Bridge Design

FOR INTERNAL USE ONLY

Cawangan Jalan, Ibu Pejabat JKR, K.L

BUKU PANDUAN REKABENTUK JAMBATAN

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CONTENTS

Chapter 6 - PIER

.Preface. Chapter-1STANDARD JKR PRACTICES IN BRIDGE DESIGN

Design Consideration-Pier ComponentsLoadingPile Layout and StabilityDesign of Pier Base and Stem-Detailing Chapter 7 - ABUTMENT

Organisation Objective-FunctionScope of Work. Standard Design Practices-Design ProcedureBridge Furnishings-Standard Prestressed Beams Chapter 2 - HYDROLOGY

20,

Factors Affecting Florid Runoff Flood History Rational Method-Unit Hydrograph Method-Regional Flood Frequency Method-Determination of the Flood Water Level and velocityComputation of Back Water CurvePresentation of Sketch Proposal . Chapter 3 - BRIDGE LOADING

65

Loads Acting On A Bridge Superstructure-Procedure For Determination Of Loads Chapter 4 - DECK SLAB

104

Pigeaud's Method-Westergaards Method-Application Chapter 5 - BEARING, DOWEL BARS, EXPANSION JOINTS 114 Bearing: Functions-TypesElastomeric BearingsProperties of Elastomer-Basic Assumptions in Design ' Dowel Bar: Design of Dowel Bar Expansion Joint: Functional RequirementsClassificationSelection of Joint TypeDesign Consideration-Design Load Anchorage System. InstallationProvision for DrainageMaintenance


146

168

Types of Abutment-Modes of FailureScouring Protection and DrainageDesign LoadingsCantilever Type Retaining Wall Abutment Counterfort Retaining wall-Joints in Retaining Wall Abutments-Abutment For The widening of Bridge. Chapter 8 - FOUNDATION

322

Part I: Design of Bridge Foundations .323 Shallow Foundations-Piled Foundations-Lateral Load Capacity of.Piles Analysis of Global Pile GroupUnc6rtainities of the Analytical Methods Good Design Practice _ Part II: Design of Piled Foundation 332 Classification-Common Types of Piles Used in JKR Projects-Selection of Pile Type-Design of Single Pile-Factor of Safety-Pile Bearing on Rock-pile Bearing capacity-Negative skin FrictionDesign of pile Group Chapter 9 - DESIGN CODES AND TRAFFIC LOADING FOR HIGHWAY BRIDGES 364 Current and Future Design StandardsLimit state Design-Standard Highway HA And HB Loadings-Secondary Highway Loading Appendices: Philosophy of Limit State DesignDefinitions of Some Bridge Terms-A.storical Development of BS 5400-Terms of Reference for the Design And Supervision of Bridges.

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Chapter 10 - WORKED EXAMPLE OF JAMBATAN DI ATAS SG. ALOR PASIR KELANTAN Data: Proforma, location plan, cross section of river at bridge site, general layout i - vi Hydrological Calculation Calc.Sheet 1 - 10 Loadings on Bridge Superstructure 11 - 20 Design of Rubber bearing and Dowel Bar 21 - 32 Design of Deck Slab 33 - 38 Pier 39 - 60 Abutment 61 - 92 EXAMPLE OF WORKING DRAWINGS APPENDIX 1-8 METRIC CONVERSATION TABLE SEKALUNG BUNGA 'Setinggi*-tinggi terima kasih dan penghargaan hendaklah dirakamkan'bagi mereka yang telah banyak menyumbang dan berusaha untuk menjayakan penerbitan Buku Panduan Rekabentuk Jambatan ini: Sebelum 1984 Ir. Omar bin Ibzafrim. Ir. Kassim Junid Ir. Hon Too Fang Ir. Dzulkifli b. Abdullah Ir.-Mariyam bt. Ismail Ir. Will'iam Tan Chee Keong Ir. Ng See King Ir. Abu Hanifah b. Abdullah Ir. Lim Cheng Hock Ir. Lee Chee Hai Ir. Yap Huat Hoe Ir. Yu Hain Teck Selepas 1984

Ir. Nasaruddin b.Meor Abu Bakar Ir. Rohani bt. Abd. Razak Ir. Mohd. Murshid b. Omar Ir. Dang Anom bt. Md. Zin Ir. Wan Abdul Aziz b.Hj. Ariffin Ir. Baharanuddin b. Che Zain Ir. Sabariah bt. Bachik Ir. Ng See King J Ir. Mohd. Hakim b. Mohd. Amin Ir. Dzulkifli'b. Abdullah Ir. Abdul Halim b. Marzuki Ir. Abu Bakar b. Mohd. Said Ir. Ku Mohd.Sani b.Ku Mohamad . Ir. Shamlan b. Hashim Ir. Lim Char Ching Ir. Md. Razali b. Hj. Yusak Ir. Othman b. Ibrahim Ir. Ahmeed Tarmizi b. Ramli Ir. Mohd. Hisham b.Mohd. Yassin Ir. Zainuddin b. Jasmani Ir. Shamsuddin b. Sabri. Ir. Mustaffa Kamal b. Abu Bakar Ir. Mohd. Zamri b. Shaari Ir. Sohaimi b. Mohd. Yassin Ir. Abd. Latif b. Mokhtar Ir. Tengku Hishamuddin b.Tengku Abdullah. Penyediaan Pelan-pelan Puan Salmah bt. Wahab Encik Kamaruzamau b. Osman. Encik Abdul Aziz b. Sabda Encik A. Kamal b. A. Rahim Encik Arshad Marzuni Encik Abd. Hadi b. Mohd. Sharif Encik Johari b. Yahya Encik Mohd. Nor b. Zainuddin Encik Ghazali b. Jantan Puan Siti Hafsah bt.Kusni Puan Hayati bt. Mohd. Nayan Puan Ooi Kooi Kee Encik Zainal Akmar b. Yaacob Puan Salasiah bt. Othman Puan Yeo Seok Kin Encik Zailan b. Jumani Encik Teoh Jit Liang Encik Omar b. Munam

Ir. Tham Kum Weng Cawangan Jalan, Ibu Pejabat JKR, K.L

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Jurutaip 3. To plan and implement projects of major bridges for federal roads. 4. To give technical advice to the JKR States/Projects/ Road brcmcK in the structural design of bridges, bridge construction activities and on the transportation of heavy vehicles on JKR bridges. 5. To plan and implement research program to improve the design construction and maintenance bridge in JKR. 6. To participate in training activities by giving lectures and talks in courses organised by the JKR Training Centre and other units/sections.

Puan Normah bt. Md. Noor Puan Ruhani bt. Hamat Puan Sally Wong Kakitangan-kakitangan Lain Yang Turut Sama Menjayakan Penyediaan Buku Panduan ini. Puan Rodiah bt.'Mat Saman Encik Abd.Hazim b. Ibrahim Encik Mohd. Aziz b. Shamsuddin Encik Onn b. Sulaiman Encik Tajuddin b. Hamzah Cik Endon bt.Mansor Encik Rosli b. Talib Encik Mat Yusof b. Hashim Puan Jaswir Kaur Puan Shaharah bt. M. Shariff Encik Ishaik b. Indon Puan Hawa bt. Mohd. Said Encik Md. Shamri b. Hj. Amin. CHAPTER

1.3 Scope of Work . The design works in the Bridge Section involve the preparation of design calculations, presentation ahd checking of working drawings, preparation of specification and bill of quantities. The time taken to fully complete a project will depend on the availability of the necessary imformation, plans, etc. forwarded to this section. The procedure in carrying out A. design project is shown in the flow chart of the Bridge . Design Section (Appendix I).

1

STANDARD JKR PRACTICES IN BRIDGE DESIGN 1. INTRODUCTION 1.l Organisation Objective To plan and improve the development of the infrastructure and public services in the transportation system such as bridges, fly overs & culverts for roads so that they will be safe, of high quality and economical so as to fulfill the country's social and economic development. 1.2 Function 1. To plan and design new structures or suggest remedial works for existing structures of river,bridges/flyovers/ foot bridges/culverts for federal, state and regional scheme roads. 2. To co-ordinate the design activities of bridge projects for federal roads designed by the Consulting Engineers. Cawangan Jalan, Ibu Pejabat JKR, K.L

2.

Standard Design Practices: 2.1 Types of Bridges The types of bridges designed by the Section are road bridges over high ways, railway line, river and some times pedestrian bridges. All bridges designed are of reinforced and pre stressed concrete based on the length of the standard beams available in the Section. See (Appendix II) Attempts are now underway to.design continuous box girder bridges.

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2.2 Design Codes The design of concrete bridges in the section has been based on British Standards such as the BS 153 Part 3A (loading), CP '114 (reinforced concrete) and CP 115 (prestressed concrete). In addition, technical memoranda pub lished by the British Department of Transport are also used. These memoranda. are essential reference material because firstly, they lay down principles of design for bridges based on their distinct features as compared to other structures and secondly, they keep abreast of current design recommendation based on research. The code of practice on Limit State Design (CP 110) is not applicable to design of bridges because it is not compatible to the loading requirements of BS 153 Part 3A. A new bridge design code incorporating the Limit State Design and various technical memoranda embodied in BS 5400 has been available since 1978. However, controversial parts of the code are still under review in Britain and not yet implemented in full. A list of design codes related to the design of bridges as practised by this section is shown in Appendix III. 11 It is a practice in the section that all road bridges are designed to HA loading and checked for 45 units of HB loading guided along the centre line of the carriageway. The procedure of computing the designed live loads and dead loads is dealt with in the chapter on loading. For a skew angle of less than 200, the beams can be used and if the skew angle is greater than 200, the beams should be analysed using the GRIDP/STRU analysis computer programme that is available in the computer section.


3. Design Procedure: 3.1 Proforma With reference to the flow chart in the implementation of the bridge designs, the proforma is very important to the designer to decide the arrangement of the bridge for the preparation of a sketch proposal .When there is a request to design a bridge from other sections, the proforma form will be sent to the particular section to fill in their requirements e.g. location, t9pe of road, services and longitudinal cross section of the river at a distance of 100 ft. upstream and 100 ft. downstream if it is over a river. Roads are classified by their JKR standard types (Appendix IV) The selection of the type of parapet for a bridge is of fundamental importance to its appearance.It is a practice in the section, to have either a solid concrete parapet or a steel railing (Appendix VI). Each can have visual merits depending on the general configuration of the bridge structure. In the case of a bridge over a highway, it would be appropriate to have.a steel railing so that the bridge deck will appear slender. For remote areas, since maintenance is difficult, the use of concrete parapet is preferable. 4.2 Services The service that are usually required by the client.to be placed on the bridge structure are watermains, telephone and electrical ducts. Brackets for the water main are provided in the form of 'J' or 'L' shape as in Appendix VI. The telephone and electrical ducts are usually placed in the concrete kerb and if there are more ducts, they are hung by the side of the beam.

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5. Standard Prestressed Beams As mentioned earlier the arrangements of the bridge are based on the available standard pretressed beams as shown in Appendix II. These comprise of posttensioned I beams and pre-tensioned inverted T beams. The choice between these two types of prestressed beams depends on the span and locality of the project. Pre-tensioned beams have the advantage of being cast in the factory under good quality control. But they can only be in short length probably not more than 20 m because of the difficulty in transporting them to the work site. Post-tensioned I-beams can span greater lengths and are best used when the bridge site is not easily accessible or remote. Casting and prestressing on site will solve the problem of transportation of the finished beams. 6. References

PETUNJUK: PPK

- Penolong Pengarah Kanan

K

- Kerani

JKK

- Jurutera Kerja Kanan

PB

-

Perekabentuk

Py

-

Penyemak

KP

- Ketua Pelukis

PL

-

OK

- Operator Kamera

JT

- Jurutaip

Pel.Pej.

- Pelayan Pejabat

P/TP

- Pengarah/Timbalan Pengarah

J/PP

- Juruteknik/Pelukis Pelan

Pelukis

Apart from the design codes mentioned earlier, the following are popular references used in the section: 1. Concrete Bridge Design - R.E. Rowe. 2. Introduction to Structural Design (Concrete Bridges - Derrick Beckett. 3. C & CA/CIREA Recommendation on the use of inverted TBeams and pseudo-box construction Wilson & Manton. 4. The Analysis''of Right Bridge Decks subject to Abnormal Loading - Morrice & Little. 5. Design of Prestressed Concrete Structure T.Y. Lin. 6. Standard Bridge Beams for spans from 7m-to 36m - Sommerville. 7. Foundation & Pile Design - Tomlinson.


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APPENDIX 1 A

A.

CARTA ALIRAN KERJA REKABENTUK PERMULAAN STRUKTUR JAMBATAN

MULA

Terima permohonan, buat keputusan untuk direkabentuk oleh Unit Jambatan

PPK

Buka fail, kandungkan surat

K

JKK

Kaji dan lantik perekabentuk dan penyemak

PB Tidak

Kumpul maklumat struktur melintasi sungai Ya

PB

Minta ‘bridge proforma’ Buat perkiraan haiderologi

PY

Semak Perkiraan haiderologi

PB

Rangka Pelan Cadangan

PY

Semak Pelan Cadangan

PPK

Luluskan Pelan Cadangan? Ya

Tidak

KP

Lantik Pelukis

PL

Lukis Pelan Cadangan

KP

Semak dan tandatangan pelan cadangan

PB

Semak dan tandatangan pelan cadangan

*


Bersambung dimuka surat sebelah

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APPENDIX 1 A

CARTA ALIRAN KERJA REKABENTUK PERMULAAN STRUKTUR JAMBATAN

*

PPK

Sambungan dimuka surat sebelah

Luluskan Pelan Cadangan?

