure 44 – Step IV and VII of the construction sequence of the McKenzie Creek Barrier, used by the Ministry of Transportation, Ontario ............................................ .................... 54 Figure 45 – Section through L.B. Foster NJ-Shape barrier, from Bridge Rail Guide 2005, FHWA55 Figure 46 – Bolt detail of the L.B. Foster NJ-Shape barrier, from Bridge Rail Guide 2005, FHWA ........................................................................................................................ 56 Figure 47 – Barrier end detail of the L.B. Foster NJ-Shape barrier, from Bridge Rail Guide 2005, FHWA ........................................................................................................................ 57


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Figure 48 – Failure modes for anchors under tension and shear load, from CSA A23.3-04, Figure D.1 and D.2 ................................................................................................................ 61 Figure 49 – Plan and elevation view of the Misinchinka Bridge, from drawing 6819-9, BC MoT62 Figure 50 – Parapet anchor insert of the Misinchinka Bridge, from drawing 6819-8, BC MoT.. 63 Figure 51 – Misinchinka Bridge after the installation of the anchor bolt, from drawing 6819-10, BC MoT ................................................... .................................................................. 63 Figure 52 – Plan and elevation view of the Hudgens bridge, from drawing 7476-12, BC MoT.. 65 Figure 53 – Section through exterior bridge deck, from drawing 7476-12, BC MoT.................. 65 Figure 54 – Detail drawing of the nut in the panel deck, from drawing 7476-12, BC MoT ........ 65 Figure 55 – The Hudgens precast concrete bridge barrier # 7476 after the installation of the anchor bolt, from drawing 7476-12, BC MoT ................................................... ........ 66 Figure 56 – Detail of the precast concrete deck bridge, from drawing 8023-21, BC MoT.......... 66 Figure 57 – Parapet connection to deck at Twin Creek bridge, from drawing 8023-22, BC MoT67 Figure 58 – Plan and elevation view of the standard precast parapet MK P1, from drawing 29654, BC MoT ............................................... .................................................................. 68 Figure 59 – Section through exterior stringer MK 700/16/E, from drawing 2965-23, BC MoT . 68 Figure 60 – Standard precast concrete bridge after installation of the anchor bolt, from dwg. 2965-6, BC MoT ................................................. ....................................................... 69 Figure 61 – Elkins bridge after the installation of the anchor bolt, from drawing 7780 -6, BC MoT70 Figure 62 – Section through the Birkenhead Causeway Bridge barrier, from dwg. 8024-9, BC MoT............................................................................................................................ 71 Figure 63 – Plan and elevation view of the Birkenhead Causeway Bridge barrier, from dwg. 8024-9, BC MoT ................................................. ....................................................... 72 Figure 64 – Cut through box stringer of the Birkenhead Causeway Bridge, from dwg. 8024-9, BC MoT ................................................... .................................................................. 72 Figure 65 – After placing the Birkenhead Causeway Bridge barrier, from dwg. 8024-9, BC MoT73 Figure 66 – Filled precast concrete barrier forms at the plant of Eagle West Truck & Crane ..... 77 Figure 67 – Hook bars used for the connection of adjacent barriers at the plant of Eagle West Truck & Crane................................... ......................................................................... 77 Figure 68 – Eye bar(s) used for the connection of adjacent barriers at the plant of Eagle West Truck & Crane................................... ......................................................................... 78 Figure 69 – Precast concrete barriers after 3 days at the plant of Eagle West Truck & Crane .... 78 Figure 70 – Side and end view of a precast concrete bridge barrier at the plant of Eagle West Truck & Crane................................... ......................................................................... 79 Figure 71 – Side and end view of the precast concrete bridge barrier anchor at Eagle West Truck & Crane ................................................ ...................................................................... 79


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1.


Introduction

The objective of this report is to give an introduction into precast concrete reinforced bridge barriers and in particular into bolt-down precast barriers used in British Columbia in Canada. Barrier design provisions established in codes are constantly updated in order to improve the performance of barriers to help to restrain errant vehicles from leaving the roadway or humans from leaving the sidewalk. Considerable amounts of research and development of new structural systems is being carried out. However, there are still many barrier design requirements that remain challenging. The 2000 edition of the Canadian Highway Bridge Design Code (CHBDC), as well as the third edition of the American Association of State Highway and Transportation Officials (AASHTO), Load and Resistance Factor Design (LRFD), Barrier Design Specifications and National Cooperative Highway Research Program (NCHRP), Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features, contain significant changes compared to previous editions regarding barrier design requirements. The main feature of these standards is the requirement for crash-testing in order to establish a specified level to which a traffic barrier will perform (Performance Level, Testing Level). Due to the fact that many Codes and Guidelines which deal with barriers are conflicted between the each other, the second chapter gives a short introduction into relevant Codes showing their hierarchy and application area. In the third chapter, a summary of the section that deals with barriers in the Canadian Highway Bridge Design Code (CHBDC) is presented. Many of the nowadays used precast concrete bridge barriers are designed before 2000, based on the Canadian Highway Bridge Design Code (CHBDC) from 1988. Due to this high importance, the precursor of the Canadian Highway Bridge Design Code (CHBDC) published in 2000 as well as their background, are introduced in Chapter 4.1. Afterwards a general introduction into concrete barriers is given. It explains the reason for the shape of a barrier and gives some historical background concerning the development of barriers (Chapter 4.2). Then, the main related literatures to the Canadian Highway Bridge Design Code (CHBDC) as the AASHTO LRFD Bridge Design Specifications and the NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features are presented. To make a comparison of the applicable Codes regarding barriers used in British Columbia, the state Washington in the United States is chosen due to similar conditions. Therefore a summary of the Washington State Bridge Design Manual as well as a comment on the differences is given. Then, in Chapter 5, the design and production requirements of precast concrete barriers in British Columbia which are given by the Ministry of Transportation of BC are explained. These design provisions give all necessary information for the production of barriers and are therefore relevant for fabrication plants. One visit to a fabrication plant wa s done and is presented in Chapter 10.


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Since precast concrete reinforced barriers have to be delivered to the bridge site, they can only be produced in small pieces. Thus, the connection between two adjacent barriers produces an interconnection effect which can influence the design and is therefore analysed in Chapter 6. The main purpose of the research series is to get a proof for used precast concrete bridge barrier how they perform and in which level (Performance Level or Testing Level) they can be categorized. Therefore, the three main precast concrete bridge barriers which are used in British Columbia are analysed in the beginning of Chapter 7. Since crash tests are really expensive and time intensive, the Ministry of Transportation wants to design the barriers either with showing there are similar to proofed barriers and thus crashworthy or with analysis methods. Due to that comparable precast concrete bridge barriers of other jurisdictions are presented. Finally, a comparison between the barriers used in British Columbia and the barriers of other jurisdictions is done. The Ministry of Transportation of British Columbia uses the aforementioned three barrier types in combination with different superstructures which results in five different models. Precast concrete bridge barriers are combined either with a twin box stringer or a concrete panel deck superstructure. Since different bolt systems are used for different superstructure types, anchorage capacities are determined when the necessary information was present. Finally, in Chapter 9, the results of a site visit to an existing bridge which is built with the boltdown precast concrete bridge barriers are presented after the bridge itself is explained.


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2.


The hierarch y and applic ation area of applic able Codes

This short introduction is supposed to give an overview of existing Codes and explains the hierarchy of the Codes as well as its area of application. Since the first part of this research report consists of a literature review of existing Codes dealing with traffic barriers this overview of applicable Codes should help to understand the coherences between the different Codes and its countries. It is important to understand the Code's hierarchy and its appropriate application because there occur conflicts between the structural design literatures. In general the national code provides a general design method whereas the state code deals with specifications.

2.1

In Canada

In Canada the National Code which deals with bridge barriers is the Canadian Highway Bridge Design Code published by the Canadian Standards Association (CSA) for highway bridge design. As a subdivision, each state of Canada is having additional specifications and standards establishing detailed requirements, consistent with current nationwide practices, which apply to common highway bridges. For example in British Columbia, the British Columbia Ministry of Transportation (BC MoT) published the Standard Specifications for Highway Construction 2006 as well as the Design Standards, Bridge Standards and Procedures, which have to be applied in British Columbia. But nevertheless the system is not as clear as it seems, because some Codes give references to relevant literature of other jurisdictions. For example, concerning crash test requirements, the Canadian Highway Bridge Design Code refers to the American Association of State Highway and Transportation Officials (AASHTO), Guide Specifications of Bridge Railings. And in addition, the AASHTO Guide Specifications of Bridge Railings refers further to the National Cooperative Highway Research Program (NCHRP), Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features.

2.2

In the United States of America

Since most comparisons are done with the United States of America, the hierarchy and the application areas of the Codes of the United States of America concerning bridge barriers are explained as well. The American Association of State Highway and Transportation Officials (AASHTO) Load and Resistant Factor Design (LRFD) Bridge Design Specifications is intended to serve as the National Standard for use in the development of the Department's own structural specifications. Since the United States of America are quite big and consists of many states, the next lower level consists of three subdivisions which are (1) the Western Federal Lands Highway Division, (2) the Central Federal Lands Highway Division, and (3) the Eastern Federal Lands Highway Division. Each division has a different Project Development and Design Manual. precast concrete barriers in British Columbia.doc

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The next level under these three subdivisions are the states itself. A sketch of the hierarchy of the Codes in the United States of America is given in the beneath figure.

Y R T N U O C A S U

N L O I A S I R V E I D D E B F U S

L E V E L E T A T S

AASHTO LRFD Bridge Design Specifications

Western Federal

Central Federal

Eastern Federal

Lands Highway

Lands Highway

Lands Highway

Division (WFLHD)

Division (CFLHD)

Division (EFLHD)

Alaska

California

Maryland

Washington

Nevada

Kentucky

Oregon

Utah

Virginia

Idaho

Arizona

Mississippi

Montana

Wyoming

Tennessee

Wyoming

Colorado

Virginia

...

...

Figure 1 – Sketch of the hierarchy of the C odes concerning traffic barriers in the United States of America


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3. Review of the Canadian Highway Bri dge Design Code (CHBDC) requirements for bri dge barri ers The Canadian Highway Bridge Design Code CAN/CSA-S6-00 is prepared by the Canadian Standards Association (CSA) for highway bridge design in Canada and was published in December 2000. The requirements for the design of barriers are specified in section 12. Barriers on bridges receiving salt are exposed to a highly corrosive environment. To ensure long-term performance, these barriers must either be made from materials that can withstand this environment or be protected by an adequate protective coating. The barriers are divided into four different types of barriers according to their function:

• • • •

Traffic barrier; Pedestrian barrier; Bicycle barrier; and Combination barrier.

In the appraisal of a barrier the specific regulations, which will be mentioned in the following subsections, are not the only factors to consider. There also exist some general factors which should not be underestimated. These factors are durability, ease of repair, snow accumulation on and snow removal from deck, visibility through or over barrier, deck drainage, future wearing surfaces, and aesthetics. Damaged barriers need to be repaired quickly with minimal disruption to traffic. Traffic barriers should be designed with features such as anchorages that are unlikely to be damaged or cause damage to the bridge deck during an accident and modular construction using prefabricated sections that allow damaged sections to be repaired quickly.

3.1 Traffic barr ier Traffic barriers should be provided on both sides of highway bridges to delineate the superstructure edge and therefore to reduce the consequences of vehicles leaving the roadway upon the occurrence of an accident. Crash tests are used to determine barrier adequacy in reducing the consequences of vehicles leaving the roadway. If a barrier has the same details as those of an existing traffic barrier the adequacy can be determined from an evaluation of the existing barrier's performance when struck by vehicles. The adequacy of a traffic barrier in reducing the consequences of a vehicle leaving the roadway is based on the level of protection provided to the occupants of the vehicle, to other vehicles on the roadway and to people and property beneath the bridge. This protection is provided by retaining the vehicle and its cargo on the bridge, by smoothly redirecting the vehicle away from the barrier and by limiting the rebound of the vehicle back into traffic.


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3.1.1 Performanc e Level Traffic barrier requirements vary from bridge site to bridge site and are based on the expected frequency and consequences of vehicle accidents at a bridge site. This procedure assumes that the frequencies and consequences of vehicle accidents at bridge sites are a function of many variables. The ranking system, used in CAN/CSA S6-00 to determine the site conditions of a bridge site, are named Performance Level (PL) and are defined as the following (CAN/CSA-S600, Section 12.2 Definitions):

•

Performance Level 1 (PL-1): The performance level for traffic barriers on bridges where the expected frequency and consequences of vehicles leaving the roadway are similar to that expected on low traffic volume roads. Crash test requirements require crash testing with a small automobile and a pickup truck in accordance with the AASHTO (American Association of State Highway and Transportation Officials) Guide Specifications for Bridge Railings.

•

Performance Level 2 (PL-2): The performance level for traffic barriers on bridges where the expected frequency and consequences of vehicles leaving the roadway are similar to that expected on high to moderate traffic volume highways. Crash test requirements require crash testing with a small automobile, a pickup truck, and a single unit truck in accordance with the AASHTO Guide Specifications for Bridge Railings.

•

Performance Level 3 (PL-3): The performance level for traffic barriers on bridges where the expected frequency and consequences of vehicles leaving the roadway are similar to that expected on high traffic volume highways with high percentage of trucks. Crash test requirements require crash testing with a small automobile, a pickup truck, and a tractortrailer truck in accordance with the AASHTO Guide Specifications for Bridge Railings.

Alternative Performance Levels, as mentioned in Section 12.5.2.1.1 in CAN/CSA-S6-00, have to be approved by the Regularity Authority for the bridge and defined by specifying their crash test requirements. These levels shall be considered along with Performance Level 1, 2, or 3 when determining the optimum performance level which is the one with the least costs. The optimal level of traffic barrier performance at a bridge site is assumed to be the level giving the least costs where costs includes the costs of supplying and maintaining a traffic barrier as well as the costs of the accidents expected with the use of the traffic barrier. The assumed accident rates, accident severities and traffic barrier costs used by a computer-based Benefit-Cost Analysis Program (BCAP) in determine optimal levels of traffic barrier performance as well as the engineering judgement used to adjust these optimal levels for use in the Codes are given in AASHTO (1989). The Performance Levels are determined with the barrier exposure index (Be) which is based on the estimated average annual daily traffic for the first year after construction (AADT1). Other influencing parameters, as the type of the highway, the curvature of the highway, the grade of the highway and the height of the superstructure as well as the type of substructure, are considered in the barrier exposure index.


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The barrier exposure index is defined as:

Be =

(AADT1 ) K h K c K g Ks 1000

Where: AADT1 ≤ 10,000 vehicles per day per traffic lane per vehicle speeds 80km/h or greater K h

= highway type factor, see CAN/CSA-S6-00, Table 12.5.2.1.2 (a)

K c

= highway curvature factor, see CAN/CSA-S6-00, Table 12.5.2.1.2 (b)

K g

= highway grade factor, see CAN/CSA-S6-00, Table 12.5.2.1.2 (c)

K s

= superstructure height factor, see CAN/CSA-S6-00, Table 12.5.2.1.2 (d)

With the design speed and the percentage of trucks as well as the barrier exposure index the Performance Level can be determined with tables given under CAN/CSA-S6-00 Section 12.5.2.1.3. There exist three different tables for three different barrier clearances in the Canadian Highway bridge design Code:

•

Table 12.5.2.1.3 (a) for Barrier Clearance ≤ 2.25m

•

Table 12.5.2.1.3 (b) for 2.25m < Barrier Clearance ≤ 3.75m

•

Table 12.5.2.1.3 (c) for Barrier Clearance > 3.75m

Due to the Performance Level a minimum barrier height can be determined with Table 12.5.2.2 from CAN/CSA-S6-00. The minimum barrier heights for PL 1, 2, and 3 traffic barriers are 0.68 m, 0.80 m, and 1.05 m respectively. Traffic barrier height requirements are intended to prevent impacting vehicles from vaulting or rolling over a barrier. The higher the center of gravity of the impacting vehicle, the greater the required traffic barrier height needed to contain it. And the geometry of the roadway face of a traffic barrier as well as the transition into the roadway face of the approach roadway traffic barrier shall have a smooth and continuous alignment, as laid out in Section 12.5.2.2 in CAN/CSA-S6-00. Where a traffic barrier is located between the roadway and a sidewalk or bikeway, the sidewalk or bikeway face of the barrier should have a minimum height of 0.60 m measured from the surface of the sidewalk or bikeway.

3.1.2 Crash test requirements With the defined Performance Level the crash test requirements which should be in accordance with the crash test requirements of AASHTO Guide Specifications for Bridge Railings are defined, as mentioned in Section 12.5.2.3 in CAN/CSA-S6-00. Those crash test requirements shall be satisfied along the entire length of a traffic barrier, including at any changes in barrier type, shape, alignment, or strength that may affect the barrier performance. Alternative Performance Levels shall meet the crash test requirements of the optimum Performance Level or of a more severe Performance Level as considered.


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Under Section 12.5.2.3.2 CAN/CSA-S6-00, the crash test requirements for traffic barrier transitions are defined. They should meet the crash test requirements used for appraising the approach roadway traffic barrier, provided that it has been crash tested to requirements that test its geometry, strength, and behaviour to an equivalent or more severe level. These requirements are normally in accordance with Test Designation 30 of NCHRP NCHRP 230: Recommended Procedures Procedu res for the Safety Performance Performanc e Evaluation of Highway Appurtenances (Michie 1981) which requires crash testing with a 2040 kg automobile travelling 96 km/h and striking the transition at an impact angle pf 25°. The crash test requirements for longitudinal barrier Test Levels 2, 4, and 5 of National Cooperative Highway Research Program (NCHRP) Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features shall be taken as meeting the crash test requirements for Performance Level 1, 2, and 3 respectively. According to Section 12.5.2.3.4 in CAN/CSA-S6-00, any changes in details effecting the geometry, strength, or behaviour of the traffic barrier or traffic barrier transition that meets the aforementioned requirements can be demonstrated to not adversely affect barrier-vehicle interaction.

3.1.3 Anchorages The performance of the traffic barrier anchorage during crash testing is the basis for its capability. In case no significant damage occurs in the anchorage or deck during crash testing, the anchorage is considered to be acceptable. If there are no crash testing results for the anchorage available, the anchorage and deck shall be designed to resist the maximum bending, shear and punching loads that can be transmitted to them by the traffic barrier. The loads should shou ld be applied as the following:


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Figure 2 – Application of traffic design loads to traffic barriers, from Figure 12.5.2.4,

CAN/CSA-S6-00

But the loads have to be greater than those resulting from the loads defined in Section 3.8.8, Barrier Loads, in CAN/CSA-S6-00. The transverse, longitudinal, and vertical loads should be applied simultaneously and are specified as the following:

Table 1 – Traffic barrier loads, from Figure 3.8.8.1,

CAN/CSA-S6-00

3.2 3.2 Pedestr Pedestr ian barr ier Pedestrian barriers should be provided on both sides of pedestrian bridges and on the outside edges of highway bridge sidewalks separated from the roadway by a traffic barrier. Pedestrian barriers should be in accordance with the minimum height requirements which are given in Table 12.5.2.2 in CAN/CSA-S6-00, as aforementioned in chapter 3.1 Traffic barrier. Openings in pedestrian barriers should not exceed 150 mm in the least direction, or be covered with chain link mesh with a minimum wire diameter of 3.5 mm and openings smaller than 50 mm by 50 mm. precast concrete barriers in British Columbia.doc Co lumbia.doc

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The design loading for pedestrian barrier are given in Section 3.8.8, Barrier Loads, in CAN/CSAS6-00 (see Table 1 – Traffic barrier loads, from Figure 3.8.8.1, CAN/CSA-S6-00). These loads should be applied as shown in the beneath figure (the design load application for pedestrians and bicycle are the same). When designing posts of post and railing barriers only one railing should be loaded at a time.

Figure 3 – The application of pedestrian and bicycle design loads to barriers, from Figure 12.5.3.2, CAN/CSA-S6-00

3.3 3.3 Bicy cle barrier Bicycle barriers should be provided on both sides of bicycle bridges and on the outside edges of highway bridge bikeways where the bikeway is separated from the roadway by a traffic barrier. Bicycle barriers should also conform c onform the minimum height h eight requirements requ irements which are given in Table 12.5.2.2 in CAN/CSA-S6-00, as aforementioned aforementioned in chapter 3.1 Traffic barrier. Openings in bicycle barriers for the lower 1050 mm should be smaller than 150 mm in the least direction, or be covered with chain link mesh with a minimum wire diameter of 3.5 mm and openings smaller than 50 mm by 50 mm. The design loading for bicycle barrier are given in Section 3.8.8 in CAN/CSA-S6-00, Barrier Loads. Since the design load application for pedestrians and bicycle are the same, the loads should be applied as shown in Figure 3 – The application of pedestrian and bicycle design loads to barriers, from Figure 12.5.3.2, CAN/CSA-S6-00. When designing posts of post and railing barriers only one railing should be loaded at a time.


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3.4 Combinatio n barrier Combination barriers shall be provided on the outside edges of bridge sidewalks and bikeways not separated from the traffic lanes by traffic barrier. They should meet the requirements mentioned in chapter 3.1 Traffic barrier, 3.2 Pedestrian barrier, and 3.3 Bicycle barrier except in respect of geometry and the openings. In combination barriers opening shall be smaller than 150 mm in the least direction for the lower 600 mm of the barrier and 380 mm in the least direction above the lower 600 mm of the barrier.


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4. Lit eratur e review of backgr ound to CHBDC requirements of b ridg e barriers and other backgrou nd regardin g br idge barriers and barrier testing 4.1 The precur sor of the Canadian High way Brid ge Design Code The CAN/CSA-S6-00 Canadian Highway Bridge Design Code amalgamates and supersedes both, CAN/CSA-S6-88 Design of Highway Bridges and the OHBDC-91-01 Ontario Highway Bridge Design Code, third edition, becoming the standard National Code used in Canada. CAN/CSA-S6-88 Design of Highway Bridges is prepared by the Canadian Standards Association (CSA) for highway bridge design in Canada and the OHBDC-91-01 Ontario Highway Bridge Design Code was published by the Ontario Ministry of Transportation, Downsview, Ontario. Therefore, reviews of the CAN/CSA-S6-88 Design of Highway Bridges as well as the OHBDC-91-01 Ontario Highway Bridge Design Code are presented and in addition the main changes of the precursor compared to the CAN/CSA-S6-00 Canadian Highway Bridge Design Code are outlined.

4.1.1 Review of CAN/CSA-S6-88 requirements of bridge barriers In Section 4.4 of the CAN/CSA-S6-88 Design of Highway Bridges barriers named roadway railings are defined. The type of barrier is due to its function defined as traffic railing, sidewalk railing, bicycle railing, and combination railing. The different types of railings which should be illustrative only are shown in Figure 3, CAN/CSA-S6-88 , with its dimensions and design loads. All bridges should have a railing on each side. Roadway railings are covered in Section 4.4.2. The first subsection, Section 4.4.2.1, deals with the geometry and defines that the rail on the traffic side should have a smooth and continuous face of rail. The next section deals with joints and says that provisions should be made where expansion joints interrupt the continuous railings to transfer the loads. The endings of railings should be treated with caution and are covered in Section 4.4.2.3. Concerning the design of traffic railings, Section 4.4.2.4 outlines a height of minimum 700 mm, except that parapets with sloping traffic faces are used which demands a minimum height of 800 mm. The height is measured from the top of the roadway, the top of future overlay, or the top of the curb to the top of the upper rail members. The lower element of a roadway or combination railing should consists of a parapet projecting at least 600 mm above the reference surface, or a participating curb (Section 4.4.2.5). The next section defines the maximum opening below the lower rail, or between succeeding rails to a maximum of 380 mm.


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The height of sidewalk and bicycle railings should be as indicated in Figure 3, CAN/CSAS6-88 . Beside that, sidewalk railings should have a maximum opening of 150 mm in least dimension (Section 4.4.3, CAN/CSA-S6-88 ). Concerning combination railings, governed in Section 4.4.4 of CAN/CSA-S6-88 , the minimum height of combination railings is 1000 mm. The design of the roadway railings, parapets, and posts, as laid out in Section 5.2.10.4 in CAN/CSA-S6-88 , should be done with transverse loads given for some railing types (see Figure 3, CAN/CSA-S6-88 ). Sidewalk, bicycle, and combination railings should be designed for transverse and vertical loads on each longitudinal member, simultaneously (see Section 5.2.10.4.2 to 5.2.10.4.4, CAN/CSA-S6-88 ).

4.1.2 Comments on changes between CAN/CSA-S6-88 and CAN/CSA-S6-00 The requirements on the geometry of the barriers has only little changes. But the definition of the height of a barrier as well as the design requirements underlie many chan ges. Traffic railings are not differentiated due to different site conditions of a bridge site which is done with the Performance Level in the new Code, CAN/CSA-S6-00. Under Section 4.4.2.4 of CAN/CSA-S6-88 a minimum height of the roadway railing is defined by 700 mm which is comparable with the height of PL-1 given in CAN/CSA-S6-00. But on the other side, CAN/CSAS6-88 gives a minimum opening of 380 mm for traffic barriers which does not exists any more in CAN/CSA-S6-00. Another point which is new in CAN/CSA-S6-00 are the anchorages of the roadway railings and their design. Since the aspect of failure became a bigger role in the design, because of the changes of the power of cars, traffic barriers and their design changed. They should nowadays also provide a reduction of the consequences of a vehicle leaving the roadway due to the occurrence of an accident. The requirements on the geometry of pedestrian, bicycle, and combination barriers has changed only little too. CAN/CSA-S6-00 describes the requirements on the geometry more detailed and more separated due to its function. The requirements on the design of pedestrian, bicycle, and combination barriers are no more as detailed as they were before, but therefore crash test requirements are defined. In the end it can be said that CAN/CSA-S6-88 gives a great flexibility in the design of roadway railings. For some cases the design loads are given but it is mentioned that they are only illustrative. Therefore a definition of the design of other types of railings is missing. Crash tests to determine the effectiveness in reducing the consequences of vehicles leaving the roadway upon the occurrence of an accident are not considered at all.