Tidak Ya

OK

Buat salinan pelan cadangan

PB

Tulis surat

JT

Taip Surat

PB

Semak dan tandatangan ringkas

PPK

K

Pel. Pej.

TAMAT

Tandatangan surat

Semak dan failkan surat / lukisan

Hantar surat / lukisan

Proses kerja rekabentuk terperinci struktur baru


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APPENDIX 1 B

B.

CARTA ALIRAN KERJA REKABENTUK TERPERINCI BARU UNIT JAMBATAN MULA

Dari Proses Kerja Rekabentuk Permulaan

PPK/JKK

Terima ulasan dan kelulusan cadangan

Cadangkan konsep struktur / rekabentuk piawai

PB Tidak

Ya

JKK/ PPK

Luluskan ?

PB

Siapkan rekabentuk terperinci

PY Tidak

Semak perkiraan Ya

JKK

Luluskan?

Atur kerja dan lantik pelukis

KP

PL

Siapkan lukisan terperinci

Tidak

KP

Semak dan luluskan Ya

PB

Semak dan tandatangani

PY

Semak dan tandatangani

JKK

Semak dan tandatangani Ya

Tidak

PPK

P/JP

PPK/JKK

O.K

TAMAT

Luluskan

Tandatangani Lukisan

Serah pada O.K

Buat Salinan

Proses Kerja Penyediaan Dokumen Meja Tawaran *



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APPENDIX 1 C

C.

CARTA ALIRAN KERJA PENYEDIAAN DOKUMEN MEJA TAWARAN UNIT JAMBATAN

MULA

Dari Proses Kerja Rekabentuk Terperinci

Terima salinan lukisan

JKK

Deraf/pinda penentuan dan jadual bahan

PB Tidak

Ya Luluskan format penentuan dan jadual bahan ?

JKK/ PPK

KP

Arah bagi kerja

J/PP

Buat ‘taking off’, abstracting dan billing’

KP

Semak ‘taking off’, abstracting dan billing’

PB

Susun dokumen meja tawaran

PY

Semak dokumen meja tawaran

JKK

Semak dokumen meja tawaran

PPK

Luluskan?

Tidak

Ya

JT

Taip dokumen

PB

Semak

JKK

Luluskan

Tidak Ya

*



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APPENDIX 1 C

C.

CARTA ALIRAN KERJA PENYEDIAAN DOKUMEN MEJA TAWARAN UNIT JAMBATAN

*

Sambungan dari muka surat sebelah

Tulis surat

PB

Tulis surat

JT

PB

Semak surat dan tandatangan ringkas

PPK

Tandatangan surat

Tidak Ya

K

Pel.Pej

Pb/kp

Failkan surat

Hantar surat/dokumen

Susun semula data rekabentuk dan jilid dokumen untuk rekod

TAMAT


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STANDARD PRESTRESSED BEAMS AVAILABLE IN THE BRIDGE UNIT

NO.

NO.BEAM

OVERALL LENGTH-(m)

EFFECTIVE LENGTH-(m)

1.

I-BEAM

31.24

30.33

2.

1 - BEAM

25.00

24.23

3.

INVERTED T

18.90

18.59

4.

INVERTED T

16.76

16.53

5.

INVERTED T

12.50

12.34

6.

INVERTED T

9.45

9:29

LIST Of RELEVENT B.S CODES & B.E TECHNICAL MEMO FOR BRIDGE DESIGN:

B.S

B. E

1. LOADING

B.S 153 : Pt3A ' 1972.

1/77.

2. R.C DESIGN

CP 114

1/73

3. P.C DESIGN

CP

115

4. PRECAST BEAM

CP

116

5. COMPOSITE CONSTRUCTION

CP 117: Pt 11

6. FOUNDATIONS

CP

7,, ILASTOMETRIC BEARING 8. NEW BRIDGE CODE

2004

B .S 5400

"

2/73 -

1/76 r -

9. EARTH RETAINING STRUCTURE

-

3/78

10. PARAPET

-

5

11. DESIGN CRITERIA FOR FOOTBRIDGES

-

1/78

12: EXPANSION JOIKTS

-

3/72



LIST OF 0. I.0 HYDROLOGICAL PROCEDURES FOR HYDROLOGICAL CALCULATION:1. HP 1

- ESTIMATION OF THE DESIGN STORM

2. HP 5

- RATIONAL Mtd.

3. HP 11 - UNIT HYDROGRAPH Mtd. 4. URBAN DRAINAGE DESIGN Stds AND PROCEDURES FOR PENINSULAR MALAYSIA 5. HP 4 - REGIONAL FLOOD FREQUEN CY Mtd. PROFORMA FOR BRIDGE DESIGN Federal:.................... State:.................... Bridge No: ................ S7ungai: ..........*........ State:.,................... Route or Road:............................ at. Milestone:................ 1. STREAM: (a) FLOOD LEVEL Normal R.L. ........................ Exceptional R.L.................... . Date: .................. (b) NORMAL WATER LEVEL - R.L............... ........... (c) POSSIBILITY OF DEBRIS DURING FLOODS:........................................ (d) NORMAL VELOCITY ....................... h/Sec . ................ ....... 2. PLANS FORWARDED: (a) Site Plan ........................... Drg. No:............................. (b) Longitudinal Section on: (i) Centre line of Bridge (ii)' 15 m. on either side of centre line of bridge to a distance of 150 m. on either bank of stream. Drg. No. .......................... (c) Cross-section through road embankment near abutments. Drg. No.................................... (d) Plan Showing: Cawangan Jalan, Ibu Pejabat JKR, K.L

(i) Stream course for 100 m. on either side of bridge (ii) road approaches within 100 m. of bot ends of bridge. Drg. Not .......................... (e) Plan showing details of existing piers and abutments and other obstructions, Drg. No:....................... 3 BRIDGE: Proposed deck level. R.L..................... Foot paths: Carriageway: clear distance between kerbs. 4. CONSTRUCTION: State whether: (a) Divided deck type is required: .............................. or (b) Alternative arrangemcnt will be made for traffic di viation during construction:......................................... ............................................................ 5.. SERVICES: Accommodation required for: (a) water mains. Size:........................ (b) Electricity cab1c ducts. Size:......................................... (c) Telephone ducts. Size:.......................................... (d) Lighting standards:.................................. 6. GROUND CONDITIONS: (Preliminary information, if available) Whether (a) Open type foundations feasible ............... (b) Good bearing strata. likely at R.L......................... ........ (c) Extremely poor ground ............................ (d) Mackintosh probes details 1n Drg. No: ..................... ......... 7.STIPULATIONS BY OTHER AliiHGR'.k IES I IF ANY: ................... .............................................................. .. ............................................. .......................... .............................. Page 17




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NOTES ON HYDROLOGICAL CALCULATIONS FOW- BRIDGE DESIGN

important catchment area characteristic in comparing f18od magnitudes.

1. INTRODUCTION

Main channel slope can be determined by simple measurement from topographic maps. For non-uniform slope, 'weighted mean slope' can be used though it can be argued that in the preparation of H.P. No. 5 the 'rough' slope had been used~so it would be more appropriate to use the 'rough' slope in the calculation.

In the design of a hydraulic structure, hydrological calculation is necessary to determine the rate of flow or discharge that the hydraulic structure will be required to accomodate.

.

The design discharge is a 'hydraulic load' analogous to the structural load in a structural design.

2.3 LAND USE

In a bridge design, we need to determine the design flood discharge for a certain Return Period so we can propose a bridge with the deck level well above the flood level.

The effect of urbanization and land development on peak flow depend upon the percent of the area made impervious and the changes made in the drainage pattern through the installation of storm sewers and modification of surface channels:

Besides this, we have to calculate the flood velocity to determine if the river bed is susceptible to scouring. 2. FACTORS AFFECTING FLOOD RUNOFF

DID HP No.5 has recommended as a general guide, factors to allow for varying amounts of change from undeveloped vegetation to agricultural crop. (Table 3)

2.1 SIZE

2.4 SOIL TYPE & SURFACE INFILTRATION

The size of a catchment area has an important bearing on the response of the catchment to rainfall, and consequently on the methods used to predict flood runoff.

The type of soil and its surface infiltration capacity affect the amount of runoff in the catchment area. These factors are taken into consideration by the Runoff Coefficient (C).

Topographic maps are valuable aids in obtaining the size of -cafchrnent areas.

2.5 STORAGE

In the Rational method (HP No.5) the size of catchment area is limited to 0.5 - 40 sq. miles. Return Period is the average interval of time (in years) between the years that contain an event, greater than or equal to the one under consideration. It is a statistical measure of the probability of occurence of a.flood under consideration. 2.2 SLOPE Many investigations have found that next to catchment area size, some index representing the slope of the catchment area is a very Cawangan Jalan, Ibu Pejabat JKR, K.L

Storage within a catchment area may be detention storage, which is the rainfall lost in filling small depressions in the ground surface; storage in transit in overland channel flow, or storage in ponds, lakes or swamps. Storage may also occur in flood control structures like reservoirs. The effect of storage on peak flows can be quite large. However, this effect has not been taken into account in DID HP. No. 5, such that catchment areas where storage effect is expected to be serve as in the case of reservoirs, DID HP No.5 should not be used. Page 21



Helpful data can then be obtained from the controlling public agencies. For urban drainage modified rational method can be used in which storage coefficient.(Cs) shall be multiplied by basic Rational Method formula Q = CSCiA Where Cs =

2 tc __________ 2tc + td

and tc is the time of concentration td is the time of flow in the drain but, C is the composite runoff coefficient and shall be determined as follows C = A1 C1 + A2 C2......An Cn _______________________ ' A Al, A2 etc. are n areas, each of relatively uniform land use or Furface character, comprising the total area A. And C1, C2 etc. are the corresponding runoff coefficients obtained from table below. 2.6 RAINFALL The total amount of rainfall is most important in producing peak flows from large areas, while the intensity of rainfall is . most important in producing peak flows from small areas. Catchment area characteristics and antecedent conditions have a major effect on the proportion of rainfall which becomes runoff.

designer are: (a) Photographs of structures during flood (b) Maximum flood level (c) Distribution of flow and approximate velocities in different sections of the stream (d) Duration of flood (e) Magnitude of flood (f) Scour, erosion & sediment deposits (g) Damage to structures & adjacent property These information may be obtained from the local residents and.the related local public agencies like the D.I.D. 4. STATISTICAL METHODS IN THE ESTIMATION OF FLOOD MAGNITUDES Where actual records of runoff from historical floods extending over long periods are available, such records may be analysed to furnish the basic design data. Unfortunately, in the majority of cases adequate runoff records are not available and estimated of storm runoff by statistical method has to be used. 3 methods have been established by the DID, Malaysia: (a) Rational Method (Hp No.5) (b) Unit Hydrograph Method (Hp No.11) (c) Regional Flood Frequency Method (Hp No.4)

3. BLOOD HISTORY HISTORICAL FLOODS The history of past floods and their effect on existing structures are useful in making flood hazard evaluation studies, including needed information for sizing our structures. Records of the past floods that are useful to a Cawangan Jalan, Ibu Pejabat JKR, K.L

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Table 1 Rational Method Runoff Coefficients for urban centres

Land Use

Runoff Coefficient

Business:City Areas Fully built-up and shophouses

0.90

Industrial:Fully built-up

0.80

Residential:4 houses/acre 4-8 houses/acre 8-12 houses/acre 12 houses/acre Pavement Parks (normally flat in Urban Areas) Rubber Jungle (normally steep in urban areas) Mining Land Bare Earth

0.55 0.65 0.75 0.85 0.95 0.30 0.45 0.35 0.10 0.75

5. RATIONAL METHOD (HP No. 5) 5.1 ASSUMPTIONS 5.1.1 Homogeniety of rainfall in terms of time and space 5.1.2 The maximum rate of runoff for a particular rainfall intensity occurs if the duration of rainfall is equal to or greater than Tc: *'Tc = Time of concentration is defined as being the time taken for the most remote part of the catchment to contribute to flow at the design point. N.B. Minimum Tc recommended in HP No. 5 is 30 minutes. 5.1.3 The maximum rate of runoff from a specific rainfall intensity whose duration is equal to or greater than TC is directly proportional to the rainfall intensity. Cawangan Jalan, Ibu Pejabat JKR, K.L

5.1.4 The frequency of occurence of the peak discharge is the same as that of the sample intensity from which it was calculated. 5.1.5 The coefficient of runoff C remains constant for all storms on a given watershed. (Catchment area) 5.2 ANALYSIS OF POINT RAINFALL Point rainfall is the rainfall records taken at a single gauging station. The DID Malaysia had collected rainfall records for the peninsular and produced isopleths after statistical analysis These isopleths can be made use of to calculate the storm intensity for various return period and duration.

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It is customary in engineering practice to assume that, point . rainfall values are applicable to areas up to 1sq mile and for larger areas reduced values are to be used (Areal Reduction Factor - Table 2).

(f) Read off values of: X(10, ½ ) ) X(10,2 ) ) if Tc is between X(100, ½) ) ½ hr. & 2 hrs. X(100,2 ) )

5.3 PROCEDURE 5.3.1 INFORMATION . (a) Cross-sectional drawings and other site plans (b) Topographic maps (c) Design Profoma: (i) History Flood (ii) Channel characteristic (iii) Client's requirements (d) DID Hydrological procedures (Hp No. 1 & Hp No. 5) 5.3.2 HYDROLOGICAL CALCULATION 5.3.2.1 Estimation of the design rain storm (use of Hp.. N0.1) (a) Adopt Return Period T = 100 years (b) Determine Time of Concentration

X(10,2 ) ) X(10,24 )) if T c is between 2 hrs. & 24 hrs. X(100,2 ) ) X(100,24 ) )

AND SO FORTH............ (g) Plot the above values in graphFig. 10 (Fig. 9 of Hp. No.1) (h) Read off values of X(2, TC ) X(10, TC) X (20, TC ) X(100, TC ) (i) Compute confidence Limit D = X(20) - X(2) Limit = 0.43 D (j) Max X(100) = X(100) + 0.43D * T can be calculated from Hp. No. 8 but it is the JKR practice to adopt T = 100 years. 5.3.2.2 Flood Estimation

TC = 0.434 A0.117L ____________ S 0.467 NB Note that A is in sq. miles L is in miles S is weighted .mean slope (in percent) (c) Obtain values of X(T,t) from figs 1-8 for T = 2, 20; and t to envelope value of TC. (i.e. t 1,

Use of HP No. 5 (a) obtain values of X(10) & Max X(100) (b) Compute 110 = X(10) ______ TC and reduce the intensity accordingly by the appropriate Areal Reduction Factor Table 2 - (Table 8 of Hp No.1) (c) Evaluate C from fig. 11 &.,12 (d) Compute i100 = X(100) _______ TC - again applying the appropriate Areal Reduction Factor

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(e) Compute Peak discharge Q100 - F (C x i 100 x Ac), value of F from table 3 being Land-use Factor. Note that Ac in Acres (1 sq mile = 640 acres)

D = X(20) - x(2) Standard error = 0.43D based on 20 years record and return period of 100 years.

5.4 RELIABILITY OF THE RATIONAL METHOD 5.4.1 It cannot be over. emphasised to state that the results obtained from the Rational Method should not be adopted indiscriminately because of the following uncertainties in the method: 1. There is a degree of uncertainty Jinvolved in the initial computation of the qT & iT frequency distributions in the preparation of fig. 12 for values of Runoff coefficient (C) 2. In developing the components of the procedure, the TG relationship and the selection chart for C, averaging is carried out in semi quantitative fashion only. Lastly, it must be emphasised again that the use of any flood estimation procedures must be complemented by sound engineering judgement and experience. Flood information collected from the local residents in the vicinity can be very useful. 5.4.2

CONFIDENCE LIMITS

The computed value of an event for a certain return period by Hp. No.1 is not the 'real' value, and has a certain statistical uncertainty attached to it. The standard error can be computed based on the work by Robertson: This standard error can be used to construct two control curves such that 2/3 of the estimate would be expected to fall within this range. Cawangan Jalan, Ibu Pejabat JKR, K.L

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TABLE 2:

AREAL REDUCTION FACTOR FA (FROM TABLE 8 OF HP 1)

CATCHMENT AREA Ac (sq miles)

STORM DURATION t (hrs) 1/2

1

3

6

24

0

1.0

1.0

1.0

1.0

1.0

50

0.69

0.80

0.90

0.93

0.95

100

0.61

0.72

0.84

0.89

0.93

150

0.58

0.68

0.82

0.86

0.92

200

0.67

0.80

0.84

0.92

250

0.66

0.80

0.84

0.92

300

0.65

0.80

0.84

0.92

350

0.80

0.84

0.92

400

0.80

0.83

0.92

TABLE 3:

LANDUSE FACTOR F (FROM TABLE 2 OF HP 5)

DEVELOPMENT TO AGRICULTURE FROM JUNGLE IN PERCENT

F

0-25

1.00

25-50

1.05

50-75

1.15

75-100

1.20


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6. UNIT HYDROGRAPH METHOD (HP. No. 11) This method estimate total flood hydrograph for ungauged rural. catchments: This procedure is not applicable to urban catch ments. one advantage of this method is that it can be used to distribute runoff from storms of varying temporal pattern. The disadvantage is that.it is fairly tedious to apply. 6.1 REQUIREMENTS 1.

It should estimates: (i) The peak flow (ii) The volume and time distribution of runoff for various recurrence intervals. 2. Account for significant differences in the catchment characteristics that effect floods. 3. Utilize catchment data that can be readily determined from topographical maps. 4. Should be simple and relatively fast to apply. 6.2 PROCEDURE

4. Calculate design storm using HP. 1 (P in)XT t N.B. } for 3 hrs. storm } T is any design return Pin = XT 3 } period say 50 or for 4 hrs. storm Pin = X T,4

} 100 yrs. }

5. Calculate direct runoff volume, Q (i) Design storm < 3 ins. Q = 0.33 P ins. (ii) Design storm > 3 ins. = P2 ins. --------(P+6) 6. Calculate Peak Discharge,.gp = Dp x A 640 x Q ----------------------- ft 3 /Sec. (Lg + D/2) Where Dp = peak ordinate of the dimensionless hydrograph i.e. charateristics of the catchment (table 5) D = Duration of storm 7. Add baseflow component of 5 cusecs per sq. mile. Table 4: Values Ct and n For Equation

1. Determine the catchment group (From table 4) 2. Compute: (i) L - Length of stream from the out let to the catchment boundary (mile) it (ii) Lc - Length of stream from outlet to the. catchment centroid (See fig. 13) (iii) A - catchment area (iv) S - Stream slope (Formula is as in egn.(1) 3. Calculate catchment lag, Lg is the time from half the duration of rainfall excess to half the volume of direct runoff. Lg=- Ct x [ LLS]

n . . . . . . (2) .

--------S


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Table 4: Values Ct and n for Equation

Catchment Type

Ct

n

Group 1

Whole catchment very steep and covered in virgin jungle

2.0

0.35

Group 2

Upper catchment very steep and jungle covered, lower catchment reaches hilly and covered predominantly with rubber

4.0

0.35

Group 3

Whole carchment undulating with variable vegetation including jungle, rubber and agricultural development

8.0

0.35

Table 5

: Values of Dp, Tb and Tp

Catchment Type

Dp

Tb

Tp

Tp/Tb

Group 1

1.06

1.89 C

0.94C *

0.50 *

Group 2

0.89

2.24 C

0.87C

0.39

Group 3

0.75

2.67 C

0.58C.

0.22

* Adapted for design flood estimation


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7. Regional Flood Frequency Method (Hp No.4) A total of 11 regions (F1 to F11) have been defined in Peninsular Malaysia, within which reasonably consistent regional flood frequency relationship have been established. Thes regions are shown on plate 1, together with location of the gauging stations used in analysis. location of the gauging stations used in It has not been possible to provide rational flood frequency coverage for the whole of Peninsular Malaysia. This is especially so for the areas between the coastline and the foothills of the central and western mountain range. On such areas data in respects of flood peaks are very difficult to obtain because of large flood plain storage and tidal effects. 7.1 Use of Procedure This procedure may be used for estimating the flood frequency distribution within any of the regions shown on Plate 1. There are two situations, for which different methods are used-to make the flood estimate: Case 1 : Stations with sufficient data to define the mean annual flood Case 2 : Stations with zero or very little streamflow data. ' Example of Case 1 Station No. 4442 Station Name : Sg. Langat at Kajang Catchment Area : 148 sq. miles (from Plate 1) Flood frequency Region: F4 Mean Annual flood: 4503 cusecs (From Appendix A) From Figure 14, using the region F4 flood frequency line, prepare Table 6 shown on page 47.


Example of Case 2 Station: Unnamed point on Sg. Seminyih Flood Frequency Region: F4 (from Plate 1) Catchment area: 148 sq. miles (NB. same as for 4442) . Mean annual flood (from Figure 16): 3600 cusecs From Figure 14, using the region F4 flood frequency line, prepare Table 7 shown below: Example of Case 3 (67% confidence limit) Take the same station as for case 1 'Q20 = 6260 ) Q2 = 4360 ) From Fig.18 R = 1900 ) R = 1900 = 425 V n f 20 Standard error of the estimate of Q2 = Q5 = Q10 Q20 Q25 Q50

0.54 x 425 = 0.86 x 425 = = 1.23 x 425 = = 1.73 x 425 = 0.43 x 1900 = 0.43 x 1900

230 366 522 = 736 = 820 = 820

Control curves are plotted on the estimated flood frequency curve for case 1 shown on Fig.18. The control curves indicate that twothirds of the (say) Q25 estimate made from data samples of length 20 yrs. would lie in the range 6439 t 820,cusecs, i.e. from 5619 to 7259 cusecs. 7.3 Limitation 1. This procedure applies only to the catchment areas indicated by the position of the mean annual flood - catchment area lines on figures 15, 16, 17 and reproduced in Table 8 below:

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Table 6: Reconstituded flood frequency estimates (Region F4, Case 1) T (y rs)

QT/Q2.33

QT(Cusecs)

2.33

1.00

4503

5

1.16

5223

10

1.27

5719

25

1.43

6439

50

1.54

6934

100

1.64

7385

The Flood frequency curve reconstituted for station No. 4442 using the data from Table 6 is shown on Figure 18.

Table 7: Reconstituded flood frequency estimates (Region F4, Case 2) T (yrs) QT/Q2.33 QT(Cusecs) 2.33 1.00 4503 5 1.16 5223 10 1.27 5719 25 1.43 6439 50 1.54 6934 The Flood frequency curve reconstituted for the unnamed location on Sg. Semenyih using the data from Table 7 is shown on Figure 18.


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Table 8: Range of Flood Frequency Region


Catchment Area applicability for each region Range of Catchment Area for which procedure is suitable (sq. mile)

F1

30 - 1500

F2 F3 F4 F5 F6 F7 F8 F9 F10

30 - 300 100 - 450 45 - 600 30 - 200 45 - 1200 80 - 400 20 -1000 40 - 2000 40 - 3000

F11

2000-- 10,000


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APPENDIX A Region F4

MEAN ANNUAL FLO O D DATA

MAXIMUM RECO RDED FLO O D DATA Maximum discharge data

STATIO N PERIO D O F NO

RECO RD

Station

Regional

Q .33(cusecs)

Q .33(cusecs)

Date

Gauge Height

cusecs

(ft.above m.s.t)

cusecs

Regional

Ratio to

per

Return

Regional

sq.ml

Period (yrs)

Q 50

0.98

3413

1947-1970

3650

2900

24.4.54

128.3

3950

31.8

41

4411

1949-1970

8110

6800

30.10.55

67.8

10800

25.6

80

1.05

4412

1947-1970

2130

2010

4.6.66

134.7

2530

35.1

10

0.83

4421

1950-1970

8820

8250

1.11.55

26.8

10900

19.5

14

0.87

4422

1961-1970

4000

2900

26.11.67

118.5

5000

40.3

>100

1.13

4431

1948-1970

4000

5010

27.10.57

33.6

5600

20.4

4

0.74

4432

1948-1970

5220

3920

28.4.52

93.5

7450

39.4

>100

1.25

4433

1948-1970

1180

1500

14.9.64

103.2

1600

34

3

0.7

4434

1948-1970

1460

1700

2.2.51

107.8

1680

30

2

0.65

4441

1949-1970

4800

7450

11.6.54

27.2

6915

14.5

2

0.61

4442

1948-1970

4500

3350

27.10.57

89.5

7500

50.7

>100

1.47

2170

2175

4.3.64

109.8

3190

38.9

36

0.97

4443

(FROM APPENDIX B HP" 4)

8 DETERMINATION OF THE FLOOD WATER LEVEL FLOOD WATER LEVEL AND VELOCITY 8.1. Manning's Formula: 8.1.1 Manning's Formula is used to calculate the flood Velocity of the main stream v = 1.49 (R) 2/3 (S o)1/2 n 8.1.2 The formula is strictly valid for cross-sections shaped like wide rectangles having approximately level bottoms 8.1.3 The hydraulic gradient is assumed to run parallel to the energy gradient (i.e. uniform flow) 8.2. Procedures 1. Draw out the cross-section of river at bridge site to scale on a graph paper.


2. Assume a flood level based on the past flood records (from Proforma) 3. Subdivide the cross-section according to marked changes in roughness. 4. Assign values of Mannings Roughness coefficienct to each'sub section (Table 9)." 5. Further divide the subsections according to marked changes in depth of flow and work out the areas (A) and wetted perimeter (P) for each sebsection Work out the Hydraulic radii for each subsection: R i = Ai -------Pi i = no of subsections. 6. Compute the velocity of each subsection by Manning's Formula.

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10. PRESENTATION OF SKETCH PROPOSAL

Maximum Permissible velocity or nonerrodible velocity is the greatest mean velocity that will not cause erosion of the channel body (Table 7). Vm is not to exceed this velocity.

The discharge capacity should be able to accomodate the peak discharge Q100. If Qc < . Q100 Repeat steps 2-8 by a ew trial flood level until Qc is slightly higher than Q 100 ,

At this juncture, we could have arrived at:-' 10.1 Proposed deck level (Having taken into account the depth off standard beams to be used; thickness of deck slab; premix; bearing and amount~of-freeboard) It is JKR practice to allow for a free board of 0.3-1.0m to cater for the debris brought along by the flood water. 10.2 Number of-spans-required-and the length of.each span. 10.3 .Whether .or not-bed protection is required. with these infomation. we should be able to put up a . sketch proposal. This sketch proposal is to be submitted to the client and the D.I.D for approval.