4.1.3 Review of OHBDC-91-01 requirements of bridge barriers In Section 5 of the OHBDC-91-01, third edition, barriers and highway appurtenances are defined. In general, barriers are design at superstructure sides or edges and are supposed to help to restrain errant vehicles from leaving the roadway as mentioned in Section 5-4.1, OHBDC-91-01. Barriers are differentiated due to their location and function in traffic, precast concrete barriers in British Columbia.doc

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combination, pedestrian, and bicycle barriers. The barrier alignment, as defined in Section 5-4.1.3, OHBDC-91-01, Barrier Geometry , should be continuous and smoothly transitioned. The expansion joints that allow for bridge flexure and thermal movements should be designed in detail for all barrier types. The minimum barrier heights are defined in Table 5-4.1.3.2, OHBDC91-01 and come up to 0.70 m, 0.80 m, and 1.05 m for PL 1, 2, and 3 traffic barriers respectively. In Section 5-4.2, OHBDC-91-01, superstructure side barriers are defined. Within that section it is mentioned that traffic barriers should conform to the relevant Performance Levels PL-1, PL-2, or PL-3 in accordance with the crash testing procedures of the AASHTO Guide Specifications for Bridge Railings, 1989. The Performance Level selection, defined in Section 5-4.3, OHBDC-91-01, is based on the barrier exposure index, BI. And the barrier exposure index is based on the first year annual daily traffic (ADTi) and corrected by factors concerning the highway type, curvature, grade, and the height of superstructure. With a calculated barrier exposure index the Performance Level can be determined together with the design speed, percentage of trucks using the highway, and the barrier clearance (see Tables 5-4.3.2.2(a) to (c), OHBDC-91-01). The barrier appraisal due to traffic barrier acceptance and selection are defined in Section 5-4.4.2, OHBDC-91-01. Traffic and combination barriers which conform the geometry and strength of the prototypes that have been tested and appraised in accordance with AASHTO Guide Specification for Bridge Railings, 1989, are accepted directly. Barrier transitions should be crash tested and approved in accordance with NCHRP Report 230: Recommended Procedures for the Safety Performance Evaluation of Highway Appurtenances, to be accepted. Barriers and barrier transitions, which do not meet the conditions as defined in the aforementioned paragraph, but have similar geometry to that of a specific barrier that has been crash tested, may be used if three conditions which are mentioned in Section 5-4.4.2.2 (a) to (c), OHBDC-91-01, are met. Pedestrian and bicycle barriers have more detailed definitions about spacing between barriers and openings of the barriers themselves in the sections 5-4.5.2, and 5-4.5.3, OHBDC-9101, respectively. The design loads should be applied as shown in the following figure:

Figure 4 – Application of pedestrian loads for pedestrian railings, from Figure 5-4.5.2.3,


OHBDC-91-01

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Figure 5 – Application of pedestrian loads for bicycle railings and combination barriers, from Figure 5-4.5.2.3, OHBDC-91-01

4.1.4 Comments on changes between OHBDC-91-01 and CAN/CSA-S6-00 The OHBDC-91-01 was definitely the basis for the development of CAN/CSA-S6-00. There are only little changes in the contents as well as in the sequence. The requirements on the geometry have almost no changes. The minimum heights of the barriers are approximately the same in the OHBDC-91-01 and CAN/CSA-S6-00. But there are some changes in the values which are used in the determination of the Performance Level. The correcting factors, to calculate the Performance Level, are in average higher in OHBDC-91-01, but the range is still the same. But besides that, the tables which result to the Performance Level are based on higher values of the barrier exposure index (BI). And, in the end, it can be said that the Performance Level results in both Codes, the OHBDC-91-01 and CAN/CSA-S6-00, in average in the same Levels, although the values used for the determination are different. Another point that is different in CAN/CSA-S6-00 is that it accepts alternative Performance Levels whereas the OHBDC-91-01 only accepts the Performance Levels PL-1, PL2, and PL-3. The design of the traffic barriers is based on some prototypes and there geometry in OHBDC-91-01. Crash testing can be waived for barriers that have a successful in-service performance record which makes the design very fast. But nevertheless OHBDC-91-01 does not precast concrete barriers in British Columbia.doc

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mention any requirements for the traffic barrier anchorages which are the basis in helping to restrain errant vehicles from leaving the roadway. The design of pedestrian and bicycle barriers, as well as combination barriers is very similar in the OHBDC-91-01and the CAN/CSA-S6-00.

4.1.5 General co mment o n th e changes of the CHBDC to the pr ecurso r Finally, it can be said that Section 12 of CAN/CSA-S6-00 Canadian Highway Bridge Design Code, Barriers and Highway Accessory Supports, is based on OHBDC-91-01 Ontario Highway Bridge Design Code, third edition. The composition of the twelfths Section of CAN/CSA-S6-00 is more or less the same than in the OHBDC-91-01. But Section 12 of CAN/CSA-S6-00 carriers forward the crash testing requirements for barriers that appeared in OHBDC-91-01. And crash testing may be waived for barriers that have a successful in-service performance record. Section 12 of CAN/CSA-S6-00 also propels forward the aspect of alternative Performance Levels.

4.2 Other backgro und literature regarding the CHBDC Concerning the design of the barriers the CAN/CSA-S6-00 Canadian Highway Bridge Design Code as well as the precursor refer several times to the AASHTO (American Association of State Highway Transportation Officials) Guide Specifications for Bridge Railings . In 1989 AASHTO published Guide Specifications for Bridge Railings, which contains the recommendations and procedures to evaluate bridge railings by full-scale vehicle crash testing. In rd 2004, the 3 Edition and therefore the newest AASHTO LRFD (Load and Resistant Factor Design) Bridge Design Specifications was published and deals in section 13 with bridge railings. This section describes three bridge-railing Performance Levels and associated crash tests and performance requirements plus guidance for determining the appropriate railing Performance Level for a given bridge site. Concerning full-size crash tests the CHBDC as well as the AASHTO refers to Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. This report was published by the NCHRP (National Cooperative Highway Research Program) in 1993. It presents a uniform guideline for crash testing of both, permanent and temporarily highway safety features and recommended evaluation criteria to assess test results. Due to the importance of AASHTO LRFD Bridge Design Specifications and NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features even in Canada, the guides itself as well as their backgrounds are presented.


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4.2.1 AASHTO LRFD Bridge Design Specifications, Section 13, Railings, from 1997 In section 13 of AASHTO AASHTO LRFD Bridge Design Specifications railings which should be provided along the edges of structures for protection of traffic and an d pedestrians are defined. The guideline indicates the application of four types of rails including which are: (1) traffic railing, (2) pedestrian railing, (3) bicycle railing and (4) combination railing. A traffic railing is used when a bridge is for the exclusive use of highway traffic whereas a combination barrier is used on low-speed highways in conjunction with a raised curb and sidewalk and on high-speed highways where the pedestrian or bicycle path should have both, an outboard pedestrian or bicycle railing, respectively, and an inboard combination railing.

4.2.1.1 Traffic railings In general, the primary purpose of traffic railings is to contain and redirect vehicles using the structure and that means that they should be crashworthy, which means a system is successfully crash-tested). When choosing traffic railings the following aspects should be considered:

• • • • • •

Protection of the occupants of a vehicle in collision with the railing; Protection of other vehicles near the collision; Protection of persons and property on roadways and other areas underneath the structure; Possible future rail upgrading; Railing cost-effectiveness; and Appearance and freedom of view from passing vehicles.

An approach guardrail system, including a transition from the guardrail system to the rigid bridge railing system, should be provided at the beginning and end of all bridge railings in high speed rural areas. Depending on the chosen performance level the corresponding testing criteria as the weight of the vehicles, speed, and angle of impact are defined and can be found in the following table:


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Table 2 – Bridge railing Performance Levels and crash test criteria from Table 13.7.2.1, AASHTO LRFD Bridge Design Specifications, 1997

Concerning the design, a crashworthy railing system, which is a system that is crash tested and afterwards accepted, may be used without further analysis provided that the proposed installation features are the same. New railing systems may be used, provided that acceptable performance is demonstrated through full-scale crash tests which can be b e tested with the NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features) or that crash test specimens for a railing system is designed to resist the applied loads in accordance with Appendix A of AASHTO LRFD Bridge Design Specifications (see chapter 4.2.3 Appendix A of AASHTO LRFD Bridge Design Specifications). The minimum edge thickness for concrete deck overhangs should be 8 inches for concrete deck overhangs, either supporting a deck-mounted post system or supporting concrete parapets or barriers, and 12 inches for a side-mounted post system. The height of concrete railings should be at least 32 inches for PL-2 and 42 inches for PL-3. For future overlay considerations the bottom 3-inches lip of the safety shape should not be increased. The minimum height for a concrete parapet with a vertical face is 27 inches which applies also to combined concrete and metal railings. The geometry of the railing should provide a smooth and continuous face of rail on the traffic side.

4.2.1.2 Pedestrian railings The pedestrian railing should be at least 42 inches high measured from the top of the walkway. And the clear opening applied to the lower 27 inches should be less than 6 inches between rail elements and above the 27 inches less than 15 inches between rail elements. The design live loading for pedestrian railing should be w = 0.05 KLF, both transversely and vertically, acting simultaneously on each longitudinal element. The application of the loads is shown in the beneath picture.

Figure 6 – Pedestrian railing loads, from Figure 13.8.2.1, AASHTO LRFD Bridge Design Specifications


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4.2.1.3 Bicycle railings The bicycle railing should be at least 54 inches high, measured from the top of the riding surface. The height of the upper and lower zones of bicycle railing should be at least 27 inches. The design live loading for bicycle railing should be w = 0.05 KLF, both transversely and vertically, acting simultaneously on each longitudinal element for rail heights under 54 inches. If the rail is higher than 54 inches, the designer has to determine the design loads himself. The application of the loads is shown in the beneath picture.

Figure 7 – Bicycle Railing Loads, from Figure 13.9.3.1, AASHTO LRFD Bridge Design Specifications

4.2.1.4 Combination railings The requirements of either the pedestrian or the bicycle railings, whichever is applicable, should be used for the design of the combination railing.

4.2.2 AASHTO LRFD Bridge Design Specifications, Section 13, Railings, 2004 2004:: Impor tant ch anges from the 2 nd to the 3 rd Edition The important changes from the second to the third edition of AASHTO AASHTO LRFD Bridge Design Specifications are mainly in the traffic railing chapter.


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The testing criteria are no more chosen due to a selected Performance Level, they are chosen due to a selected Testing Level. It is the responsibility of the user agency to determine which of the test levels is the most appropriate for the bridge site. The Testing Levels are defined as the following:

•

Testing Level 1 (TL-1) taken to be generally acceptable for work zones with low posted speeds and very low volume, low speed local streets:

•

Testing Level 2 (TL-2) taken to be generally acceptable for work zones and most local and collector roads with favourable site conditions as well as where a small number of heavy vehicles is expected and posted speeds are reduced;

•

Testing Level 3 (TL-3) taken to be generally acceptable for a wide range of high-speed arterial highways with very low mixtures of heavy vehicles and with favourable site conditions

•

Testing Level 4 (TL-4) taken to be generally acceptable for the majority of applications on high speed highways, freeways, expressways, and Interstate highways with a mixture of trucks and heavy vehicles;

•

Testing Level 5 (TL-5) taken to be generally acceptable for the same applications as TL4 and where large trucks make up a significant portion of the average daily traffic or when unfavourable site conditions justify a higher level of rail resistance; and

•

Testing Level 6 (TL-6) taken to be generally acceptable for applications where tankertype trucks or similar high center of gravity vehicles are anticipated, particularly along with unfavourable site conditions.

The testing criteria such as vehicle weights, vehicle speeds, and angles of impact are given in the following table for a chosen Testing Level:

Table 3 – Bridge railing Testing Levels and crash test criteria, from Figure 13.7.2-1, AASHTO LRFD Bridge Design Specifications 2004


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The height of concrete railings should be at least 27 inches for TL-3, 32 inches for TL-4, 42 inches for TL-5, and 90 inches for TL-6. For future overlay considerations the bottom 3-inches lip of the safety shape should not be increased. The minimum height for a concrete parapet with a vertical face is 27 inches which applies also to combined concrete and metal railings. The geometry of the railing should provide a smooth and continuous face of rail on the traffic side.

4.2.3 Appendix A of AASHTO LRFD Bridge Design Specifications, 1997 In Appendix A the design of barriers and the specimens are explained in detail. The geometry and anchorages are explained first in chapter A13.1. Then, in chapter A13.2 traffic railing design forces and in chapter A13.3 design procedures for railing test specimens, divided into concrete railings, post-and-beam railings, combination concrete parapet and metal rail, and wood barriers, are defined. The last chapter in the appendix, A13.4, deals with deck overhang design.

4.2.3.1 Geometry and Anchorages Traffic railings have a defined setback distance S which recognizes the tendency for various shape posts to snag wheels. The implication of the various definitions of the setback distance S is that all other things being equal the space between a rail and the face of a rectangular post will be greater than the distance between a rail and the face of a circular post.

Figure 8 – Geometrical definitions of two typical traffic railings, from Figure A13.1.1-1, AASHTO LRFD Bridge Design Specifications

For post railings, the combination of ratio of rail contact width to height (∑A/H) and the post setback distance S, should be within or above the shaded area of the following figure:


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Figure 9 – Post setback criteria, from Figure A13.1.1-3, AASHTO LRF D Bridge Design Specifications

The reinforcing steel for concrete barriers should have a sufficient embedment length which is defined in Section 5 in AASHTO LRFD Bridge Design Specifications to develop the necessary yield strength.

4.2.3.2 Traffic Railing Design Forces The railing design forces and geometric criteria that are used for developing test specimens for a crash test program are defined in this chapter. The effective height of the vehicle rollover force, He, should be taken taken as: H e = G -

WB 2Ft

Where: G = Height of vehicle center of gravity above bridge deck (FT) W = Weight of vehicle corresponding to the required Performance Level (KIP) B = Out-to-out wheel spacing on an axle (FT) Ft = Transverse force corresponding to the required Performance Level (KIP)


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Figure 10 – No menclature for traffic railing equations, from Figure CA13.2.1, AASHTO LRFD Bridge Design Specifications, 1997

And the railings should be proportioned so that:

∑ R

•

R ≥ Ft , for which R =

•

Y ≥ H e , for which Y=

i

∑ (R Y ) i

i

R

Where: R i = Resistance of the rail (KIP) th

Yi = Distance from bridge deck to the i rail (FT) The transverse and longitudinal loads have to be applied in conjunction with vertical loads as given in the figure below. All the forces should be applied to the longitudinal rail elements. The distribution of longitudinal loads to posts should be consistent with the continuity of rail elements and the transverse loads with the assumed failure mechanism of the railing system.


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Figure 11 – Design forces for traffic railings, from Table A13.2-1, AASHTO LRFD Bridge Design Specifications, 1997

To understand the application of the design loads better they are presented, for example, on a metal bridge railing which can be seen in the beneath figure.