* If the mean velocity is ' her than the maximum permissible velocity this.can be rediced by using a longer span bridge. Should this turnout to uneconomical, bed protection should s be provided. 9 Computation of Back Water Curve When the crossing at the bridge Bite is constricted dire to the construction of a new bridgb, back water will be resulted causing a rise in water level above the calculated water level. This rise in water level (if it occurs) has to be taken into account in considering the deck level of the proposed bridge. This computation may not be necessary if there is no constriction causes by the new bridge. Steps for. such computation are available in the DID manual for 'Urban drainage design standard and procedures for Peninsular Malaysia'. Cawangan Jalan, Ibu Pejabat JKR, K.L

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TABLE 10. PERMISSIBLE VELOCITIES FOR DIFFERENT BEDMATERIALS

NATURE OF BED

PERMISSIBLE VELOCITY(ft/s)

CLAY

7

SANDY CLAY

5

VERY FINE SAND

2 TO 3

FINE SAND

3 TO 5

FINE GRAVEL

5 TO 6

ROCKY SOIL

10

ROCK

14 TO 20

GRASS - LINED

7.5

* EXTRACTED FROM DID “ URBAN DRAINAGE DESIGN STANDARD PROCEDURE FOR PENINSULAR MALAYSIA”


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APPENDIX

REFERENCES

NOTATIONS AS USED IN THE HYDROLOGICAL CALCULATION .

1.

A = Area of cross section of river Ac = Area of supplying catchment C = Runoff coefficient D = X (20).- X (2) . F = Land-use Factor FA = Areal Reduction Factor A h = Difference in level iT = Average intensity of the design rain storm of return period T years li = Incremental stream length L = Length of the main stream /n = Roughness coefficient p = Wetted Perimeter QC = Discharge capacity of a river cross section Q T= Peak Discharge of design flood with return. period T year R = Hydraulic Radius S, = Incremental Stream slope S = Weighted mean stream slope SO = Stream slope at bridge site t = storm duration T = turn Period Tc = Time of concentration Vm = mean stream velocity v = stream velocity X(T,t) = Rainfall depth of a storm with an estimated return period of T years and having a duration of t hours. X(T) = Rainfall depth of a storm with an estimated return period of T years the duration of which is specified elsewhere.


2.

3.

5. 4.

5.

T,D. Heiler, Estimation of the Design Rainstorm, D.I.D. Hydrological Procedure No. 1, Ministry of Agriculture and Fisheries Malaysia, 1973 T.D. Heiler and Chew Hai Hong, Magnitude and Frequency of Floods in Peninsular Malaysia, D.I.D. Hydrological Procedure No.4, Ministry of Agriculture and Fisheries, Malaysia, 1974 T.D. Heiler, Rational Method of Flood Estimation for Rural Catchments in Peninsular Malaysia, D.I.D. Hydrological Procedure No. Ministry of Agriculture and Fisheries, Malaysia, 1974 M.A.W. Taylor and Toh Yuan Kiat, Design Flood Hydrograph Estimation for Rural Catchments in Peninsular Malaysia, D.I.D. Hydrological Procedure No.11, Ministry of Agriculture, Malaysia, 1980 K.V. Lewis, P.A. Cassell and T.J. Fricke, Urban Drainage Design Standards and Procedures for Peninsular Malaysia, Ministry of Agriculture and Rural Development, Malaysia 1975.

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CHAPTER BRIDGE LOADING (A)

(B)

3

(ii) Live Loads (HA Loading and HB Loading)

Unlike in the design of Buildings where there is a complete and comprehensive code of practise, no such code for the design of concrete Bridges,ekist until recently. The recently published BS5400, for the design and construction of concrete Bridges, is yet to be adopted by the Bridge Unit Until such time, the design of bridges will be in accordance with BS 153: Part 3A (Loads) : 1973 and the C.P.114 (The elastic analysis method). Amendments and up-dating of the various a clauses in the BS 153 are carried out by the Ministry of transport. (United Kingdom) from time to time and are published in the Technical Memorandum. As such, when referring to the BS 153 for loading, the current Technical Memorandum must also be refered to in conjuction with-the BS153.

The Standard normal highway loading is called HA loading and the standard abnormal highway loading, the HB loading. Type HA loading comprises a uniform distributed load combined with a line load across the width of each traffic lane. This loading is considered to be adequate to represent the the effects of three vehicles, each 220 KN in weight, closely spaced, in each of two carriageway lanes followed by 100 KN and 50 KN vehicles. It should be noted here that Type HA Loading includes a 25% allowances for impact.

Loads Acting an a Bridge Superstructure

Type HB loading is usually expressed in Units per axle. The full type HB Loading (180 tonnes) is commonly expressed as 45 units (1 unit - IOKN).or part of it, 371 units (150 tonnes) or 30 units (120 tonnes).

The following Loads are to be taken into consideration when designing a bridge. They are:

Type.HB loading caters for the safe passage of an abnormally heavy vehicle of up to 180 tonnes gross laden weight with a configuration of wheels and axle as shown:

(i) Dead Load Dead Loads consist of structural dead Loads and superimposed dead Loads. Structural dead Loads are Loads due to the self-weight of the various structural components of the bridge. It should be noted here that a preliminary estimation of the sizes of the various structural components is necessary at this stage. The superimposed dead load consist of items like road surfacing road furniture, weight of services (water mains, Telecoms cables, electric cables ...... etc). -


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(iii) Loads due to centrifugal force On elevated roadway structures and bridges carrying highways that have sharp horizontal curvature, centrifugal force must be taken into account. This involves making assumptions about the speed and weight of vehicles, together with the intervals between them where the loaded length allows several vehicles in line. A judgement may be made on the intervals between vehicles, based on the information about stopping distances given in the highway code. The Technical Memorandum BE 1/77 specifies design forces to cover these conditions in anticipition of the requirements of BS 5400. (iv) Tractive/Braking Loads

(v)

stability problems will inevitably tend to be more sensitive-to wind loading. (vi) Load due to shrinkagey temperature.& creep These are horizontal loads due to forces generated in the beams/slab caused by shrinkage, temperature changes and creep in the concrete. (vii) Seismic Loads These are loads due to earthquakes. For Bridges designed in this country no seismic force are taken into consideration. The only exception to this, is the Penang Bridge where seismic Loads are considered. Procedure for determination of loads on Bridge Superstructure

The longitudinal force on a bridge structure result from the traction or braking of vehicles at the level of the carriageway surface. It is applied horizontally to the carriageway surface.

STEP 1 Determine the dead loads & superimpose dead loads of all structural components.

Wind Loads Wind forces though rarely significant in small-span and medium-span bridgeworks, can be critical in bridges like the suspension type where the span is large. Generally any structure which is sensitive to

STEP III Determine live loads'type,HA & HB. '


STEP II Determine width and number of traffic lanes

STEP IV Determine Tractive load,

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STEP V Determine movement of beam due to temperature, shrinkage and creep and Ca1c . horiz. load.

follow is provided by the 'Summary of Loadings on Bridge Superstructure'. It should be noted here i that the total.dead loads are supported equally by the two supports.

STEP VI Determine loads due to wind forces ,

STEP II Width and number of traffic (design) lanes

Guide-Lines for Determination of Loads on Bridge Superstructure

Very frequently, views differ on what should be the carriageway width for live loads (HA & HB) considerations on a bridge and consequently, the number of traffic (design) lanes. It is the writerts opinion that the carriageway width of a bridge should be the clear distance between raised kerbs. However the more recent standards issued by the Road prdt\ch does not encourage the use of Kerbs but instead adopts 'Road Edge Stripping' to demarcate the traffic lane from the cycle/ pedestrian lane. In such cases, the carriageway width should include the cycle/pedestrian lanes. The justification for the inclusion being, there is a very likely possibility of an errant vehicle going onto the cycle/pedestrian lane, in the absence of road kerbs. (see fig. 1 and fig. 2).

Within the normal scope of design work carried out by the Bridge Section, the loads on a Bridge superstructure normally considered are: (i) Dead Loads (ii) Live Loads (iii) Tractive/Braking Loads (Longitudinal load) (iv) Wind Loads (v) Loads due to shrinkage, temperature & creep (S.T.C) The loads normally not taken into consideration are loads due to centrifugal force (except for sharp horizontal curvature) and even more infrequently, seismic loads. However, in special circumstances where a bridge is designed to be submerged, then the lateral horizontal force due to the water current and the bouyant force of the water need to be calculated and taken into consideration. STEP I Dead Loads The calculations for the dead loads of a bridge superstructure is quite straightforward. However a preliminary estimation of the sizes of the various structural components-, thickness of the deck slab, premix surfacing ... etc is required. This can be a problem for those designers attempting bridge design for the first time. The importance of an orderly and systematic approach to the calculations of dead loads cannot be overemphasized. Any haphazard approach may result in a structural component or item inadvertently left out. A good guide to Cawangan Jalan, Ibu Pejabat JKR, K.L

In the determination of Live Loads, two important items need to be obtained initially. (i) The number of traffic (design) lanes (ii) The width of each traffic (design) lanes There are two cases of carriageway width to consider: (i) Bridge with carriageway width of 4.60 m or more (ii)Bridge with carriageway width of less than 4.60 m In case (i) the number of traffic (design) lanes is obtained by dividing the carriageway width by 3.80 m and rounding up to the next whole number.

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Example Assume carriageway width = 7.5 m From Table in B.S. 153: Part 3A:1972 (pg. 5) Number of traffic lanes = 3 width per lane = 7.5 = 2.5 m 3 In case (ii) the number of traffic (design) lanes is obtained by dividing the carriageway width by 3.0 m. This implies that there will be fractional lane and the loading on the fractional lane will be proportional to the full lane. Example Assume carriage width = 4.20m , Number of lanes

= 4.2 lanes 3

Width per lane

= 4.2 = 3.0 m. 1.4

At this juncture, it is appropriate to give some clarification on the concept of traffic lanes. Rightfully, when designing, the lanes referred to should be called Design Lanes rather than traffic lanes so as.to distinguish it from traffic lanes in the context of Road design. From the above example Of carriageway width of 4.20m, it is clear why the distinction between the two must be made. In that example we have the number of lanes (for Loading Consideration) = 1.4 lanes, which would not be a possible number in Road Design. It would, in Road design, be a one lane or two lane roadway. This clearly demonstrates that the number of traffic (design) lanes of a bridge need not necessary be equal to the number of traffic lanes of a roadway. STEP III Live Loads HA & HB HA Loads When considering HA (normal live load)

and (ii) HA-KEL load (See fig. 3) and (iii) HAWheel loads. This implies that the HA-UDL load is uniformly distributed bothways equally i.e. longtudinally and across the width of the design (traffic) lane. The HA-KEL load is a line load acting across the width of the design (traffic) l6e. An important point to note here is that the HA-KEL load is a movabl load (along the span). The HA-KEL load must be placed in such a position so as to cause worst effects. For example, in the design of abutment or pier the HA-KEL must be positioned over the abutment or pier. In beam design however, the HA-KEL must be positioned mid-span. To wheel loads each 112KN force in line transversely to the direction of traffic flow spaced at 0.90m centres and having a contact area of 375 mm x 75 mm, the smaller dimension being in the direction of travel, to be used in the following cases: (a) Where the member supports a small area of roadway such that it may be called on to carry the weight of one or two wheels, and where the proportion of distributed load and knife edge load which would be allocated to it is small and on cantilever projections not exceeding 1.80m. (b) Where deck slabs are designed as supported on all four sides and the distance between supports in one directions is less than twice the distance in the other direction. The values for HA-udl (spanwise) and HAKEL (across the width of lane) are obtained from Table 1 and Fig. 1 of B.S. 153. However the values obtained need to be reduced by the factor 3 for lanes less than 3.Om width for HAUDL values (W= width of design lane) and for HA-KEL the values are 40KN/m (across widths/lane), for lane width less than 3.Om and 120 KN per lane for,lane width greater than 3.0m. .

loads, it is important to note HA loads onsist of three components; (i) HA-udl load Cawangan Jalan, Ibu Pejabat JKR, K.L

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Bridge with two or less design lanes shall be loaded with the full HA-UDL and HA-KEL loads. However for every additional design lane above two lanes, it shall be loaded with one-third (1/3) the full intensify. (see Fig.4). The relevant clause pertaining to this rule is clause 4.1.3. Of the B.S. 153. The following examples will illustrate more clearly the computations for HA-UDL and HAKEL loads. Case (i) Design (traffic) lane width 3.0m. or less Assume: (a) Design' (traffic) lane width = 2.70m(w) (b) Number of Design (traffic) lanes = 3 (c) Span of Bridge = 31.O m From Table 1 and Fig.1 of B.S. 153, HA-UDL = 28.5 KN/m (spanwise, per lane) HA-UDL (Reduced) = 28.5 x 2.70 = 25.65 KN/m (per lane) 3 HA-KEL (Fig.1) = 40 ICN/m (across width of lane) HA-UDL.(for first two lanes) = 25.65 x 31.0 x2 = 1590.3 KN HA-UDL (for third lane) = 25.65 x 31.0 x 1 x 1/3 = 265.05 KN Total HA-UDL = 1590.3 + 265.05 = 1855.35 KN HA-KEL (for first two lanes) = 40 x 2.70 x2 = 216 KN HA-KEL (for third lane) = 40 x 2.7 x 1 x x 1/3 = 36 KN Total HA-KEL = 216 + 36 = 252 KN Case (ii) Design (traffic) lane width greater than 3.Om assume:

(b) Number of Design (traffic) lanes (c) Span of Bridge = 31.0m.

=3

From Table 1 and Fig. Y of B.S. 153, HA-UDL = 28.5 KN/m (per lane) - HA-KEL (Fig.1) = 120 KN per lane. HA-UDL (for first two lanes) = 28.5 x 31.0 x 2. = 1767.0 KN HA-UDL (for third lane) = 7R-5 x31.0 x 1/3 = 294.5 KN Total HA-UDL = 1767 + 294.5 = 2061.5 KN HA-KEL (f6r first two lanes) = 120 x 2 = 240 KN HA-KEL (for third lane) = 120 x 1 x 1/3 = 40 KN Total HA-KEL = 240 + 40 = 280 KN HB Load The configuration of axles and wheels of a HB vehicle is as shown in Fig. 5. The load per axle is 450 KN and the total weight of the HB vehicle is 1800 KN. Very often the full weight of the HB load is also expressed as units per axle. The full HB load is referred to as 45 units . (1 unit = 10 KN) or part of it, say, 37J units HB. (375 KN/axle). Like the HA-KEL, the HB load is a movable load. For the design of abutment/pier or beams, the vehicle must be placed in such a position so as to cause the most adverse effects. (See Fig.6). In Bridges designed (checked) for HB loads, the Live Loads to be adopted for design will be either loads due to HA (Normal) or HB (abnormal) loads, depending whichever is greater. In Bridges designed (checked) for HB loads, the Live Loads to be adopted for design will be either loads due to HA (Normal) or HB (abnormal) loads, depending whichever is greater.

(a) Design (traffic) lane width = 3.2m (w) Cawangan Jalan, Ibu Pejabat JKR, K.L

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STEP IV Determination of Tractive/Braking Load This is horizontal force acting longitudinally on a bridge deck generated by sudden braking or traction of vehicles (see Fig.7) on the bridge. It is even more severe if the vehicles are heavy. The determination of this Tractive load is simple enough and the relevant clause in clause 10 of the B.S. 153. However the present JKR Practice predetermines a maximum value of 253 KN for tractive load for both HA and HB (45 units) Loadings. This is a slight departure from the B.S. 153 where the maximum load is 450 KN. The reason for this adoption of a smaller load is, in my opinion,. due to the present system of control and approval of passage of HB- Class of vehicles over a public road bridge. Any heavier than normal load intending to use any bridge has got to seek prior approval of JKR authorities. A condition normally imposed will be that the abnormally heavier vehicle to travel along the bridge centre-line at a very slow speed. No other vehicles will be permitted to use the bridge during this time. In such circumstances, the force due to sudden braking and traction is reduced to a minimum or none at all. Hence the adoption of a smaller load is justified. STEP V Loads due to movement of beam caused by temperature, shrinkage and creep They are horizontal forces acting longtudinally on a bridge generated by movement of beam caused by temperature, shrinkage and creep. The temperature and shrinkage coefficients adopted may be assumed to be universal values but the creep coefficients is dependent on concrete cube strength and cube strength at transfer (for prestressed beams). How much of shortening caused by shrinkage and creep that has occured at the time of casting of the beams and prestressing, is more Cawangan Jalan, Ibu Pejabat JKR, K.L

speculative than anything else. It is not uncommon to see designer's assuming a variety of figures. In the Bridge sectin we normally assume two-thirds (2/3) shrinkage and half (1) creep has(already occurred at the time of placing of beams. (See Fig.8). Therefore the actual beam movement, = Temperature shortening + shrinkage + creep 3 2 Knowing the actual beam movement, Plan area of elastomer and it's-shear Modulus, (for that particular 'Hardnesl';of elastomer) the horizontal force due-to shrinkage, Temperature and Creep, (commonly abbreviated to S.T.C.) can be determined. (See Fig.9). Shrinkage and creep can act in.only one 'direction but temperature can act in ;either direction, longitudinally. STEP VI Loads due to Wind Forces Generally, structures that possessed stability problems, like the suspension bridges, will be sensitive to wind loads. For the types of bridges designed in this section, wind loads are not critical but nevertheless they have to be taken into consideration of design purposes. Only the longtudinally component of the lateral wind force is taken into consideration. The lateral horizontal'wind force is normally omitteddue to the fact the ratio of the total vertical forces to the lateral horizontal forces is so large that stability of the structure can be provided by the sheer weight (Live Dead Load) of the structure itself. In the calculations for wind forces the area of superstructure (AW/s) normal to the direction of the wind in the windward side will be required. This AW/s will normally be made up of the height of the beam thickness of deck slab and the edge kerb, in the case of the bridge is of the metal. railings type or plus concrete parapet height if it is of the concrete parapet type. Page 61



The height of the live load is taken as 2.50m from the top surface of the deck and shall be assumed to occupy the span of the bridge. Thus, the area of live load (AL.L.) normal to the direction of the wind is = 2.50 x span of bridge. Case should be taken to ensure that scree,ing effect of the concrete parapet on the live load is taken into conside-ation. Hence the AL.L. always refer to the net exposed area of live load. In the case where the concrete parapet is used, then AL.L,= (2.50-0.80) x span of bridge. (Assuming concrete parapet height approx. = 0.80m).

the superstructure and half of the lateral wind force on the live load. Longtudinal Wind Forcez[( 1/4 x 0.7 x Aw/s) + (1 /2 x 0.7 x AL.L) ] (1 + n/16)

References . B.S. 153: Part 3A = 1972 (Loads) CONCRETE BRIDGE DESIGNER'S MANUAL E. PENNELLS - 1981 LECTURE NOTES ON BRIDGE LOADINGS BRIDGE DESIGN COURSE - BANGI 1983.

Another factor just simply referred to as 'n' in the B.S. 153, (perhaps should be termed as the leeward side factor) is simply defined as the ratio of the distance between the windward girders (beams) to the leeward girders (Beams) to the height of the windward girder. This factor, n/16 , is always less than unity and is applied at the leeward side when determining wind forces on it. The following shows the derivation of the formulas shown i/n Fig. 10. A. Unloaded Case From B.S. 153, Wind Pressure = 1.4 KN/m2 on windward side, The lateral wind force = 1.4 x Aw/s on leeward side the lateral wind force = 1.4 x Aw/s x n 16 Since the two forces act in the same direction, the total lateral wind force = 1.4 x Aw/s x n/16 + 1.4 x Aw/s = 1.4 x Aw/s (1 + n/16) The longtudinal wind Force is simply taken as =1/4 of Lateral Wind Force. B. Loaded Case From B.S. 153, Wind Pressure = 0.7 KN/m2 . Here however, the area providing resistance to the wind will be (Aw/s + ALL ). As before; The total lateral Wind Force = 0.7 (Aw/s + AL.L) (1 + n/16). In this case, the B.S. 153 states that the longtudinal wind force should be taken as a.quarter of the lateral wind force on Cawangan Jalan, Ibu Pejabat JKR, K.L

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BS 153.: Part 3A: 1972 British Standard Specification for Steel girder bridges Part 3A. Loads 1. Scope of BS 153 . This specification is primarily intended to apply to the superstructure of simply supported steel bridges of spans up to 100 m. Where appropriate, the requirements of the specification may be adopted for larger spans or other types of steel bridges, but care should be taken, in these circumstances to make whatever amendments are necessary for fixity at the supports, continuity and other indeterminate or special conditions, such as, for instance, may apply to opening bridges.

load initially assumed shall be checked after the design is made and the design shall be revised as found necessary. In determining the dead load, actual ascertained unit weights shall be used, but if these are not available unit weights as given in 13S 648 may be used, as appropriate. 4. Live load . The live load is the weight of traffic and shall be of the type and magnitude specified. The following standard loadings shall be adopted where appropriate: 4.1 Standard highway loading 4.1.1 Loading. Standard highway loadings are given in Appendix A.

2. Forces 'to be taken into account For the purpose of computing stresses the following items shall, where applicable; be taken into account: (1) Dead load. (2)Live load. (3) Impact effect. (4) Lurching effect. (5) Nosing effect. (6) Centrifugal force. (7) Longitudinal force. (8) Wind pressure effect (9) Temperature effect. (10) Resistance of expansion bearings to movement. (11) Forces on parapets. (12) Erection forces and effects. (13) Forces and effects due to earthquakes, ice packs, subsidence and other similar causes. Subject to the provisions of other clauses, all forces shall be considered as applied and all loaded lengths chosen in such a way that the most adverse effect is caused on the member under consideration.

These are: Type HA. Equivalent lane loading which is the normal design loading for Great Britain but may be varied in intensity where conditions are other than, those prevailing in Great Britain. Type HB. Abnormal unit loading. To be used when specified by the appropriate authority. In Great Britain 45 units shall be taken for bridges carrying the heaviest class of load This is an idealized load which allows for the weight of tractors accompanying trailers. 4.1.2

Width and number of traffic lanes to be used in conjunction with standard highway loadings . 4.1.2.1 Bridges having a carriageway width of 4.60 m,or more. Traffic lanes shall be taken to be not less than 2.30 m nor more than 3.70 m wide. The carriageway shall be divided into the least possible number of traffic lanes having equal widths as follows:

3. Dead load The dead load is the weight of the structure and any permanent loads fixed thereon. The dead Cawangan Jalan, Ibu Pejabat JKR, K.L

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Carriageway width (m)

No.of lanes

4.60 up to and including 7.40

2


3


4


5

4.1.2.2 Bridges having a carriageway width of less than 4.60 m. Where the carriageway on a bridge is less than 4.60 min width it shall be taken to have a number of traffic lanes. = width of carriageway in metres ---------------------------------------3.00 4.1.2.3 Where dual carriageways are carried on one single superstructure, the number of lanes on the bridge shall be taken as the sum of the number of lanes in each of the single carriageways, as provided in the table above. Where hard shoulders and marginal strips are provided these shall be considered as forming part of the carriageway and the number and width of traffic lanes calculated accordingly. Where marginal strips are provided without hard shoulders the number of traffic lanes shall be calculated after deducting the widths of the marginal strips from the overall width of the carriageway between the verges or raised 'kerbs; the intensity of loading on the marginal strip shall be taken as equal to that for the adjacent carriageway lane, except where the adjacent arriageway lane carries HB loading, in which case the marginal strip is unloaded.


4.1.3 Application of standardloading on a single superstructure Type HA loading Type HA loading shall be taken. to occupy one carriageway lane and to be uniformly distributed over the full width of the lane. Two lanes shall always be considered as occupied by full Type HA loading, while all other lanes shall be considered as occupied by one-third the full lane loading, except where other wise specified by the appropriate authority. Type HB loading. One lane shall be loaded with Type HB loading only. Where one carriageway only is carried on a superstructure, all other lanes shall be considered as occupied by one-third of the full lane loading, except where otherwise specified by the appropriate authority. Where dual carriageways are carried on one single superstructure two lanes on the carriageway not carrying HB loading shall be taken as occupied with full HA loading. All other lanes- shall be taken as carrying J, HA loading. 4.2 Standard railway loading Standard railway loadings are given in Appendix B, in imperial units only. Where the remaining calculations are in SI units, the values obtainedain imperial units shall be converted into SI units using the appropriate conversion factor. These are: Type RA. British Standard unit loading, for various gauges. Type RB. Total uniformly distributed load, including impact, for gauges of 4 ft 81 in (1.432 m) and over.

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case may be, and o the condition of loading for which the member being considered is designed.

BS 153: Part 3A: 1972 This loading is based on the Bridge Stress Committee's report of 1928, a brief pricis of which is given in Appendix D. It is suitable for railways in Great Britain and abroad with a gauge 4 ft 81 in (1.432 m) and over and with locomotive and track characteristics similar to those obtaining on the main railways in Great Britain. 4.3 Standard footway loading . The live load due to pedestrian traffic shall be treated as uniformly distributed over the footway. For loaded lengths up to and including 23.0 m it shall normally be taken as 4 kN/m' and for lengths over 23.0 m as the standard uniformly distributed loads given in Fig. 1 multiplied by a reduction factor of 4.0/31.5. Where crowd loading is likely the live load for the design of members exclusively supporting or forming the footway shall be taken as 5 kN/m'. In the case of highway bridges each part of the footway shall be capable of carrying a wheel load of 40 M, which shall be deemed to include impact, distributed over a contact area 300 mm in diameter; the working stresses shall be increased by 25 % to meet this provision. This provision need not be made where vehicles cannot mount the footway. 5.

(2)

No addition for impact shall be made to the live load due to pedestrian or equivalent light traffic. 6.


Impact effect on railway bridges A propriate additions shall be made to the live load specified in 4 for impact effects caused by the hammer blow of locomotives, rail joints, and track and wheel irregularities. In determining these additions due consideration shall be given by the engineer to the standard and maintenance of track and roiling stock, the types and characteristics of locomotives, and the. type and / characteristics. of the bridge. Type RB loading, which is suitable for the main line railways of Great Britain and other railways having similar locomotive and track characteristics, already includes an allowance for impact and co further additions shall be made. For all other loadings, including type RA, the additions for impact shall be specified by the engineer. For his guidance three methods of calculating the additions, those of Foxlee and Greet, the Government of India and the American Railway Engineering Association, are described in detail in Appendix C.