Figure 12 – Railing design forces, from Figure A13.2-1, AASHTO LRFD Bridge Design Specifications

4.2.3.3 Design Procedures for Railing Test Specimens A design procedure for reinforced concrete and prestressed concrete railing or parapet test specimens is the yield line analysis and strength design. The yield line analysis includes the ultimate flexural capacity of the concrete component. Stirrups or ties should be able to resist the shear and the diagonal forces if present. In the yield line analysis it is assumed that the yield line failure occurs only in the parapet and does not extend to the deck. That means that the decks need a sufficient resistance to force the yield line failure pattern to remain within the parapet.


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The nominal railing resistance to transverse load, R W, can be determined using the yield line approach as the following:

•

⎛ 2 ⎞⎛ Mc Lc 2 ⎞ RW =⎜ ⎟⎜ 8M b +8M w H+ ⎟ 2L -L H ⎠ ⎝ c t ⎠⎝

For impacts within a wall segment:

where the critical wall length is:

•

⎛L ⎞ LC = ⎜ t ⎟ ⎝ 2⎠

For impacts at the end of wall or joint:

where the critical wall length is:

⎛ ⎛ L t ⎞2 8H(M b +M w H) ⎞ ⎜⎜ ⎜ ⎟ + ⎟⎟ 2 M ⎝ ⎠ c ⎝ ⎠

⎛ 2 ⎞⎛ M c Lc 2 ⎞ RW =⎜ ⎟⎜ M b +M w H+ ⎟ 2L -L H ⎠ ⎝ c t ⎠⎝

⎛L ⎞ LC = ⎜ t ⎟ ⎝ 2⎠

⎛ ⎛ Lt ⎞2 ⎛ M b +M w H ⎞ ⎞ + H ⎜⎜ ⎜ ⎟ ⎜ ⎟ ⎟⎟ 2 M ⎝ ⎠ c ⎝ ⎠⎠ ⎝

Where: R w = Total transverse resistance of the railing (KIP) Lt = Longitudinal length of distribution of impact force Ft (FT) M b = Additional flexural resistance of beam in addition to Mw, if any, at top of wall (KFT) Mw = Flexural resistance of the wall (KFT/FT) H = Height of the barrier (FT) Mc = Flexural resistance of cantilevered wall (KFT/FT) The yield line analysis is explained in the following figures. The first figure shows the explanation of the lengths for a wall segment and for a near the end of wall segment. The second figure shows the where and in which direction the moments occur.

Figure 13 – Yield Line Analysis of concrete parapet walls for impact within wall segment and near end of wall segment, part 1 of Table A13.3.1-1/2, AASHTO LRF D Bridge Design Specifications precast concrete barriers in British Columbia.doc

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Figure 14 – Yield Line Analysis of concrete parapet walls for impact within wall segment, part 2 of Table A13.3.1-1, AASHTO LRFD Bridge Design Specifications

For a combination concrete parapet with metal rail, the resistance of each part has to be determined first, separately. The resistance of the concrete parapet should be determined as explained in the paragraph before with the yield line analysis. The nominal resistance R of the metal railing is the result of possible yield failure modes for post-and-beam railings. The basis of the failure modes are shown in the figures on the next page.

Figure 15 – Possible failure modes for post-and-beam railings, from Table A13.3.2-1, AASHTO LRFD Bridge Design Specifications


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The critical wall nominal resistance, R, for the metal railing should be the least value determined by the following two equations for various numbers of railing spans N:

•

For failure modes involving an odd number of railing spans N: R=

•

16M p + (N-1)(N+1)Pp L 2NL-L t

For failure modes involving an even number of railing spans N: R=

16M p + N 2 Pp L 2NL-L t

Where: R = Total ultimate resistance, i.e. nominal resistance, of the railing (KIP) M p = Inelastic or yield line resistance of all of the rails con tributing to a plastic hinge (KFT) N = Number of railing spans (-) P p = Ultimate transverse load resistance of a single post located Y above the deck (KIP) L

= Post spacing or single-span (FT)

Lt = Longitudinal length of distribution of impact force Ft (FT) The flexural strength of the combination rail, R , should be determined over one span, R R , and over two spans, R'R . The resistance of the post on the wall, PP, shall be determined including the resistance of the anchor bolts or post. The resistance of the combination parapet with rail is the lesser resistance determined for the two failure modes, impact at mid-span and impact at post, respectively. The failure modes are shown in a figure after the equations on the next page.

•

•

Where the impact is at mid-span: The combined resultant strength is:

R = R R + R W

and the effective height is:

Y=

R R HR + R W HW R

Where the impact is at a post: The combined resultant strength is:


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and the effective height is:

for which R'W =

R W H W - PP HR

Y=

PP H R + R'R H R + R'W H W R

HW

Where: R

= Flexural strength of the combination rail (KIP)

R R

= Ultimate capacity of rail over one span (KIP)

R W

= Ultimate capacity of wall (KIP)

Y

= The effective height (FT)

HR

= Height of wall (FT)

HW

= Height of rail (FT)

PP

= Resistance of the post on the wall (KIP)

R'R = Ultimate transverse resistance of rail over two spans (KIP) R'W = Capacity of wall, reduced to resist post load (KIP)

Figure 16 – Combination concrete wall and metal rail evaluation-impact at (1) mid-span of rail and (2) at a post, from Table A13.3.3-1/ 2, AASHTO LRFD Bridge Design Specifications


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4.2.4 Appendix A of AASHTO LRFD Bridge Design Specifications, 2004: Important changes fr om the 2 nd to the 3rd Edition The important changes from the second to the third edition of AASHTO LRFD Bridge Design Specifications are only in the chapter Traffic Railing Design Forces. The table giving the design forces for traffic railings changed due to the change from performance Levels to Testing Levels. The new table is the following:

Table 4 – Design forces for traffic railings, from Table A13.2-1, AASHTO LRFD Bridge Design Specifications, 2004

4.2.5 NCHRP Report 350: Recom mended Pro cedures for the Safety Perfo rmance Evaluation o f Highway Featur es Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features was published by the National Cooperative Highway Research Program (NCHRP) in 1993 and is an all-metric document. This report replaced NCHRP Report 230: Recommended Procedures for the Safety Performance Evaluation of Highway Appurtenances, which was published in 1981.

In Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features recommended procedures for evaluating the safety performance of various highway safety features are contained. The features covered by these procedures include (1) longitudinal barriers such as bridge rails, guardrails, median barriers, transitions, and terminals; (2) crash cushions; (3) breakaway or yielding supports for signs and luminaries; (4) breakaway utility poles; (5) truck-mounted attenuators; and (6) work zone traffic control devices. The approach of the report was to normalize test conditions. And therefore the test parameters as the testing facility, the test article, and the test vehicle are defined. Report 350 includes six different Test Levels (TL-1 through TL-6) for various classes of roadside safety features, and a number of optional test levels to provide the basis for safety evaluations to support more or less stringent performance criteria. Although this document does not include objective criteria for relating a test level to a specific roadway type, the lower test levels generally are intended for use on roadways with lower service levels and certain types of work zones, whereas the higher test levels are intended for use on higher-service-level roadways. precast concrete barriers in British Columbia.doc

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For vehicle crash tests, specific impact conditions such as vehicle mass, speed, approach angle, and point on safety feature to be hit are presented. The test matrices including standard tests as well as the standard test vehicle types are described. To evaluate the crash test performance, three primary appraisal factors as structural adequacy, occupant risk, and aftercollision vehicle trajectory are presented. Depending on the safety feature's function, it should contain, redirect, and permit controlled penetration of the impacting vehicle, or permit a controlled stop in a predictable manner to satisfy structural adequacy requirements. In addition the report reflects a critical review of methods and technologies for safety performance evaluation, such as surrogate test vehicles and computer simulations, and incorporates state-of-the-art methods in the procedures. In-service evaluation of extensively modified roadside safety features are used with the purpose of appraising actual performance during a broad range of collision, environmental, operational, and maintenance situations for typical site and traffic conditions.

4.3 Other literature regarding brid ge barriers and barri er testing There exist many literatures dealing with bridge barriers and their testing. A summary of the paper "Basics of Concrete Barriers" published by Charles F. McDevitt is given to get a general introduction to barriers and their shapes. And to get a comparison to the Codes used in the Province of British Columbia to another country, the state of Washington in the United States of America has been chosen. Washington state is the neighbour state of British Columbia which means that they deal with the same climate conditions. And in addition, many of the barriers and anchors used in British Columbia are compared to the United States of America. Hence, the Washington State Bridge Design Manual which is the bridge design code of the state Washington in the United States of America, is presented and a comment on the Manual is given.

4.3.1 Basics of Concrete Barriers The basic principles of concrete barriers are not generally known and easy to understand and therefore this chapter gives a short introduction explaining the reasons for the shape of a barrier. Concrete barriers appear to be simple and uncomplicated, but in reality they are sophisticated safety devices. This chapter represents a summary of the paper "Basics of Concrete Barriers" published by Charles F. McDevitt who is a structural engineer in the Federal Highway Administration's Office of Safety Research and Development at the Turner-Fairbank Highway Research Center in McLean. The most well-known barrier in the United States of America is the New Jersey Concrete Safety Shape Barrier, also called NJ-shape or Jersey barrier. Since some problems occurred in the 1970's, a parametric study with systematically varying the parameters of various configurations that were labelled A through F was done. The result was that configuration F performed distinctly better than the NJ-shape. The results of these computer simulations were confirmed by a series of full-scale crash tests and configuration F became known as the F-shape barrier. The slope of the precast concrete barriers in British Columbia.doc

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F-shape and the NJ-shape barrier are the same, but the major difference is the distance from the ground to the slope break point. This distance is 255 mm for the F-shape barrier which is 75 mm lower than the NJ-shape one. The lower slope break point significantly reduced the lifting of the vehicle and greatly improved the performance of the concrete barrier. The key design parameter for a safety shape profile is the distance from the ground to the slope break point because this determines how much the suspension will be compressed. For example for the NJ-shape barrier, this distance is 330 mm (13 inches). The front bumper impacts the upper sloped face and slides upwards. This interaction initiates lifting of the vehicle. When a concrete safety shape lifts a vehicle, some of the kinetic energy of the vehicle is converted to potential energy. This potential energy is turned back into kinetic energy as the vehicle returns to the ground. If the bumper is relatively weak, the front end starts to crush before any uplift occurs. Then, as the vehicle becomes more nearly parallel with the barrier, the wheel contacts the lower slope face. Most of the additional lift of the vehicle is caused by the lower sloped face compressing the front suspension. However, wheel side-scrubbing forces provide some additional lift, particularly if the barrier face is rough. Therefore, exposed aggregate and other rough surface finishes should be avoided. Drainage openings in the face of the reveal do not have a significant effect on an impacting vehicle. Vertical concrete parapets do not have the energy management feature as described in the paragraph before. But crash tests have demonstrated that they can perform acceptable as traffic barriers. All of the energy absorption in an impact with a rigid vertical parapet is due to crushing of the vehicle. Bumpers usually do not slide up vertical concrete parapets and lift the vehicle, so all four wheels tend to stay on the ground. This minimizes the potential for vehicle rollover. Finally, it can be said that each of these barrier types fills a niche and helps meet the needs of highway agencies that select, design, and locate traffic barriers. In terms of safety performance, the 1070 mm (42 inches) high F-shape is currently the best technology in the United States of America. The F-shape profile is clearly superior to the NJ-shape and is gradually being used by more jurisdictions for both portable concrete barriers and permanent barriers.

4.3.2 Review of the Washington State Bridge Design Manual The Washington State Bridge Design Manual (WSBDM) M 23-50 was published by the Washington State Department of Transportation (WSDOT), Program Development Division, Bridge and Structures, in August 2006. The Washington State Bridge Design Manual supplements the AASHTO LRFD Bridge Design Specifications by providing additional direction, design aides, examples, and information on office practice. Bridge Barriers can be found in Chapter 10 of the Washington State Bridge Design Manual. In particular, the traffic barriers, are outlined in Chapter 10.2 of the Washington State Bridge Design Manual. This chapter is divided into four topics which are (1) General guidelines, (2) Bridge railing Test Levels, (3) Available Washington State Department of Transportation Designs, and (4) Design Criteria.


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The general guideline defines the Test Level, which is for bridge barriers in Washington State TL-4. And in addition the section Bridge and Structures defines the 32-inch high F-Shape concrete barrier as the standard barrier. This barrier should be used on all interstate, major highway routes, and over National Highway System (NHS) routes. A Single Slope bridge barrier is allowed if there is a Single Slope concrete barrier on the approach grade to a bridge or for continuity within a corridor and has to be at least 34-inches high. Bridge traffic barriers of a height of 42-inches should be used on interstate or freeway routes only in the special cases as (1) accidental history suggest a need, (2) large trucks make up a significant portion of the barrier exposure index (ADT), (3) adverse roadway geometrics increase the possibility of hitting the traffic barrier at a high angle, and (4) protection of schools, businesses or other important facilities below the bridge. The bridge railing Test Levels should be, appropriately to NCHRP Report 350, six different bridge railing test levels, TL-1 through TL-6, and associated crash test and performance requirements are given. The available Washington State Department of Transportation designs of traffic barriers for TL-4 are Shape F and Single Slope barriers. The Shape F barrier was developed in the 1960's, but recently tested at TL-4 under NCHRP Report 350. The height of the traffic barrier is 32 inches. The Single Slope barrier was designed by the state of California in the 1990's and recently tested at TL-4 under NCHRP Report 350. The height of the traffic barrier was increased from 32 inches to 34 inches to match the approach traffic barrier height.

Figure 17 – Detail drawing of the F-shape and Single Slope barrier, WSDoT, WSBDM, Figure 10.2.3-2

The available Washington State Department of Transportation designs for traffic barriers for TL-5 are Shape F 42-inches, and Single Slope 42-inches. The Shape F 42" barrier as well as the Single Slope 42" barrier are very similar to the 32-inch F-shape and Single Slope concrete barrier, respectively. The barriers have been crash tested for a 50,000 lb. tractor trailer. The Single Slope 42" barrier offers a simple to build alternative to the Shape F configuration.


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The Washington State Department of Transportation traffic barriers are reinforced, based on the Federal Highway Administration (FHWA) crash testing program as described in NCHRP Report 350 and should not be significantly modified. Because it is based on the AASHTO LRFD Bridge Design Specifications 10 kip load, the traffic barriers are overdesigned. To prevent this overdesign the nominal traffic barrier resistance to transverse load, R W, need not to be taken 120% of the design force. The deck overhang should be design in accordance with AASHTO LRFD Bridge Design Specifications Section A 13.4.2 providing a flexural resistance MS, acting coincident with the tensile force T. At the inside face of the barrier the flexural resistance, MS, should be taken as:

•

For an interior segment:

MS =

•

For an end segment:

MS =

RW H L C +2H RW H LC + H

and

T=

and

T=

R W L C + 2H R W LC + H

Where: MS

= Flexural resistance (KIP)

T

= Tensile force per unit of deck length (KIP/FT)

R W

= Total transverse resistance of the railing (KIP)

H

= Height of wall (FT)

LC

= Critical length of yield line failure pattern (FT)

But MS should be greater than the flexural resistance of the cantilevered wall (MC) at the base. And the barrier impact design forces transmitted to the deck overhang without including the dead loads of the barrier itself as well as the slab, should be taken as:

Table 5 – Vehicle impact loading on traffic barrier by WSDOT, WSBDM, Section 10.2.4, Design Criteria

Concerning the geometry it is mentioned that thickening of the traffic barrier is permitted as long as the concrete cover requirement is met.


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4.3.3 Comment on the Washingt on State Bri dge Design Manual The Washington State Bridge Design Manual gives very precise design provisions and no choice in the design. It allows to use only one particular barrier type which is the F-shape one. In the case of an approaching Single Slope barrier that kind of barrier is allowed as well. The Fshape barrier is one of the most used barriers in the United States of America. It is a modification of the widely-used New Jersey (NJ) barrier design but is generally considered to be safer than the NJ-shape barrier. The barriers are all cast-in concrete bridge barriers whereas precast concrete bridge barriers are not considered at all. It is very interesting to see that the Washington State Department of Transportation (WSDOT) decided to design the barriers different than the AASHTO Bridge Design Specifications, which is in the hierarchy higher, suggests. Since there exists a conflict between the NCHRP Report 350 and the AASHTO Bridge Design Specifications, the Washington State Bridge Design Manual decided to design the barriers following both codes but with restrictions and their own rules.


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5. Lit eratur e review of BC MoT's design lit eratur e regardin g requirements of p recast conc rete brid ge barriers In 2006, the Ministry of Transportation of British Columbia (BC MoT) published the new version of the Standard Specifications for Highway Construction. In section 941, precast reinforced concrete barriers are described and drawings of the barriers are attached to the document. The section covers the quality and manufacture of precast reinforced concrete roadside and median barriers for off-highway traffic confinement use. At the beginning requirements on concrete quality and reinforcing steel are listed and then the placing and finishing of the concrete is described before the procedures for manufactories are explained. The concrete quality should conform CSA Standard CAN3-A23.1-M and the strength is satisfactory if it reaches 30M Pa after 28 days. The reinforcing steel for bent and hooked connections should conform CSA CAN3-G40.21-M Grade 260W and it should be carefully bent to the radii detailed and installed as shown on the Standard Drawings SP941 (see next paragraph). Concrete should be placed in the forms and carefully consolidated in accordance to CSA CAN3-A23.4-M, Clause 19 and the protection and curing should be carried out in accordance with CSA CAN3-A23.4.M, Clause 21. Acceptable tolerances in the concrete dimensions of the barriers is ± 3 mm. Manufactories have to inform the Ministry of Transportation in advance before they produce the barriers so that inspections can be carried out. The payment will be per unit price for a section. The Standard Drawings SP941 attached to the Standard Specifications for Highway Construction can be found in Appendix A and are the following:

Number

Name

SP941-01.01.01 Precast Concrete Bull-Nose 460 mm - CBN-H & CBN-E SP941-01.01.02 Precast Concrete Low Barrier 460 mm - CLB-E+H SP941-01.02.01 Precast Concrete Roadside Barrier 690 mm - CRB-H SP941-01.02.02 Precast Concrete Roadside Barrier 690 mm - CRB-E SP941-01.02.03 Precast Concrete Roadside Barrier 690 mm - CRB-H Details SP941-01.02.04 Precast Concrete Roadside Barrier 690 mm - CRB-E Details SP941-01.02.05 Precast Concrete Drainage Barrier 690 mm - CDB-E Details SP941-02.01.01 Precast Concrete Median Barrier 810 mm - CMB-H SP941-02.01.02 Precast Concrete Median Barrier 810 mm - CMB-E SP941-02.01.03 Precast Concrete Median Barrier 810 mm - CMB-H Details SP941-02.01.04 Precast Concrete Median Barrier 810 mm - CMB-E Details SP941-02.01.05 Precast Concrete Pier Barrier 810 mm - CPB-H SP941-02.01.06 Precast Concrete Pier Barrier 810 mm - CPB-E SP941-02.01.07 Precast Concrete Pier Barrier 810 mm - CP B-H &CP B-E Details precast concrete barriers in British Columbia.doc

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SP941-02.01.08 Precast CRB-H Modifications for Tight Curvature Installation SP941-02.01.09 Precast CRB-E Modifications for Tight Curvature Installation SP941-03.01.01 Precast Concrete Transition Barrier 690 mm to 460 mm - CTB-1E SP941-03.02.01 Precast Concrete Transition Barrier 810 mm to 690 mm - CTB-2H SP941-03.03.01 Precast Concrete Transition Barrier 686 mm to 690 mm - CTB-3H Precast Concrete Transition Barrier 686 mm to 690 mm - CTB-3H SP941-03.03.02 Details SP941-03.03.03 Precast Concrete Transition Barrier 686 mm to 690 mm - CTB-3E+H Precast Concrete Transition Barrier 686 mm to 690 mm - CTB-3E+H SP941-03.03.04 Details SP941-03.04.01 Standard Bridge Parapet 810 mm High Transition SP941-03.04.02 Standard Bridge Parapet 810 mm High Transition - Details SP941-04.01.01 No Post Barrier Anchoring Hardware Precast Concrete Roadside And Median Barriers Shear Key Void SP941-04.02.01 Details Table 6 – List of precast concrete bridge barriers from Section 941, Standard Specifications for Highway Construction, BC MoT


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6.


Review the effect of having int er-connectio n between adjacent precast con crete barriers

The two main connections between adjacent precast concrete bridge barriers will be presented in this chapter. The most typical connection for precast concrete bridge barriers in Canada is the hook and eye system. Depending on the type and size of the barrier the size and shape of the anchors change. The other well known connection between precast concrete bridge barriers is the pin and loop system, mainly used in the United States of America. After the connection types are presented the inter-connection effect between adjacent precast concrete barriers will be analysed.

6.1 The hoo k and eye con nection The hook and eye connection, also called man and female connection, consists of a hook attached to the precast bridge concrete barrier on one side and an eye attached to the barrier on the other side. The anchors which are used in the Standard Specifications for Highway Construction 2006 are shown in the following figure.

Figure 18 – Hooks and eyes, from Standard Specifications for Highway Construction 2006, SP941-04.01.01 precast concrete barriers in British Columbia.doc

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The anchor, used in combination with precast concrete bridge barriers used by the British Columbia Ministry of Transportation (BC MoT), is the following:

Figure 19 – Eye of the BC MoT's precast concrete bridge barrier, from drawing 7780-5

Figure 20 – Hook and eye end section of a barrier in 3D, standard median barrier 810 mm, from drawing SP941-02.01.08 and 09, BC MoT

Figure 21 – Plan view on the end of a hook and eye unit, standard median barrier 810 mm, from drawing SP941-02.01.03 and 04, BC MoT


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Figure 22 – Connection detail (plan view) of the hook (left) and eye (right) system, standard median barrier 810 mm, drawing SP941-02.01.03, BC MoT

The capacity of the anchor depends on the size of the barrier, the size of the bar and the strength of the concrete as well as the bars.

6.2 The pin and loop connection The pin and loop connection consists of six loops (from both barriers, each three) coming out of the precast concrete bridge barrier and one pin going through all the loops put in from the top of the barrier. The loops are 33 inches (838 mm) long and stay only 2 inches (51 mm) out of the concrete. The diameter of a loop is only ¾ inches (19 mm). Whereas the pin has a length of 26 inches (660 mm) and a diameter of 1 inch (25.4 mm). The drawings below will show the pin and loop connection system.

Figure 23 – Plan view of the pin and loop system, from drawing C-8d, Standard Drawings, WSDoT precast concrete barriers in British Columbia.doc

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Figure 24 – The pin in detail, from drawing C-8d, Standard Drawings, WSDoT

Figure 25 – Top and side view of the whole barrier, showing the anchors for the pin and loop system, from drawing C-8d, Standard Drawings, WSDoT


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Figure 26 – View on the end of the barrier, from drawing C-8d, Standard Drawings, WSDoT

6.3 The inter-conn ection effect between adjacent precast barriers One important point is the construction time as well as the easiness of construction on site. The pin and loop system will take more time and have to be more accurate produced to be able to build because the pin has to go through six loops. Whereas the hook and eye connection is easy and fast to build on site although the planned play is not bigger than the one in the pin and loop connection. But the play after construction is bigger in the hook and eye than in the pin and loop connection. Another important point resulting out of the rigidity of the connection of adjacent barriers is in the design. Loads acting on the barriers will be distributed depending on the rigidity of the connection between adjacent barriers on an effective length, depending on the anchorage to the ground. By ignoring the anchorage to the ground, it might be easier to understand the effect of inter-connection between adjacent precast concrete bridge barriers. If the connection between two barriers is stiff, which would mean that a few adjacent barriers are equal to one in the behaviour, the effective length would be really long, even infinity. For a hinged connection the effective length would be the length of one barrier. The connection that is between two adjacent barriers is somewhere between the stiff and hinged connection. It is hard to tell where exactly, but it is definitely closer to the hinged one. The connection that results out of the pin and loop connection is a little bit stiffer than the one of the hook and eye connection due to more connection points of the pin with the loops. When the barriers are designed the effective barrier length is named critical wall length, Lc, (see 4.2.3 Appendix A of AASHTO LRFD Bridge Design Specifications). Finally it can be said that the inter-connection effect can not be ignored in crash tests. The connection between connecting barriers at both ends of one barrier should be simulated to get better results. precast concrete barriers in British Columbia.doc

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7. Compare Brit ish Columbia Ministry of Transportation (BC MoT) anchor age details for precast concr ete bri dge barriers to details by oth er juri sdic tions The anchorage details of precast concrete bridge barriers used by the British Columbia Ministry of Transportation (BC MoT) are presented at the beginning. Then, the results of the search for anchorage details used in combination with precast concrete bridge barriers of other Provinces and Territories of Canada are explained. Since those results were really rare, one anchor type that is used in the United States of America in combination with precast concrete bridge barriers is presented afterwards. At the end a discussion with a comparison between those anchors and the one used in British Columbia is given.

7.1 Anch or details of the MoT of Brit ish Colu mbia The Ministry of Transportation and Highways of the Province British Columbia, Bridge Engineering Branch, is mainly using at the moment three different precast reinforced concrete bolt-down parapets. The drawings of the standard parapets as well as the anch orage details can be found in Appendix B. These three precast barrier types which are differentiated by their heights (810 mm, 865 mm, and 875 mm) are presented in the following subchapters.

7.1.1 The 810 mm high precast c oncr ete bridge p arapet

Figure 27 – 810 mm high precast concrete bridge barrier, from drawing 8023-22, B C MoT precast concrete barriers in British Columbia.doc

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The 810 mm high bridge precast concrete parapet should be in accordance with the M.O.T.H. Specification: Manufacture and Erection of Prestressed Members. The compressive strength of the parapet should exceed a minimum of 50 MPa at 28 days and the concrete surface should have a class 3 finish. And the cover of the reinforcing steel should have a minimum of 50 mm unless noted otherwise. The reinforcing steel should be in accordance with CSA Specification G30.18-M Grade 400R. And the steel designated "ME" means that the steel is epoxy coated. The typical section through the 810 mm high bridge precast concrete parapet with the reinforcement is shown in the following figure. The blockouts are used to put the bolt through into the parapet and screw it into the superstructure. The bolt sleeve can be found below the blockout and reaches down to the bottom of the barrier (dashed lines).

Figure 28 – Typical section through the 810 mm high precast concrete bridge barrier, from drawing 8023-22, BC MoT

The bolt sleeve itself is a HSS 60 x 4.8, 135 mm long sleeve which should conform to CSA Specification CAN3-G40.21-M Grade 350W. To prevent the bolt sleeve to break out of the parapet in case of maximum loading the HSS is connected to a WT 155 x 19.5 steel plate. The plan and elevation view of the bolt sleeve can be seen in the figure on the next page.


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Figure 29 – Bolt sleeve detail of the 810 mm high precast concrete bridge barrier, from drawing 8023-22, BC MoT

The anchor bolt is a 25 mm diameter and 470 mm long bar with both ends threaded. The size of the washer is 10 x 100 x 100 mm. The detail of the anchor bolt itself is shown in the following figure.

Figure 30 – Bolt detail of the 810 mm high precast concrete bridge barrier, from drawing 8023-22, BC MoT


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Figure 31 – 865 mm high precast concrete bridge barrier, from drawing 8023-22, B C MoT

The compressive strength of the parapet should exceed a minimum of 50 MPa at 28 days. And the cover of the reinforcing steel should have a minimum of 50 mm unless noted otherwise. The reinforcing steel should be in accordance with CSA Specification G30.18-M Grade 400 and the steel designated "ME" means that the steel is epoxy coated. A typical section through the 865 mm high precast bridge parapet with the reinforcement is shown in the following figure.