Impact effect on highway bridges Where Types HA ant"HB loadings given in Appendix A are not adopted, the allowance for impact on highway bridges shall be to en as follows: (1) An impact allowance of 25 % shall be added to the axle-load, or (where there is more than one lane of traffic) the pair of adjacent wheel loads, which produces the greatest bending moment or shear, as the

Where the loaded length required to produce the maximum stress in any member exceeds 30.0 m impact shall be ignored.

7

Lurching on railway bridges A separate allowance shall be made for lurching, unless this has already been included in the impact effect. 'Lurching results from the temporary transfer of Page 75



BS 153: Part 3A: 1972 part of the live loading from one rail to the other, the total load on the track remaining unaltered. The transfer shall be taken to increase the load on the rail which most adversely affects the member under consideration. The proportion QL of live load on one rail so transferred shall be calculated from the expression. 160k n QL = --------I +100 where k is a coefficient depending on the type of spring suspension, the weight and height of the rolling stock, and the type of construction and lateral rigidity of the bridge structure; n is the number of revolutions per second of the driving wheels of the locomotives (see Fig. 6, Appendix B); 1 is the effective span in feet, as defined in 1.4 of Part 4. NOTE. For conditions corresponding. to those ruling on the railways of Great Britain (4 ft 81/2 in gauge = 1.432 m gauge), and provided the structure is adequately stiffened laterally, k = 1/24 and n = 6 for maximum speed, but with a maximum value of QL of 0.25. For conditions other than those ruling on the railways of Great Britain, and where provision for a greater lurching effect is necessary, it is recommended that the value of the coefficient k be increased but to not more than 1/15 with a maximum value for the factor QL of 0.40. Where a member supports or assists in supporting more than one track, provision for the effect of lurching need only be made in respect of one of the tracks where these are two. or in respect of alternate tracks where there are more than two, the track or tracks selected being those on which the transfer of the load has the greatest effect on the member. Lurching need not be taken into account in the Cawangan Jalan, Ibu Pejabat JKR, K.L

case of an inner main girder assisting in supporting more than one track. No addition for impact shall be made to the lurching effect. 8. Nosing on railway bridges . An allowance shall be made for nosing, and this shall be taken as a single force of 10 tonf, acting horizontally, in either direction, at right angles to the track, at the rail level and at such a paint in the span as to produce the maximum effect in the member under consideration. This value is appropriate to the conditions obtaining on railways in Great Britain. In other cases the amount of force may be amended at the engineer's discretion. Vertical effects shall be disregarded. : On multi-track bridges, a single force as specified above shall be deemed sufficient. 9. Centrifugal force on railway bridges Where the track or tracks are curved, allowance for centrifugal action of the moving loads shall be made in designing the members, all tracks on the structure being considered as occupied. The centrifugal force due to the load per track shall be calculated from the following formula: w v2 C = ----------15R where C = the centrifugal force per lin ear foot considered as a moving load, acting at a height of 6 ft (1.83 m) above the level of the rails, unless otherwise specified by the engineer; w = the equivalent distributed live load, without impact, per linear foot per track; v = the allowable maximum speed of the train in miles per hour, as specified by the Page 76



BS 153: Part 3A: 1972 engineer; and R = the radius of the track curve in feet. No addition for impact shall be made to the centrifugal force. 10.

Longitudinal force on highway bridges The following longitudinal force resulting from the traction or braking of vehicles shall be taken as acting horizontally at the level of the carriageway surface, and having the following values for all widths of bridge. The force shall be applied over an area 3.00 m wide by 9.00 m long, or the length of the bridge, whichever is less, and in that position which will have the worst effect on the member under consideration. Type HA Loading Type HB Loading for 45 units

Span up 3.00m Spans above 3.00m

100 kN

} } 100 KN plus 17kN } for each metre of }450kN for all span over 3.00 spans mm but not } exceeding 253 kN } }

No increase for impact effect shall be made to the stresses due to longitudinal forces. Only one such force shall be considered. 11.

design of the structure, shall be taken as the larger of: (1) A force due' to traction of 20 % of the total axle loads on the coupled or driving wheels on one track without impact. When type RB loading is used, 20 units of type RA loading shall be taken for this purpose. (2) A force due to braking of 10 % of the total load on one track without impact. Where the structure carries two tracks, one up and one down, both tracks shall. be considered as being occupied simultaneously, and the force due to braking shall be applied to one track and, the force (in the same direction) due to traction to the other. Where the structure carries more than two tracks, the longitudinal forces shall be considered as applied to two tracks only, unless otherwise specified by the engineer, the worst case being taken as'regards its effect on any part of the structure. Some relief in the effect of the longitudinal force on the bridge and its supports may be taken into account where the tracks are capable of transmitting part of these forces to resistances outside the bridge structure. No addition for impact shall be made the longitudinal force.

Longitudinal force on railway bridges Provision shall be made for the forces due to traction and the application of brakes. These forces shall be considered as acting-on the rail, and, for the purpose of the


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BS 153: Part 3A: 1972 12. Wind pressure effects 12.1 General Where the effect of wind has to be taken into consideration, it shall be treated as a moving load (i.e. taken of such length along the span as to produce the maximum stress in the member under consideration) acting at the centroids of the exposed areas as defined below. The maximum effects from the wind blowing in either lateral direction on the loaded or unloaded structure., shall be taken, having regard to the disposition of the live load. For conditions normally prevailing in Great Britain the wind pressures specified below shall be used, but where owing to the position of the bridge or any special conditions the assumed wind speeds cannot be realized or may be exceeded, the engineer shall at his discretion specify different values. For this purpose the wind pressure shall be assumed to vary as the square of the wind speed. 12.2 For maximum lateral effect 12.2.1 On unloaded structures. A wind pressure of 1.4 kN/m2 corresponding to a wind speed of 40 m/s shall be '. taken as acting horizontally and normal to the sides of the bridge on a total exposed area of the superstructure made up of the following areas as applicable:


Windward girder, deck end bracing. The net exposed area in normal projected elevation of the windward girder, deck construction, bracing and parapet. Leeward girders. The following fractions (not exceeding unity) of the net exposed area in normal projected elevation of the leeward girder : n /16 when the windward girder is a plate girder n / 16 + 0.5 when the windward girder is a trussed girder where n = ratio of distance, centre to centre between the windward and outermost leeward girder, to the depth of the windward girder. Where there are more than two main girders, only that fraction of the area of the outmost leeward girder as calculated above shall be taken. In cases where a leeward girder projects in elevation beyond the windward girder, the full net exposed area.,of the projection as seen in elevation shall be treated as subject to full wind pressure. 12.2.2 On loaded structures. In arriving at the total effective area exposed to wind on a loaded structure, allowance shall be made for the screening effect, based on projected areas, of the structure on the live load, or of the live load on the structure, or of live loads on each other:

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BS 153: Part 3A: 1972 12.2.2.1 Highway and jootway bridges. A wind pressure of 0.7 kN/m2, corresponding to 28 m/s, shall be taken as acting horizontally and normal to the sides of the bridge on the exposed area of the superstructure (calculated as in 12.2.1). and of live load taken as a single vertical plane surface having a continuous height of 22.500 m above the carriageway or.1,25 m above footway and cycle tracks, as applicable. 12.2.2.2 Railway bridges. A wind pres sure of 1.4 kN/m= (30lbf/ft2) corresponding to a wind speed of 40 m/s, shall be taken as acting horizontally and normal to the sides of the bridges on the exposed. area of the superstructure (calculated as in 12.2.1) and of live load taken as a single vertical plane surface having a continuous height of 3.75 m (12 ft) above. the rail. 12.3

For longitudinal effect A longitudinal wind force shall be combined with a corresponding lateral wind force equal to half the total lateral force given in 1.2.2 and the two shall be distributed compatibly. The longitudinal wind forces shall be determined as follows: (1) For plate girder bridges: a quarter of the total lateral wind forces on the super structure in the unloaded condition (see 12.2.1) or a quarter of the total


lateral wind forces on the superstructure and half the total lateral wind forces on the live load,in the loaded condition (see 12.2.2). (2) For trussed girder bridges: half the total lateral wind forces on the superstructure in the unloaded condition (see 12.2.1); or, half the total lateral wind forces on the superstructure and live load, in the loaded condition (see 12.2.2). 12.4 For maximum overturning effect On the bridge and its supports, the following shall be taken into account : (1) In addition to the lateral and longitudinal wind forces specified above, an upward vertical pressure of . 0.24 kN/ml acting over the net exposed area of the bridge in plan. (2) In considering the overturning effect due to wind on live load, the live load shall consist of standard loading or of unloaded wagons or vehicles of the lightest tare, whichever produces the maximum overturning effects. The latter shall be taken as not greater than 12 kN per linear metre of bridge for railway bridges and not greatet than 6 kN per linear metre of bridge for highway bridges. 13. Temperature effect Allowances shall be made for the forces resulting from the following conditions: (1) Any portion of the superstructure being restrained from moving Page 79



BS 153: Part 3A: 1972 when subjected to variations of temperature. For this purpose in Great Britain a minimum of -7 ° C and a maximum between 27 ° C and 49 ° C, depending on the location of the structure, shall be taken. Elsewhere the temperature limits shall be based on local conditions. (2) Any portion of the superstructure being at a temperature different from the rest of the structure, due to the effect of sun and shade. For this purpose the maximum difference of temperature shall be taken as 8 ° C. In determining forces and movements due to change of temperature the coefficient of expansion of steel shall be taken as 1.17 x 10-5 per ° C. 14. Frictional resistance of. expansion bearings For expansion and contraction of the structure due to variations of temperature or to other causes, the forces due to friction on the expansion bearings under dead load only shall be taken into account and the following coefficients of friction shall be used: For roller bearings with 1 or 2 rollers - 0.01 For roller bearings with 3 or more rollers - 0.05 For sliding of steel on hard copper alloy bearing - 0.15 For sliding of steel on cast iron or steel -0.25 15. Forces on parapets 15.1 Footbridge parapets . Consideration shall be given to the strength and stability of parapets. Cawangan Jalan, Ibu Pejabat JKR, K.L

Parapets may be subject to horizontal loads acting at a height of 1.00 m above the level of the footway, ranging from 0.7 kN per metre to 1.4 kN per metre, according to circumstances. The maximum load will only be encountered in extreme cases of crowd loading. The value of the loading shall be taken at the discretion of the engineer'. 15.2 Motorway and other highway bridge parapets Reference should be made to the Ministry of Transport memorandum on the subject. 16. Combination of forces The following combinations of forces shall be considered: (1) The worst combination possible of dead load with live load, impact, lurching and centrifugal force. When a member whose primary function is to resist longitudinal and nosing forces due to live load is under consideration the term live load shall include these forces. (2) The worst combination possible of any or all of the'forces listed under (1).to (11) inclusive in 2. (3) The worst combination possible of forces during erection: . (4) The worst combination possible of any or all of the forces listed in 2, at the discretion of the engineer. 17. Erection forces and effects The weight of all permanent and temporary material, together with all other forces and effects which can operate , or. any part of the structure during erection, shall be taken into account.

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BS 153: Part 3A: 1972 18. Anchorage . The stability of the structure and its parts shall be investigated and weight or anchorage shall be provided so that the least restoring moment, including anchorage, is not less than the sum of: 1.1 x dead load overturning moment, and 1.4 x overturning moments due to applied loads. Account shall be taken of possible variations of dead load for repair or other temporary purposes to ensure stability at all times. This margin of stability ifs so far as stresses are concerned shall be deemed to be covered in respect of.all parts. of the structure which have been designed for their working loads to the permissible stresses in this British Standard. In complying with the requirements of this clause it. is necessary to ascertain that the resulting pressures and shears deemed to be communicated by the bearings to the substructure will not produce failure. 19. Clauses to be referred to the engineer The following clauses in Part 3A contain points on which the decision of the engineer is required and concerning which information-is to be supplied at the time of inviting tenders. Clauses 4.1.1, 6, 7, 8, 9, 11(2), 12.1, 13(1), 15,16(4).

Appendix A Standard highway loading A.1 Type HA loading Type HA loading consists of (1) and (2), or (3), viz.: (1) A uniformly distributed lane loading. The values for this load per linear metre Cawangan Jalan, Ibu Pejabat JKR, K.L

of traffic lane are given in Table I and Fig. 1. (2) One knife edge load uniformly distributed across the width of the traffic lane. The values of this load, which shall be applied in accordance with A.3.I, are given in Fig. 1. (3) Two wheel loads each 112 kN force in line transversely to the direction of traffic flow spaced at 0.90 m centres and having a contact area of 375 mm x 75 mm, the smaller dimension being in the direction of travel, to be used in the following cases: a. Where the member supports a small area of roadway,such that it may be called on to carry the weight of one or two wheels, and where the proportion of distributed load and knife edge load which would be allocated to it is small and on cantilever projections not exceeding 1.80 m. b. Where deck slabs are designed as supported on all four sides and the distance between supports in one direction is less than twice the distance in the other direction. In this respect the edge stiffening of slabs as required by A.3.9 of this appendix shall not be deemed as providing adequate support for this purpose. A.2 Varied intensities of type HA loading

.

Where a different intensity of loading is required, Type HA loading may be varied proportionately, each item of the loading being varied pro rata. When making any reduction it should be borne in mind that an impact allowance of 25 % as specified in A.5.1 has been taken into account in this loading. This allowance is considered adequate for conditions in Great Britain, but may not necessarily be sufficient elsewhere.