Figure 32 – Typical section through the 865 mm precast parapet, from drawing 2965-4, BC MoT precast concrete barriers in British Columbia.doc

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The blockouts (above the double dashed line) are used to put the bolt through to fasten the parapet to the deck. The faces of the blockout can be sloped minimal to facilitate removal of the formwork. The bolt sleeve is under the blockout and reaches down to the bottom of the barrier.

Figure 33 – Blockout and bolt sleeve detail of the 865 mm high barrier, from drawing 2965-4, BC MoT

The bolt sleeve itself is a HSS 60.3 x 4.78, 190 mm long, and should conform to CSA Specification CAN3-G40.21-M Grade 350W. To prevent the bolt sleeve to break out of the parapet in case of maximum loading the HSS is connected to a WT 155 x 19.5 steel plate. The plan and elevation view of the bolt sleeve can be seen in Figure 34 – Bolt sleeve detail of the 865 mm high barrier, from drawing 2965-4, BC MoT.

Figure 34 – Bolt sleeve detail of the 865 mm high barrier, from drawing 2965-4, BC MoT


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All steelwork, including anchor bolts, nuts and washers, should be galvanized after fabrication, before installation. The anchor bolt can be a 25 mm diameter and 490 mm long bar with both ends threaded for a length of 70 mm. The anchor bolt is shown in detail in Figure 35 – One possible anchor bolt of the 865 mm high precast concrete bridge parapet, from drawing 2965-23, BC MoT. The anchor bolt itself should conform CSA Specification CAN3-G40.21-M Grade 400W and the plate washers should be grade 300W. The size of the two plate washers is 10 x 80 x 80 mm.

Figure 35 – One possible anchor bolt of the 865 mm high precast concrete bridge parapet, from drawing 2965-23, BC MoT


Figure 36 – 875 mm high precast concrete bridge barrier, from drawing 8023-22, B C MoT precast concrete barriers in British Columbia.doc

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The 875 mm high precast concrete barrier should be in accordance with the M.O.T.H. Specification: Manufacture and Erection of Prestressed Members. The compressive strength of the parapet should exceed a minimum of 50 MPa at 28 days and the concrete surface should have a class 3 finish. The cover of the reinforcing steel should have a minimum of 50 mm unless noted otherwise. And the reinforcing steel should be in accordance with CSA Specification G30.18-M Grade 400R. The steel designated "ME" means that the steel is epoxy coated. The typical section through the 875 mm high precast concrete bridge barrier with the reinforcement is shown in the following figure. The blockouts (above the dashed line) are used to put the bolt through and screw it into the anchor bolt. The bolt sleeve starts below the blockout and reaches down to the bottom of the barrier.

Figure 37 – Typical section through the 875 mm high precast concrete bridge barrier, from drawing 7476-12, BC MoT

The bolt sleeve is a HSS 60.3 x 4.78, 190 mm long, and should conform to CSA Specification CAN3-G40.21-M Grade 350W. To prevent the bolt sleeve to break out of the parapet in case of maximum loading the HSS is connected to a WT 155 x 19.5 steel plate. All steelwork, including anchor bolts, nuts and washers, should be galvanized after fabrication, before installation. The anchor bolt itself should conform CSA Specification CAN3-G40.21-M Grade 400W and the plate washers should be grade 300W. The anchor sleeve as well as a detail of the blockout are presented in the following two figures on the next page.


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Figure 38 – Bolt sleeve detail of the 875 mm high precast concrete bridge barrier, from drawing 7476-12, BC MoT

Figure 39 – Blockout and bolt sleeve detail of the 875 mm high barrier, from drawing 7476-12, BC MoT


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7.2 Anch orage details of precast concrete brid ge barriers of other Canadian Provinces and Territories than British Columbia Unfortunately most provinces and territories in Canada, besides British Columbia, did not use precast concrete bridge barriers in the last years. The Ministry of Alberta, division Transportation, is not using precast concrete bridge barriers because of corrosion due to the usage of high amounts of salt during winter time. The few times when precast barriers were used in former times, the experience was that it was very difficult to obtain a good seal between the bridge deck and the precast barriers. Any leakage would cause salt contamination, corrosion, and costly maintenance and repair. The Ministry of Ontario, division Infrastructure and Transportation, is not using precast concrete bridge barriers since a long time for the same reason than Alberta is. The last time precast concrete bridge barriers were used was 1991. In that project, two different anchor types were used. Detailed information about the barriers and their anchors are presented in chapter 7.2.1 Anchorage details McKenzie Creek – Hwy 6, used by the Ministry of Transportation Ontario (MTO) 1991. Detailed drawings of the McKenzie bridge can be found in Appendix C. The Ministry of Transportation of Manitoba, of New Brunswick, and of Newfoundland and Labrador never used precast concrete bridge barriers. They normally use cast-in barriers on bridges, mainly F-shapes.

7.2.1 Ancho rage details McKenzie Creek – Hwy 6, used by t he Mini str y of Transportation Ontario (MTO) 1991 The compressive strength of the parapet should exceed a minimum of 30 MPa at 28 days and the cover of the reinforcing steel should have a minimum cover of 53±3 mm except as noted different. In addition, the anchorage assembly should be galvanized after fabrication, in accordance with CSA G164-M. The reinforcing bars should be in accordance with CSA Standard G30.16-M77 Grade 400W. Steel plates should conform to CSA Standard CAN3-40.21-M87 Grade 350W and sheaths for anchor ducts should be bright steel, rigid, corrugated type, 50 mm in diameter or equivalent, and approved by the MTO. The length of the parapet is 5940 mm and the height is 1120 mm.


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Two different anchor types are used with this parapet. The following figures present a cut through the barrier, the left one presenting the reinforcement and the right one showing the anchor:

Figure 40 – Cut through barrier, anchor type 1, used by the Ministry of Transportation, Ontario

Figure 41 – Cut through barrier, anchor type 2, used by the Ministry of Transportation, Ontario


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The deck construction is a precast concrete deck penal. Details of the anchors, fastening the barrier to the deck, are shown in the next figure. The panel anchorage assemblies, either type 1 or 2, are build every 220 mm into the barrier. This results in ... anchors per barrier.

Figure 42 – Anchor details: type 1 and type 2, used by the Ministry of Transportation, Ontario

The construction sequence consists of seven steps and the following should be applied: The backer rod should be a closed cell polyethylene type with a diameter of 1.5 times the joint width. And the joint sealant should be dow corning 888 silicone type. The finished thickness of the joint sealant should be 0.5 times the actual joint width. The used grout should be an approved non-shrink and non-staining type in accordance with designated sources for materials listing DSM 9.10.35. The epoxy resin should be Hilti C100-HIT and the bolt anchor should be compound with SUP-R-RESIN 392T or Solibond HR 200. Besides that the end faces and anchorage recesses of all panels should be abrasive blast cleaned prior to units being installed on deck. And end faces of adjacent panels should be wetted prior to grouting of joints. The Dywidag bar, nut and washer should be galvanized in accordance with CSA G164-M. The seven steps of the construction are the following: In the first step the precast concrete bridge barriers have to be set onto grout pad at correct alignment and spacing. Then, in the second step, a 25 mm diameter whole has to be drilled 250 mm long into the deck and wing barriers at first and last anchorage location. The wholes have to be brushed clean and blown out. Before any epoxy is used in the next step, the wholes have to be dry. In step three, the epoxy resin has to be placed into the drilled wholes and the 19.6 mm diameter Dywidag thread bars, Grade 60, have to be placed. The epoxy resin should reach a strength of precast concrete barriers in British Columbia.doc

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30 MPa. And during the setting of the epoxy the dowels should maintain in position and the loss of epoxy from the wholes should be prevented.

Figure 43 – Step I to III of the construction sequence of the McKenzie Creek Barrier, used by the Ministry of Transportation, Ontario

In step four the nuts have to be installed and tightened to snug fit with manual wrench. The grout should reach a strength of 30 MPa. The fist steps have to be repeated for remaining intermediate anchorage locations. After that all anchors should be tighten to snug fit. In step five the concrete surface at each panel joint should be wet. The backer rod should be installed on front and back face of joint between adjacent concrete panels. The joint should be filled with non-shrink grout up to 60 mm from top of panel units. In the next step, step six, the backer rod should be installed across the top of the joint between adjacent concrete panels. Silicone joint sealant should be applied along the full length of the dry joint against the backer rod, but stop silicone bread 25 mm from bottom of back face of barrier units. In the last step, step seven, the anchorage recesses should be filled with non-shrink grout flush with front face of barrier.


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Figure 44 – Step IV and VII of the construction sequence of the McKenzie Creek Barrier, used by the Ministry of Transportation, Ontario

7.3 United States of America anchor age details The only precast concrete bridge barrier, used in the United States of America, that I could find is the L.B. Foster Precast NJ-Shape which is a bolted-down barrier. This barrier is utilized in California was full-scale crash tested for Performance Level 2 in 1988. The height of the barrier is 34 inches (864 mm), consisting of a 10-inch (254 mm) high middle incline surface with a 55 degrees angle and a 21-inch (533 mm) high upper surface with a 84 degrees angle. The base width is 19 inches (483mm) and the top width is 9¾ inches (248 mm). The length of the barrier ranges from 12 feet (3658 mm) to 20 feet (6096 mm) in 2-feet increments. Since the barrier is developed a long time ago and not used very often the drawings are handmade and not really clear. Nevertheless, a cut through the barrier is shown in the following figure.


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Figure 45 – Section through L.B. Foster N J-Shape barrier, from Bridge Rail Guide 2005, FHWA

All reinforcing bars should be epoxy coated and the concrete should have a strength of 5000 psi (34.5 MPa). Anchors, bolts, washers, and nuts should be galvanized after fabrication, before installation. And the whole in the barrier should be filled with the same material used to grout the bolt in the barrier. The bolt that is used is a 1-inch diameter by 15½-inch (394 mm) HS Hot Dipped galvanized Kelibond Anchors set in Keligrout to a depth of 6½ inches (165 mm). After 24 hours after installation, the nuts should be torque to 700 foot-pounds (950 Nm), producing approximately 36,000 pounds (160 kN) of pre-tensioning in each bolt. The actual strength of each bolt, based on pull-out tests, was approximately 40,000 pounds (178 kN). A detail of the bolts is shown in the beneath figure.


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Figure 46 – Bolt detail of the L.B. Foster NJ-Shape barrier, from Bridge Rail Guide 2005, FHWA

The first anchor is 1 feet (305 mm) away from the edge of the barrier on both sides. The following anchors are every 2 feet (610 mm). That means that a 20 feet long barrier consists of ten anchors whereas the short barrier (12 feet long) consists of six anchors. Barriers, that have a length of 12 ft (3658 mm) up to 16 ft (4877 mm), need a connection plate to reassure the Performance Level. The steel plate which has a size of 0.6 x 6 x 24 inches (1.5 x 15 x 610 mm) and is galvanized. A detail drawing of the connection is shown in the beneath figure.


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Figure 47 – Barrier end detail of the L.B. Foster NJ-Shape barrier, from Bridge Rail Guide 2005, FHWA

7.4 Comparison of the anchor age details The aforementioned barrier from the Ministry of Transportation of Ontario (MTO) and the one from the United States of America are used for a comparison to the anchors used by the Ministry of Transportation in British Columbia. The table in Appendix D gives a summary of the important facts of the barriers and their anchors explained in the aforementioned sections. Before any comparisons are done it should be mentioned that two barrier types are definitely not enough to get reasonable results. Unfortunately, precast concrete bridge barriers are not used really often, mainly due to corrosion problems. Therefore more than these two precast concrete bridge barriers could not be find. Hence the comparison is done with only these two barrier types but the results should be used with caution.


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7.4.1 Comparis on of the BC MoT bolt-dow n precast co ncr ete bri dge barriers with the McKenzie precast brid ge barrier The length of the McKenzie precast bridge barrier (5940 mm) is longer than the ones used in British Columbia (vary between 1988 and 3980 mm). In addition, the McKenzie precast bridge barrier is with a height of 1120 mm higher than the barriers used in BC which have heights of 810 mm, 865 mm, and 875 mm. And the McKenzie bridge barrier has anchors every 220 mm which is a very short distance. Most precast barriers used by the Ministry of Transportation of British Columbia have a distance which varies between 450 and 700 mm. Due to this short distance the amount of anchors results in 26 compared to 4 or up to 7 (depending on the barrier type) for the precast barriers used in BC. The connection between precast bridge barrier is the hook and eye connection for both, the McKenzie and the ones used in British Columbia. The bolts of the McKenzie barrier which are used to fasten the barrier to the deck are, with a diameter of 19 mm, smaller than the one used by the Ministry of Transportation in British Columbia (24 or 25 mm). All bolts should be galvanized after fabrication. Due to the high amount of anchors the placing and fastening of the McKenzie barriers take longer than the barriers used in British Columbia. And the higher amount of anchors can be explained due to smaller bolts which result in less strength per bolt and a higher and longer barrier. Since so many factors are different a final conclusion is not possible. The anchor capacities as well as the necessary resistances should be analysed to be able for a final conclusion.

7.4.2 Comparis on of the BC MoT bolt-dow n precast co ncr ete bri dge barriers with the L.B. Foster NJ-Shape precast brid ge railing The L.B. Foster NJ-Shape precast bolt-down barrier can vary in the length from 3658 mm (12 feet) up to 6096 mm (20 feet). The short barrier length is comparable to the barriers used by the Ministry of Transportation in British Columbia (between 1988 and 3980 mm). The height of the barrier (864 mm) is, besides the unit differences, comparable to the 865 mm high barrier used in British Columbia. The number of anchors of the L.B. Foster NJ-Shape precast bolt-down barrier is with 6 anchors for the short barrier type also comparable to the BC ones (between 4 to 7 anchors). The long barrier with up to 10 anchors per barrier is not comparable to the anchors used in the barriers of British Columbia. The connection between adjacent barriers is different. The L.B. Foster NJ-Shape precast boltdown barrier uses a steel plate for short barrier types, between 12 and 16 feet long. The long barriers do not need a connection due to their heavy weight. Whereas the Ministry of transportation in BC uses the hook and eye conncetion.


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The anchor of the L.B. Foster NJ-Shape precast bolt-down barrier used to fasten the barrier to the deck has a diameter of 1 inch (25.4 mm) which is the same diameter of the anchor used by the Ministry of Transportation of British Columbia. The length of the anchor bolt is with 15½-inch (394 mm) slightly shorter than the one used in British Columbia (400 up to 490 mm). Finally it can be said that this precast bolt-down barrier with a short length is very similar compared to the precast bolt-down barriers used in British Columbia. The only difference is the connection between adjacent barriers, especially for the short ones. If this connection difference makes any important differences for crash test capabilities cannot be said at the moment. Nevertheless this barrier was crash tested in November 1988 and accepted by the Federal Highway Administration, US. Department of Transportation as a Performance Level 2 (Testing Level 4) barrier in March 1989.


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8.


Review the effect of typ e of bri dge (concr ete slab vs. box gi rder) on the anchorage capacity

The five standard bolt-down systems used by the British Columbia Ministry of Transportation are the following:

NAME

Number

Type of superstructure box girder (16m long) box girder (18 m long)

Used precast parapet [height ]

1

Standard Precast Concrete Bridge

2965

2

Elkins Bridge

7780

3

Misinchinka Bridge

6819

concrete slab

865 mm

4

Hudgens Bridge

7476

concrete Slab

875 mm

5

Twan Creek Bridge

8023

concrete slab

810 mm

865 mm 865 mm

Table 7 – Standard precast concrete bolt-down systems used by the BC MoT

The bolt-down precast concrete bridge barrier that was used by the Ministry of Transportation in Ontario is the following:

NAME

6

McKenzie Creek – Hwy 6

Number

Type of superstructure


-

Concrete slab

1120 mm

Table 8 – Precast concrete bolt-down system used by the MoT Ontario

The bolt-down precast concrete bridge barrier that was used by the Department of Transportation of the United States is the following:

NAME

7

L.B. Foster NJ -Shape

Number

Type of superstructure


-

Concrete slab

34 inch (864 mm)

Table 9 – Precast concrete bolt-down systems used by the US. DoT, FHWA

Unfortunately, I could not get any information about the superstructure of the McKenzie Creek Bridge. And I could also not find out if the L.B. Foster NJ-Shape barrier was used on a bridge, as well as where and when. Therefore, the superstructures as well as the connection between the barrier and the superstructure of the BC MoT bridges are explained and the anchor capacities are determined in the following subchapters. The aforementioned summary in Appendix D: Summary of important factors for the comparison of different types of anchors,


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barriers and their superstructures…………………………………… might be helpful here as well. The resistance of an anchor should be determined on the basis of seven possible failure modes which are shown in the figure on the next page as well as listed here: ¾

Tension capacity, taken as the lesser of: • Steel strength of anchor in tension; or • Concrete breakout resistance in tension; or • Pullout resistance of anchor in tension; or • Concrete side face blowout resistance in tension;

¾

Shear capacity, taken as the lesser of: • Steel strength of anchor in shear; or • Concrete breakout resistance of anchor in shear; or • Concrete pryout resistance of anchor in shear.

Figure 48 – Failure modes for anchors under tension and shear load, from CSA A23.3-04, Figure D.1 and D.2

The calculated anchor capacities are based on the information that was given to me by the BC MoT. Since I did not have all details I determined only those capacities for which I had the necessary information. precast concrete barriers in British Columbia.doc

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8.1 The anchor capacity of barri ers anchor ed to concrete slabs 8.1.1 The Misinchinka Br idg e, # 6819 The Misinchinka bridge is built with the 865 mm high precast concrete bridge barrier consisting of two different versions, P1 and P2. The length of the P1 parapet is 2194 mm and 1988 mm for P2. The estimated mess for the parapet is 1,500 kg each for P1 and 1,300 kg each for P2. The Misinchinka bridge precast concrete parapet is used in combination with a precast concrete deck panel superstructure with a compressive strength of 35 MPa after 28 days. More details about the precast concrete deck panels can be found in drawing 6819-10 of the BC MoT in Appendix B. The blockout is every 423 mm for the P1 model and every 496 mm for the model P2 R which results in five anchors per barrier. The plan and elevation view of Parapet MK PA1 is shown in the beneath picture.

Figure 49 – Plan and elevation view of the Misinchinka Bridge, from drawing 6819-9, BC MoT

Parapet anchor inserts, also described in the figure below, are set in the exterior concrete deck panels 260 mm away from the edge of the panel. The anchor inserts consist of a


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burrard coupler for a M24 bolt which is 245 mm long. The size of the burrard coupler plate is 200 mm x 50 mm x 10 mm.

Figure 50 – Parapet anchor insert of the Misinchinka Bridge, from drawing 6819-8, BC MoT

Once the anchor bolt is fixed, the bolt sleeve has to be filled with non shrink grout with a compressive strength of 50 MPa after 28 days as shown in the following figure.

Figure 51 – Misinchinka Bridge after the installation of the anchor bolt, from drawing 6819-10, BC MoT


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8.1.1.1 The anchor capacity of the Misinchinka Bridge The tension force of the burrard coupler is: 69 kN. The shear resistance of the bolt sleeve is: 25mm Vr,BS = 50MPa* 2π *190mm = 746 kN 2

8.1.2 The Hudg ens B ridge, # 7476 The Hudgens bridge is combined with the 875 mm high precast concrete bridge barrier consisting of two different versions, P1 and P2. The estimated mess for the Hudgens bridge barrier is 1,394 kg each for P1 and 1,557 kg each for P2. And the length of the P1 barrier is 2185 mm and for P2 it is 2442 mm. The Hudgens precast concrete bridge barrier is used in combination with a concrete deck panel superstructure a compressive strength of 35 MPa after 28 days. More details about the concrete deck panels can be found in drawing 7476-11 of the BC MoT in Appendix B. The blockout is every 548 / 547 mm for the P1 and P2 model which results in four R anchors per barrier. The plan and elevation view of Parapet MK P2 is shown in the picture beneath.


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Figure 52 – Plan and elevation view of the Hudgens bridge, from drawing 7476-12, BC MoT

The exterior bridge deck panel is having a burrard coupler set 50 mm deep into the concrete. A detail of the bridge deck where the barrier is placed can be seen in the following figure.

Figure 53 – Section through exterior bridge deck, from drawing 7476-12, BC MoT

Figure 54 – Detail drawing of the nut in the panel deck, from drawing 7476-12, BC MoT

Once the anchor bolt is fixed, the bolt sleeve can be filled with non shrink grout with a compressive strength of 50 MPa after 28 days as it can be seen in the following figure.


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Figure 55 – The Hudgens precast concrete bridge barrier # 7476 after the installation of the anchor bolt, from drawing 7476-12, BC MoT

8.1.2.1 The anchor capacity of the Hudgens Bridge The tension force of the burrard coupler is 69 kN. The shear resistance of the bolt in the superstructure is: Vr,Bolt = 35MPa* 2π

27mm 2

*50mm = 148 kN

The shear resistance of the bolt sleeve is: Vr,BS = 50MPa* 2π

25mm 2

*190mm = 746 kN

8.1.3 The Twan Creek Bridge, # 8023 The Twan Creek bridge is build in combination with the 810 mm high precast concrete bridge barrier consisting of two different versions, P1 and P2. The length of the parapet is 3038 mm for P1 and 3043 mm for P2. The Twan Creek bridge precast concrete parapet is used in combination with a concrete precast deck superstructure with a compressive strength of 35 MPa. More details about the concrete precast deck can be found in drawing 8023-20 of the BC MoT in Appendix C. The concrete precast bridge deck is having a blockout every 762 mm. The blockout is a 50 mm diameter and 209 mm long PVC tube. A detail drawing of the bridge deck can be seen in the picture below. Due to the anchor distance of 762 mm, 4 anchors are placed into one barrier.

Figure 56 – Detail of the precast concrete deck bridge, from drawing 8023-21, BC MoT

Once the anchor bolt is fixed, the bolt sleeve can be filled with non shrink grout of a compressive strength of 50 MPa after 28 days. After that the blockout can be filled with the same grout as well.


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Figure 57 – Parapet connection to deck at Twin Creek bridge, from drawing 8023-22, BC MoT

8.1.3.1 The anchor capacity of the Twan Creek Bridge The shear resistance of the bolt sleeve is: Vr,BS = 50MPa* 2π

25mm 2

* (135 + 200)mm = 1315 kN

8.2 The anchor capacity of barriers ancho red to box gir der flange 8.2.1 The Standard Precast Con crete Bridge, # 2965 The Standard precast concrete bridge is combined with the 865 mm high precast concrete bridge barrier consisting of six different versions, P1, P2, P3, P4, P5, and P6. The length of the parapet is 2980 mm for P1, P2, and P3 and 3980 mm for P4, P5, and P6. The estimated mess for the parapet is 1,900 kg each for P1, P2, and P3 and 2,550 kg each for P4, P5, and P6. This standard concrete precast parapet is used in combination with a twin cell concrete box stringer superstructure 700/16/E or I. More details about the twin cell concrete box stringers can be found in drawing 2965-23 of the BC MoT in Appendix B. There are five anchors in the P1, P2, and P3 model and seven in the P4, P5, and P6 models. Hence, the anchor construction is every 580 mm for the P1, P2, and P3 model and every 620 mm for the models P4, P5, and P6. The plan and elevation view of Parapet MK P1 is shown in the figure on the next page.


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Figure 58 – Plan and elevation view of the standard precast parapet MK P1, from drawing 2965-4, BC MoT

The exterior box stringer has a 100 mm diameter whole for the anchor. A section through the exterior stringer can be seen in the beneath picture.

Figure 59 – Section through exterior stringer MK 700/16/E, from drawing 2965-23, BC MoT precast concrete barriers in British Columbia.doc

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Once the anchor bolt is fixed, the bolt sleeve can be filled with non shrink grout with a compressive strength of 50 MPa after 28 days (see Figure below).

Figure 60 – Standard precast concrete bridge after installation of the anchor bolt, from dwg. 2965-6, BC MoT

8.2.1.1 The anchor capacity of the Standard Precast Concrete Bridge The shear resistance of the bolt sleeve is: Vr,BS = 50MPa* 2π

25mm 2

* (190)mm = 746 kN

8.2.2 The Elkin s Br idge Precast Concrete Parapets, #7780 The parapet which is used at Elkins bridge is the same than described in 8.2.1 The Standard Precast Concrete Bridge, # 2965. The only difference is the superstructure which is in this case the stringer MK 700/18/E or I. This twin box is 2m longer than the one used in chapter 8.2.1 The Standard Precast Concrete Bridge, # 2965. More details about the concrete deck panels can be found in drawing 7780-4,6 of the BC MoT in Appendix B. The exterior box stringer is having a whole to put the anchor bolt through. A section through the exterior stringer can be seen in Figure 59 – Section through exterior stringer MK 700/16/E, from drawing 2965-23, BC MoT. Another difference is the filling of the bolt sleeve and the blockout (see drawing beneath). This time the bolt sleeve is filled with non shrink grout which should have a compressive strength of 35 MPa after 28 days. Besides that, the blockout is also filled with non shrink grout with a compressive strength of 35 MPa after 28 days. precast concrete barriers in British Columbia.doc

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Figure 61 – Elkins bridge after the installation of the anchor bolt, from drawing 7780-6, BC MoT

8.2.1.1 The anchor capacity of Elkins Bridge The shear resistance of the bolt sleeve is: Vr,BS = 35MPa* 2π

25mm 2

* (190)mm = 522 kN


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9.


Carry out site visi ts to exist ing brid ges to see the exist ing B C MoT precast c oncr ete bolt down barrier system in service

There exist many bridges with bolt-down precast concrete barriers around Vancouver built by the Ministry of Transportation of British Columbia. One of the closest bridges is the Birkenhead Causeway Bridge No. 8024 situated just behind Pemperton. This bridge uses a barrier similar to one described before in combination with a twin cell box stringer, 700/18/E or I, superstructure.

9.1 Detailed info rmation of the con stru ctio n of the Birk enhead Causeway B ridge No. 8024 The barrier that is used together with the Birkenhead Causeway Bridge has a height of 900 mm with a compressive concrete strength of 50 MPa at 28 days. The reinforcing steel should be in accordance with CSA Specification G30.18M, Grade 400R. And the reinforcing cover should be at least 60 mm unless noted otherwise. A section through the barrier is shown in the beneath figure. The bolt sleeve, the blockout, as well as the bolt itself are the same as described before in chapter 7.1.2 The 865 mm high precast concrete bridge parapet.

Figure 62 – Section through the Birkenhead Causeway Bridge barrier, from dwg. 8024-9, BC MoT precast concrete barriers in British Columbia.doc

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Four different barrier types are used: P1, P2, P3, and P4. The barrier itself has a length of 2980 mm for the P1, P2, and P3 model and 3980 mm for the P4 model. The estimated mass is 2000 kg for the P1, P2, and P3 model and 2700 kg for the P4 model. Barrier type P1, P2, and P3 has five anchors per barrier with an spacing of 620 mm and an edge distance of 250 mm. And barrier type P4 has seven anchors per barrier with a spacing of 580 mm and an edge spacing of 250 mm.