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BS 153: Part 3A: 1972 A.3 Application of type HA loading A.3.1 The knife edge load shall be taken as acting as follows: A.3.1.1 On reinforced concrete slabs effectively supported on two sides and on cantilever slabs exceeding 1.80 m. In a direction parallel to the supporting members. A.3.1.2 On longitudinal girders, stringers, etc. In. a direction at right angles to the member. A.3.1.3 On cross members, including transverse cantilever girders. In a direction in line with the member. A.3.2 Where longitudinal members are spaced at less than half the width of the lane the loading to be taken on these members shall be that appropriate to a half lane width. A.3.3 The total end live load shear on any longitudinal beam shall be taken as not less than.90 kN per metre width of carriageway supported by the member. A.3.4 No allowance shall be made for impact or dispersal of load in respect of the distributed load or knife edge load. A.3.5 No allowance shall be made for impact under the wheel loads. A.3.6 Dispersal under the wheel loads, where it can occur, shall be taken at 45°. A.3.7 It shall be permissible in considering the effects of the 112 kN loads to allow a 25 90 overstress. A.18 Reinforced concrete slabs shall bedesigned on the basis of 1 m wide strips carrying one-third of the appropriate lane loading as given in Table- I and Fig. 1 except when using the wheel loads A.1(3).


Distribution reinforcement transverse to the span of the slab shall be provided throughout. For spans not exceeding 6.00 m its amount in the area of sagging moment shall be sufficient to resist not less than 5090 of the maximum dive load moment at the sections considered and it shall be so placed as to ensure effective resistance to transverse bending. A.3.9 Where the wheels of vehicles using the bridge can travel on or near the unsupported edge parallel to the main reinforcement of slab decks, edge stiffening or its equivalent shall be provided capable of carrying live load as described below, in addition to the live load which would normally be allocated to it. A.3.9.1 Longitudinal slabs. That proportion of loading from Fig. 1 and Table 1 appropriate to a strip of slab having a width equal to onequarter of the span, but not more than 1.50 m nor less than 0.60 m. Alternatively, the slab may be extended beyond the edge of the carriageway for a distance equal to one-quarter of the span, but not more than 1.50 m nor less than 0.60 m. A.3.9.2 Transverse slabs. That proportion of loading from Fig. 1 and Table 1 appropriate to a strip having a width equal to two-thirds of the span. A.3.10 Where elements of a structure. can sustain the effects of live load in 'two ways, i.e., as elements in themselves and also as parts of the structure (as, e.g., the top flange of a box girder functioning as a deck plate), the elements shall be designed to resist the sum of the effects of the appropriate loading for each condition. Where the wheel loads of A.1(3) are used, the 25 % overstress permitted in A.3.7 shall be applied in considering the sum of the effects.

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Table 1. Highway loading. Type HA Equivalent uniformly distributed load (U.D.L) to be used in conjunction with the knife edge load (see Fig. 1)

Loaded Length

U.D.L for U.D.L for beams per longitudinal metre of lane slabs per metre of lane

U.D.L for Loaded transverse length slabs and cross girders per metre of lane

U.D.L for U.D.L for beams per longitudinal metre of lane slabs per metre of lane

U.D.L for transverse slabs and coss girders per metre of lane.

m 1.00 1.25 1.50 1.75

kN 318.6 233.7 179.4 146.4

kN 318.6 233.7 179.4 139.5

kN 282 153.6 113.4 89.4

m 4.00 4.25 4.50 4.75

kN 64.8 60.9 57.0 52.8

kN 42 39.0 36.3 35.1

kN 34.2 33.0 31.8 31.5

2.00 2.25 2.50 2.75

126.6 112.8 101.7 92.4

107.1 85.5 72.0 64.5

72.6 62.7 55.2 48.6

5.00 5.50 6.00 6.50-23.0

49.2 41.1 33.0 31.5

33.9 32.1 31.5 31.5

31.5 31.5 31.5 31.5

3.00 3.25 3.50 3.75

84.6 77.4 72.3 68.4

58.5 53.4 49.2 45.3

45.0 41.7 37.7 36.3


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Loaded length

Force

Loaded length

Force

Loaded length

Force

Loaded length

Force

m 24.0 25.0 26.0 27.0

kN/m 31.2 30.8 30.4 30.0

m 52.0 53.0 54.0 55.0

kN/m 22.3 22.0 21.8 21.5

m 80.0 82.0 84.0 86.0

kN/m 17.7 17.4 17.2 17.0

m 220 240 260 280

kN/m 12.2 11.7 11.3 10.9

28.0 29.0 30.0 31.0

29.0 29.3 28.9 28.5

56.0 57.0 58.0 59.0

21.3 21.1 20.9 20.7

88.0 90.0 92.0 94.0

16.8 16.6 16.4 16.2

300 325 350 375

10.6 10.1 9.8 9.5

32.0 33.0 34.0 35.0

28.2 27.8 27.4 27.0

60.0 61.0 62.0 63.0

20.6 20.4 20.2 20.0

96.0 98.0 100 105

16.1 16.0 15.9 15.6

400 425 450 475

9.0 8.6 8.4 8.2

36.0 37.0 38.0 39.0

26.8 26.6 26.2 26.0

64.0 65.0 66.0 67.0

19.8 19.7 19.6 19.4

110 115 120 125

15.3 15.12 14.9 14.7

500 525 550 575

7.9 7.7 7.4 7.3

40.0 41.0 42.0 43.0

25.7 25.4 25.2 24.9

68.0 69.0 70.0 71.0

19.3 19.1 19.0 18.9

130 135 140 145

14.5 14.3 14.1 14.0

600 625 650 675

7.1 7.0 6.8 6.7

44.0 45.0 46.0 47.0

24.6 24.3 24.0 23.8

72.0 73.0 74.0 75.0

18.7 18.6 18.5 18.3

150 155 160 165

13.8 13.7 13.6 13.5

700 725 750 775

6.6 6.5 6.4 6.3

48.0 49.0 50.0 51.0

23.5 23.2 22.9 22.6

76.0 77.0 78.0 79.0

18.2 18.1 17.9 17.8

170 180 190 200

13.4 13.1 12.9 12.7

800 850 900

6.1 5.9 5.8

Note to Table t and Fig. i Normal loading (Type HA) approximately, represents the effect of three vehicles, each 22 tonne (220 kN) in weight, closely spaced, in each of two carriageway lanes, followed by 10 tonne (I00 kN) and 5 tonne (50 kN) vehicles. Design loads for short span members to allow for possible local concentration of loads, the effect of two 90 kN wheel forces 0.90 m apart have been considered (i.e. approximately two 112 kN wheel forces with 25 % overstress). In general, normal loading is sufficient to cover 30 units of abnormal loading (Type HB) for loaded lengths above 30.0 m and for slabs (but see A.5), and at least 20 units of abnormal loading for beams having spans less than 30.0 m carrying decks with a weight similar to that of an ordinary reinforced concrete slab. Where a bridge is definitely required to carry abnormal loads in excess of 20 units a check should be made. A special case is a narrow bridge or one in which the carriageway is cantilevered beyond the beams, where high stresses car. occur under abnormal loading.


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BS 153: Part 3A: 1972 A.4- Type HB loading Type HB loading is a unit loading representing a single abnormally heavy vehicle. Figure 2 shows the plan and axle arrangement for one unit this loading. The weight factora for each of the four axles shall each be multiplied by an appropriate number of units. All parts of the btidge shall be capable of carrying Type HA loading, and shall be increased in strength, where necessary so as to be able to carry Type HB loading as an alternative.

A.5.4 Suitable provision shall be made for the dispersion (at 45 °} or distribution of the wheel loads where these can take place. . A.5.5 Members which occur in such a position that they may be straddled by two axles or wheels of Type HB loading may, if desired, be designed by simple statical methods, subject to a reduction factor obtained from the following table where the bridge deck is designed to possess sufficient rigidity to admit of reasonable transverse distribution. The reduction can be applied td jack arch decks.

A.5 Application of type- HB loading. A.5.1 No allowance for impact shall be made.: A.5.2 t shah be permissible in considering the effects of this loading to allow 25 % overstress (but see 4 in Part 38 for total permissible stress). A.5.3 The contact area of the heaviest wheel shall be taken as 375 mm x 75 mm the smaller dimension being taken in the direction of travel.


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Spacing of member

Reduction factor

mm 250 500 750 1000 1250

Spacing of members

Reduction factor

mm 0.66 0.68 0.70 0.73 0.77

1500 1750 2000 2150

0.81 0.88 0.96 1.00




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CHAPTER4 DECK. SLAB

2.0 Pigeaud's Method

DESIGN OF DECK SLAB 1.0 Introduction. 2.0 Pigeaud’s Method: 2.1 Application of Pigeaud's Method. 3.0 Westergaard+s Method. 3.1 Effect of encastre. 3.2 Application of Westergaard's Method. 1.0 Introduction In addition to the distribution of the load in the main longitudinal beams and the tranverse diaphragm beam, there will also be a local stress distribution in the deck slab. This local stress distribution is due to: A) Dead load of deck slab and surfacing. B) HA Loading. C) HB wheel loads. This stress distribution will, in general, be restricted to. the deck slab but may be superimposed to give the resultant stress distribution in the bridge as a whole. The boundary conditions of the deck slab are complex since the longitudinal and the tranverse beams do not deflect equally. The problem can be simplified by assuming.that the boundaries of the deck slab are simple and undeflecting. A factor is then introduced to take account of,the continuity over the supports. The determination of stress due to uniform loading, i.e dead load and HA load, is quite straight forward and methods described in CP 114 can be employed. For stress due to wheel load, it may be determined by Pigeaud's Method or Westergaard's Method. However, Westergaard's Method is the most commonly used since the conditions in most practical bridge structure suit this method.


of the surfacing. Hence, for HB wheel of dimension 15 in x 3 in. u = 15+2t V = 3+ 2t where t is the surfacing thickness. Ratio of a/b , u/a and v/b are.then calculated. Values of M1, and M2. can then be determined from Pigeaud's Curve, where M.1 and M.2 .are functions of u/a and v/b for various values .of P = a/b equal to 1.0. 0.9 , 0.8 , 0.707 , 0.6 , 0.5 0.4 , 0.3 , 0.2 and 0. The minimum moments are then derived as follows: M= max. moment across direction a = ( M1 + 0.15 M2) P M= max. moment across direction b = ( 0.15 M1 + M 2) P . where P is,the wheel load in lbs and M and M2 in lbs in/in. Pigeaud suggested that for two central load, as shown in figure 2, the value of U and V should be taken as follows.

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Fig.2. Notation in Pigeaud's Method for two central loads. u = 3 in + 2t } For load.as in fig.2 (a). v = w + bo + 2t } and u = w + bo + 2t V = 3in + 2t 2.1

} for load as in fig.2 (b) }

Application of Pigeaud's Method.

Pigeaud's Method is most useful wh dealing with slab in which the width is less than 1.8 times t e span. To take account of fixity at the boundaries of the slab a factor of 0.8 is normally introduced. Thus the moments are derive for the simply supported slab and multiplied by 0.8 to give the approximate moment for the boundries. Some limitations of Pigeaud's Method are as follows: i)Only central load can be dealt with. ii)When dealing with 2 loads, it is not sufficiently accurate to replace the loads by a single load having an area which is dependant on the spacing. iii) It is not very easy to read accu rately the values of. MI and M2 from Pigeaud's Curve.

3.0 Westergaard's Method The notation adopted by Westergaard is as shown.

Fig.3. Westergaard's Notation. The initial assumption is that the slab extends sufficiently far in the direction + y without being supported. by dia~ragms for it to be considered as an infinite slab Poison's ratio was taken as 0.15.


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REFERENCE' R.E. Rowe,, Concrete Bridge Design/Applied Science Publishers LTD


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CHAPTER

5

BRIDGE BEARING, DOWEL BAR AND EXPANSION JOINT BEARINGS IN BRIDGES 1.0 DESIGN CODE (CONCERNING ELASTOMERIC BEARINGS) Department of the Environment Highway Directorate Technical Memorandum (Bridges) No. BE 1/76 2.0 FUNCTIONS OF BEARINGS i) To trgnsfer loads from superstructure to substructure. ii) To accomodate expansion and contraction movements between different parts of a .structure. iii)To accomodate q nd rotations of deck girders. Rotation occurs as the deck deflects under load. iv)To limit the forces actually transmitted to the substructures by suitable design. v) To damp down vibrations and minimise the effect of impact loading in case of elastomeric bearings. 3.0 SOURCES OF DISPLACEI%ENTS 3.1 Movement and rotations tend to occur in all types of structural members. In bridges, these are generated due to the following reasons: I) Temperature variations ii) Concrete shrinkage and creep iii) Effect of prestressing iv)Dead, superimposed and live loads v) Tilt, settlements and seismic disturbances Displacements can either be in the form of movement in the longitudinal, transverse and vertical directions, rotational modes or any of their combinations. 3:2 For the purpose of,designing elastomeric bearings, it is the practice of Unit Jambatan to consider displacements only due to the Cawangan Jalan, Ibu Pejabat JKR, K.L

following factors: i) Longitudinal movements due to temperature variation, creep and shrinkage of concrete (S.T.C effects). ii) Rotation of girders due to the effect of dead, superimposed and live loads. 4.0 TYPES OF BEARINGS Basically, there are three different types of bearings commonly used in structural engineering. They are categorised according to material Classification as follows : i) Elastomeric Bearing. An.elastomer is either vulcanised natural rubber or synthetic material-called neoprene having rubberlike characteristics. Movement and rotation are accommodated by compressing or shearing .the layers. ii) Mechanical Bearing. The bearings are made up of metal such as steel. Movement and rotation are accommodated by rolling, rocking or sliding action of the metal parts. iii) Combination of Elastomeric and Mechanical Parts..-For bearings in this category, elastomer is used as the rotation medium'while horizontal movement capacity is.provided mechanically.

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5.0 INITIAL SELECTION OF BEARINGS Many small bridges need no formal bearings. In general, this is true for spans below 10m, except where vibration is involved. In situation where bearings are required, they are designed and supplied by a specialist company. The criteria for the initial selection of bearings shall be based upon the following data : CHARACTERISTIC

Vertical load capacity (KN) Horizontal load capacity (KN) Horizontal movement (mm) Rotatian about horizontal axis (rod) To resist uplist forces Vibration damping Maintenance Contact stresses under bearing system First cost Life under proper maintenance schedule (years)

6.0

6.1

PROPERTIES OF ELASTOMER Elastomers can be produced with a wide range of physical properties. Some of the important properties include hardness, elastic, shear and bulk modulus which form part of the design parameters.

ELASTOMERIC

MECHANICAL

3000 20 70

over 30,000 over 3000 Virtually unlimited 0.08 possible improbable required higher higher 100-120

0.02 improbable possible negligible lower lower 45-80

ELASTOMERIC BEARING i Basically all the bearings being designed and adopted by Unit Jambatan are of,the elastomeric type. This is so due to the fact that the majority of bridges are subjected to-loadings and rotations which are within the capacity of elastomeric bearings. For the purpose of this design manual, only elastomeric bearing will be discussed.


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The properties that formed the des4.gn parameters are as -tabulated below : TABLE 1 (ELASTIC CONSTANT)

Hardness (IRHD)

45 50 55 60 65

Young’s Modulus, E (N/mm2)

Shear Modulus G (N/mm2)

1.80 2.20 3.25 4.45 5.85

0.54 0.64 0.81 1.06 1.37

IRHD denotes International Rubber Hardness whose scale extends from 0 (very soft) to 100 (very hard). K is an empirically determined constant. 6.2

THREE TYPES OF ELASTOMERIC BEARINGS i) A laminated bearing consists of one or more elastomer slabs bonded to metal plates so as to form a sandwich. ii) A bearing pad is a single unreinforced elastomer slab. iii) A bearing strip is a continuous bearing pad for which B/L is greater than 5.

6.3

K Constant

Buld Modulus, E (N/mm2)

0.8 0.73 0.64 0.57 0.54

2000 2000 2000 2000 2000

Elongation at Break, Xe (%) 600 600 600 450 400

iii) The thickness of bearing pads and strips shall be not less than 10mm nor greater than 25mm. (Not counting inner rubber slabs of laminated bearings). iv)The thickness of the steel plate reinforcement shall be not less than 2(t1 + t2.,) V, but the thickness shall -------------A1.fs be not less than 3mm for outer plates and not less than 1.5mm for internal plates. A greater thickness of

BASIC ASSUMPTIONS IN DESIGN i) The elastomer is an elastic and almost incompressible material; its bulk modulus has to be taken into account where appropriate. ii) There is no relative movement between elastomer and reinforcement plate at an interface.


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ii) Rotational Capacity of bearing shall be equal to or greater than rotation of girder at support. An additional tolerance of 0.005 radian shall be added to the rotation of girders to cater for the seating allowance. iii) Factors on stability of bearing. iv) Friction location.This is to ascertain that the bearing will not be displaced from the original position during service. 6.6 STATIC BEHAVIOUR OF ELASTOMER UNDER COMPRESSION When a block of elastomer is loaded in compression, its vertical stiffeness depends upon its freedom to bulge at the sides. This is expressed in terms of the ‘shape factor’.

On the same plan area, a thinner block will be stiffer vertically. ii) Partial Slippage. Under compressive loading, partial slip page will occur to the unbonded layers of an elastomeric bearing. Thus, the vertical stiffeness of the unbonded layers are reduced. To compensate for this, the two outer layers of a laminated bearing is treated as being 40% greater than the actual thickness. For the inner layers, since they are bonded on both sides by the steel plates, the effective thickness is equal to the actual thickness. For pad and strip bearings, their thickness is treated as being 80% greater than the actual thickness

The shape factor depends on the dimensions ans shapes of the elastomer slab. The Vertical stiffeness of the block increases rapidly with the shape factor. Cawangan Jalan, Ibu Pejabat JKR, K.L

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7.0


LOCATION OF BEARING BY FRICTION When a bearing is subjected to direct shear strain, horizontal force is induced which tends to displace the bearing from its original position. To prevent this happening, there must be sufficient minimum vertical load acting on the bearing. Assuming the coefficient of friction between elastomer and concrete seating of 0.33 and a coefficient of 0.25 with steel seating, the friction location is checked as follow :

Minimum Compressive Force, V min. ----------------------------------------------- > 3 for elastomer in contact Maximum Horizontal Force, H max with concrete (> 4 for steel contact) V min = Dead Load Alone H Max = Ao G e b

7.1 DESIGN EXAMPLE The bridge designer can either select proprietory elastomeric bearings, or design bearings in detail, or even simply specify the requisite loads, movements and rotations, and then approve the bearing details submitted by the contractor. Standard. proprietory bearings, even if not fully loaded, will prove to be cheaper than special designs. The design of elastomeric bearings is essentially a trial and error process. The plan size of a bearing is normally governed by the. width of the beam it supports and the width of the abutment seating in the direction of the bridge span.

Note The rotation of the beam shall include an additional tolerance of 0.005 radians to.cater for the seating allowgnce. Thus, the minimum rotational capacity of the bearing shall.be 0.006 and 0.008 radians respectively under HA and HB loadings.

An elastomeric bearing shall now be designed to satisfy the following requirements:-


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The carrying capacity of a free P nd bearing, subjected to horizontal movement, can be taken to be about 0.8 S N/mm2, as a first guess. Normally,, laminating is required in order to provide sufficient horizontal movement, while maintaining the vertical load carrying capacity. Plain.pad.may be sufficient if horizontal movement is very small, but not in this case. Horizontal movement of about half the total thickness of elastomer can be used as a starting point in design.


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DESIGN OF DOWEL BARS 1) Elastomeric bearing can he conveniently subdivided into two types 'fixed', where the support member can only rotate, all horizontal movements. being restrained, and 'free', where the member can rctate and also move horizontally. 2) The fixed state is provided by dowels passing from the beam. to its support. In order to make provision for the possible replacement of bearings, these dowels are best placed between bearings, but where space is restricted they car. pass through holes in the bearing. Dowels usually need an elastomeric cap at one end to permit the superstructure to rotate relative to the sub structure. The dowels must penetrate to sufficient depth to resist the horizontal load, without inducing excessive stresses in the concrete. In all cases the doi,lels should be long enough to reach the main reinforcement in the support.

(Note: The load due to S.T.C is such that F- Z A,G eb,) 5) TYPICAL CALCULATION A) Design suibtable dowel bars at the fixed end of a bridge span to transfer the horizontal forces to the abutment. Input datas are as follwos :

3) Dowel bars at one end of a bridge span will form an expansion centre line, longitudinal movements of the deck will be accomodated by the bearings at the free end, horizontal loads will be carried by the dowels. It should be remembered that horizontal forces will be transmitted to the support at the tree end, due to the resistance of the bearings there to the horizontal movements, and this same force will be transmitted through the superstructure to the fixed end dowels. In Unit Jambatan,this force is calculated on the basis of the movement of the deck due /to changes in temperature, shrinkage and creep of concrete ( S.T.C ). 4) The dowel bars shall be designed to resist a combination of three types of horizontal load as follows: (i) Tractive load (ii) Wind load. (iii)Load due to the effect of S.T.C above.


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EXPANSION JOINTS 1) GENERAL The expansion joint is an integral part of any bridge structure and should be considered at an early stage in the design. Joints which are properly designed, installed by specialist operatives together with reasonable maintenance should give trouble free service within its lifespan. Expansion joint is situated in the most vulnerable position on the bridge deck where it is subjected to impact.loading, vibration and exposed to dirt, ozone attack and other corrosive chemicals. 2) FUNCTIONAL REQUIREMENTS . These are as follows i) To accommodate movements and with stand loadings. ii) To cater for operational needs. The sources of movements to be accommodated by an expansion joint are identical to that of a bearing.For this reason, expansion joints and bearings of any particular span of a bridge shall be designed to be compatible. An expansion joint shall be designed to withstand a combination of vertical and horizontal loads. This shall be discussed later under the heading of design load. The operational requirements for joints are as follows i)Possess good riding characteristics. ii) Not a skid hazard or danger. iii) Silent and vibration free iv) Be sealed against1water and foreign matter or make provision for their disposal. v) Be capable of absorbing the various types and ranges of movement., without being extruded or expelled from position. vi) Riding surface of joint must be able to withstand wear and tear and be durable against petroleum product, weather, etc.


vii) Facilities easy inspection, maintenance and repair 4) CLASSIFICATION OF EXPANSION JOINTS. i) Open Gap Joint. The joint comprises of two edges which are spaced some distance apart and not interconnected by. any load supporting connection. There are two categories of open gap joint : a) Buried joint under continuous premix surfacing. Most of the expansion joints being adopted by Unit Jambatan fall under this category. b)Exposed joints which are installed to flush with the wearing surface of the bridge deck. The joint may be completely opened or be sealed up with, say, neoprene sealing element. ii) Covered Gap Joint ( or Bridged Joint ). The gap is bridged by a sliding plate or some other transverse structural element. The structural element will be subjected to a combination of vertical and horizontal loads. iii) Composite Expansion Joint. The joint comprises of a gap bridging element for carrying the traffic loads together with a deformable closing seal element to ensure continuity of the carriageway surface.

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5) SELECTION OF JOINT TYPE This is largely determined by the total range.of movement to be expected. 6) DESIGN CONSIDERATIONS . Expansion gap should be straight of uniform width and have a minimum gap of 6mm at maximum temperature. 7) DESIGN LOAD a) Vertical Two 112 KN wheel loads, 0.9m apart, with a contact area of 265 x 265mm. It shall be applied to the edge ef.the expansion gap. It.may be spread tranversely over such a length as is justified by the continuity and rigidity of the joint subject to a maximum of 450mm on either side of the centre line of each wheel. b) Horizontal A traffic force of 60KN/m run o£ joint, acting at load level.. 8) ANCHORAGE SYSTEM i) The joints are severely loaded. Forces involved are vertical, horizontal together with twisting moments. ii) The common types of anchorage system: . - Epoxy mortar nosing. - Anchor bars. - Holding down bolts ( May be prestressed ). iii) Stresses in concrete, structural steel, epoxy mortar etc must be within the permissible values. 9) INSTALLATION OF EXPANSION JOINT i) The whole operation shall receive competent supervision. Only.proper materials and equipment shall be used, in accordancewith the manufacturers instructions. ii) Prior to installing the joint system, the bedding shall be prepared accordingly without traces of dirt, oil and other impurities. iii) Composite meoprene expansion Cawangan Jalan, Ibu Pejabat JKR, K.L

joints are installed in precompressed condition: - During placing+fconcrete or epoxy mortar, the joint assembly shall be immovable both in vertical and horizontal directions. - Can be achieved by :a) Clamp down the joint assembly. b) Install under uniform temperature condition. iv) The joint shall hot be subjected to any kind of loading until /all the materials have gained the required strength. 10) PROVISION FOR DRAINAGE Water and other foreign products shall not be allowed to reach the bearings, girders, pier head etc, Provision must be made to prevent the ingress of surface water through the joint. i) For water tight joints, ensure that the sealing agents are performing in the manner intended. ii) For large open joints, Special drainage techniques must be adopted to deal with surface water, earth etc, easy access for cleaning shall be provided. iii) Provide with proper Camber and crossfall within the carriageway surface around the joint to discharge water. v) Water that collects and runs along the kerbs sould be intercepted by suitable drainage outlet before it reaches the joints 11) MAINTENANCE It is essential that expansion joints are easily accessible for the purpose of maintenance. i) Joints shall be regularly inspected to ensure that no parts are loose, the sealing materials are intact, and drainage systems are working properly. ii) Safeguard the screws and bolts against corrosion. Holding down bolts need to be retentioned to the required torque once they are.loose. Page 121



iii) Ensure that no debris are left to accumulate in the joint gape This will induce enormous restraining forces causing damaging effects. iv) The road surface should be maintained to the level of the joint and in no case should the difference in level become more than 6mm. References. 1. Department of the Environment Highways Directorate. Technical Memorandum B.E. 1/76. Design Requirements For Elastomeric Bridge Bearings. 2. Bearings in Structural Engineering. J.E. Long M. Sc. M.I.C.E., M.I. Structural Engineering. Newnes - Butterworths, London. (1974) 3. The Theory and Practice of Bearings and Expansion Joints For Bridges. David J. Lee B. Sc. Tech, DIC, C. Eng., FILE, FI Struct. E. Cement & }Concrete Association (1971) 4.

Expansion Joints in Bridges and Concrete Roads. - W. Koster. Maclaren & Sons, London..

5.

Department of the Environment Highways Directorate. Technical Memorandum BE 3/72. Design Requirement for Expansion Joints.


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Bridge Design

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