Figure 63 – Plan and elevation view of the Birkenhead C auseway Bridge barrier, from dwg. 8024-9, BC MoT

A cut through an interior box stringer, showing the anchor bolt, is shown in the following figure.

Figure 64 – Cut through box stringer of the B irkenhead Causeway Bridge, from dwg. 8024-9, BC MoT precast concrete barriers in British Columbia.doc

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Figure 65 – After placing the Birkenhead Causeway Bridge barrier, from dwg. 8024-9, BC MoT

9.2 Site visit : Bir kenhead Causeway Bridge No. 8024 Unfortunately, it snowed heavy the night before I visited the bridge. But I dug out parts of the barriers and took some pictures.

Figure 66 – Birkenhead Causeway Bridge, traffic and pedestrian barrier precast concrete barriers in British Columbia.doc

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Figure 67 – Birkenhead Causeway Bridge, view on traffic with the pedestrian barrier in the back

Figure 68 – Birkenhead Causeway Bridge, view from the top on the traffic and pedestrian barrier


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Figure 69 – Birkenhead Causeway Bridge, view the back of the traffic barrier

Figure 70 – Birkenhead Causeway Bridge precast concrete barriers in British Columbia.doc

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10.

Precast concrete barrier fabric ation plants in British Columbia

The Ministry of Transportation in British Columbia published with Section 941 of the Standard Specifications for Highway Construction 2006 all necessary information to fabricate precast reinforced concrete barriers. Within British Columbia, there are nine factories which produce precast concrete bridge barriers in accordance with the BC MoT's Standard Specifications for Highway Construction 2006. These nine factories are listed in the following table:

Fabri cator

City

Webpage

1 C Grosso Pre-Cast Ltd.

Williams Lake

http://www.grossoprecast.com/

2 Diversified Concrete Products

Prince George

http://www.scoutenengineering.com

3 Eagle West Truck & Crane Inc.

Abbotsford

http://www.eaglewestcranes.com

4 Kemp Concrete Products

Kamloops

http://kempconcrete.com

5 Kon Kast Products

Kelowna

http://konkast.com

6 Skeena Concrete Products Ltd.

Terrace

7 Surespan Structure Ltd. Tri - B Concrete Building 8 Supplies Ltd. 9 Tri-Kon Precast Products Ltd.

Duncan

http://www.surespanstructures.com

Lillooet Cranbrook

http://www.trikonprecast.com

Table 10 – List of fabricators of precast concrete bridge barriers within British Columbia

Since the fabrication of Eagle West Truck & Crane Inc. is the closest one to Vancouver I st asked for an appointment and finally went on a plant visit on December 1 2006. Hence all the following pictures and comments are from this one company. The daily amount of barriers that are produced is at the moment (in December) about sixty. But the maximum possible production amount per day is hundred and twenty. This amount is double compared to the amount they produce at the moment. This difference is a result of seasonal changes. Four people are working at the plant which shows that not a lot man work is necessary for the production of precast concrete barriers. The plant has a daily procedure which is the following: Precast concrete barrier forms get prepared for poring in the morning. After the reinforcement and the anchors are placed and fixed, the concrete which is prepared as defined in the Standard Specifications for Highway Construction 2006 is pored and vibrated. In Figure 71 – Filled precast concrete barrier forms at the plant of Eagle West Truck & Crane, with two barriers next to each other, can be seen. And in Figure 72 – Hook bars used for the connection of adjacent barriers at the plant of Eagle West Truck & Crane and Figure 73 – Eye bar(s) used for the connection of adjacent barriers at the plant of Eagle West Truck & Crane are shown. precast concrete barriers in British Columbia.doc

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Figure 71 – Filled precast concrete barrier forms at the plant of Eagle West Truck & C rane

Figure 72 – Hook bars used for the connection of adjacent barriers at the plant of Eagle West Truck & Crane


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Figure 73 – Eye bar(s) used for the connection of adjacent barriers at the plant of Eagle West Truck & Crane

After the barriers are pored, they will lay down for twenty-two hours before they are taken out of the concrete form and put aside, where they will rest to develop the necessary strength within the next 28 days. Due to the winter conditions the fresh concrete, in the forms and after that on the side, are kept warm so that the chemical reaction of the cementing material can take place and get the necessary strength. The concrete forms will get cleaned that they can be used again.

Figure 74 – Precast concrete barriers after 3 days at the plant of Eagle West Truck & Crane

The precast concrete bridge barriers that are produced at Eagle West Truck & Crane Inc. are bridge transition barriers which are used in the transition between the bridge and the road before. Here are four pictures showing the anchor in the bridge barrier transition:


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Figure 75 – Side and end view of a precast concrete bridge barrier at the plant of Eagle West Truck & Crane

Figure 76 – Side and end view of the precast concrete bridge barrier anchor at Eagle West Truck & Crane

The placing time of the barriers vary depending on the type of barrier and placing method. But in average it can be said that it takes about 10 minutes per barrier which results in six barriers per hour. Eagle West Truck & Crane uses a clamp to put the barrier in place and not the special prepared wholes. This method is faster and easier than the old one. And the risk of damaging a barrier while placing is not much higher than with the old method.


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Conclusions A literature review on bridge barriers as well as an overview of precast concrete reinforced bridge barriers that are used in British Columbia in Canada has been given and existing barrier types have been presented. Important issues in the design of bolt-down precast concrete reinforced bridge barriers have been demonstrated and discussed. Codes change and it is difficult to stay up to date. The decision of the Ministry of Transportation of British Columbia to design the barriers once again with the new design requirements is in matter of safety very important. Although the literature review in this report is based on the Canadian Highway Bridge Design Code CAN/CSA-S6-00 published in 2000, the changes to the new 2006 Edition of the Canadian Highway Bridge Design Code which is published at the moment should be reviewed in one of the next research projects. Since this research is the first one of a series of research reports, which gives an introduction into the topic precast concrete reinforced bridge barriers with an emphasis on boltdown barriers, the work on this research topic can still be continued. The first chapters of this research giving a literature review are finished topics, but the chapters afterwards which include the comparisons are chapters that should be continued in the next research project. It was difficult to get the necessary information from other jurisdictions than British Columbia in that short period in which this report was produced. Most jurisdictions in North America were helpful and replied quickly to my questions but there are still open information requests. The biggest problem was that precast concrete bridge barriers are not common and therefore it was difficult to find comparable barriers. Thus the search for precast concrete bridge barriers was widen to alternative jurisdictions, mainly to Europe. Finally, it can be said that more investigation, especially into the two barriers which were used for the comparisons and into finding more comparable barriers, should be done.


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References [1]

Barker, R. M. and Puckett, J. A. , 1997, Design of Highway Bridges: Based on AASHTO LRFD, Bridge Design Specifications, John Wiley and Sons, Inc., New York

[2]

Bridge Design Manual (BDM), 2006, Washington State Department of Transportation, www.wsdot.wa.gov/fasc/EngineeringPublications/BDMManual/BDMAugust2006.pdf, th 16 Nov. 2006

[3]

Bridge Design Specifications, American Association of Highway and Transportation nd Officials (AASHTO), 1997, 2 Edition Washington D.C.

[4]

Bridge Design Specifications, American Association of Highway and Transportation rd Officials (AASHTO), 2004, 3 Edition, Washington D.C.

[5]

Bridge Rail Guide, 2005, U. S. Department of Transportation, Federal Highway th Administration (FHWA), http://www.fhwa.dot.gov/bridge/bridgerail/, 16 Nov. 2006

[6]

Canadian Highway Bridge Design Code (CHBDC) – CAN/CSA-S6-00, December 2000, CSA International

[7]

Canadian Highway Bridge Design Code (CHBDC) – CAN/CSA-S6-88, June 1988, CSA International

[8]

Concrete Design Handbook, 3 Edition, January 2006, Cement Association of Canada, Ottawa, Ontario, Canada

[9]

Commentary to the Canadian Highway Bridge Design Code – CAN/CSA-S6-00, December 2000, CSA International

rd

[10] Commentary to the Ontario Highway Bridge Design Code – OHBDC-91-01, rd 3 Edition, 1992, Ontario Ministry of Transportation, Downsview, Ontario th

[11] Handbook of Steel Construction, December 2005, 8 Edition, third printing, Canadian Institute of Steel Construction, Toronto, Ontario, Canada [12] McDevitt, C. F., Basics of Concrete Barriers, U. S. Department of Transportation, Federal Highway Administration, http://www.tfhrc.gov/pubrds/marapr00/concrete.htm, th 29 Nov. 2006 rd

[13] Ontario Highway Bridge Design Code – OHBDC-91-01, 3 Edition, 1992, Ontario Ministry of Transportation, Downsview, Ontario


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[14] Ross, H. E., D. L. Sicking, R. A. Zimmer, and J. D. Michie, 1993, Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features, TRB, National Cooperative Highway Research Program (NCHRP), National Research Council, Washington D.C. [15] Standard Specifications for Highway Construction, 2006, Section 941: Precast Reinforced Concrete Barriers, British Columbia Ministry of Transportation (BC MoT), Victoria [16] Supplement to the Canadian Highway Bridge Design Code - CAN/CSA-S6-00, June 2006, CSA International [17] Wong, J., August 2005, Analysis Method for the Design of Reinforced Concrete Bridge Barrier and Cantilever Deck under Railing Loads as Specified in CAN/CSA-S6-00 (CHBDC), Master Thesis, University of British Columbia, Vancouver


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Appendix Appendix A:

Standard Drawings of the Standard Specifications for Highway Construction, 2006, Section 941, published by the British Columbia Ministry of Transportation (BC MoT)……………………………………………… 84

Appendix B:

Drawings of the standard precast concrete parapets and transitions of the British Columbia Ministry of Transportation (BC MoT)………………………… 113

Appendix C:

Drawings of the McKenzie precast concrete bridge of the Ministry of Transportation of Ontario (MTO)…… 127

Appendix D:

Summary of important factors for the comparison of different types of anchors, barriers and their superstructures……………………………………. 131


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App endix A : Standard Drawings of the Standard Specifications for Highway Construction, 2006, Section 941, published by the British Columbia Ministr y of Transpor tation (BC MoT)


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App endix B : Drawings of the standard precast concrete parapets and transitions of the Briti sh Columb ia Minis try of Transpor tation (BC MoT)


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App endix C: Drawings of the McKenzie precast concrete bridge of the Ministry of Transportatio n of Ontario ( MTO)


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App endix D: Summary of important facts for the comparison of di fferent types of anchors, barriers and their superstructu res

Barrier type

1

2

3

t s e a g c d e i r r 5 P B 6 e 9 d t r e 2 a r # d c n n a o t S C

e g d i r B 9 a 1 k 8 n 6 i h # c n i s i M

e g d i r 6 B 7 s 4 n 7 e # g d u H

P1, P2, P3

P4, P5, P6

BC MoT

from

P1

P2

BC MoT

P1

P2

BC MoT

barrier length [mm]

2980

3980

2194

1988

2185

2442

weight/barrier [kg]

1900

2550

1500

1300

1394

1557

865

barrier height [mm]

865

number of anchors per 5 @ 620 7 @ 580 5 @ 423 4 @ 496 barrier [mm] compressive strength of the barrier concrete

875 4 @ 548

50 MPa

50 MPa

50 MPa

type of superstructure

Twin Cell Box Stringer 700/16/E or I

Precast Concrete Deck Panel (f c' =35 MPa)


connection type between adjacent barriers

hook and eye

hook and eye

hook and eye

-

-

-

permanent

permanent

permanent

Tested PL/TL Period of us age

25 mm diameter, M24 bolt, 400 mm 490 mm long bolt, long, c/w 10x80x80 Description of anchor c/w nuts, thread two mm washer ends (70 mm) (galvanized) precast concrete barriers in British Columbia.doc

25 mm burrard coupler with a M24 bolt galvanized c/w washer page 131 of 142

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4

5 3 k 2 e 0 e 8 r # C n e a g d w i T r B

e g d i 0 r 8 B 7 7 s n # i k l E

Barrier type

P1, P2

P3

P1

BC MoT

from

P2

BC MoT

barrier length [mm]

2980

3980

3038

3043

weight/barrier [kg]

1900

2550

-

-

865

barrier height [mm]

number of anchors per 5 @ 620 7 @ 580 barrier [mm] compressive strength of the barrier concrete

810

4 @ 762

50 MPa

50 MPa

type of superstructure

Twin Cell Box Stringer 700/18/E or I


connection type between adjacent barriers

hook and eye

hook and eye

-

-

permanent

permanent

Tested PL/TL Period of us age

25 mm diameter, 490 mm long, c/w Description of anchor nuts, thread two ends (70 mm)


25 mm diameter, 470 mm long, galvanized A307, threaded two ends, c/w double nuts one end

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6 t s e a g c d e i r r P B e e t i z e n r e c K n c o C M

Barrier type

7 , r e i n r r r w e t a o s b o d F e d p . a e t B . h l o L S - b J N

MoT Ontario

USA, California

barrier length [mm]

5940

12 feet (3658 mm) - 20 feet (6096 mm) in L/8inch increments

weight/barrier [kg]

-

-

barrier height [mm]

1120

34 inches (864 mm)

26 @ 220

12 ft: 6 @ 610 mm 20 ft: 10 @ 610 mm

30 MPa

34.5 MPa (5000 psi)

Precast Concrete Deck Panel

Cement Concrete Pavement

hook and eye

steel plate

Tested PL / TL

PL-2

TL-4 =PL-2

Period of us age

permanent

permanent

from

number of anchors per barrier [mm] compressive strength of the barrier concrete type of superstructure connection type between adjacent barriers

1-inch (25.4 mm) diameter by 15½-inch 19.6 mm diameter (394 mm) HS Hot Dipped galvanized Kelibond Description of anchor Dywidag thread bars, Grade 60 Anchors set in Keligrout to a depth of 6½ inches (165 mm)


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