Design Basis r0

AL HATMY ENGINEERING CONSULTANCY CONSULTANCY LLC

PROPOSED SULTAN QABOOS MOSQUE AT SOHAR

Structural Design Basis Report

REV: 0 JANUARY 2012

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Table of Contents

1.

2.

Introduction .........................................................................................................................................

3

1.1

General ........................................................................................................................................

3

1.2

Related documents...................................................................................................................... documents......................................................................................................................

3

1.3

Scope of work of work ..............................................................................................................................

3

1.4.

Consultant’s Design and Calculation Documentation ................................................................. 3

Design Criteria ......................................................................................................................................

5

2.1

Ranking ........................................................................................................................................

5

2.2

Basis of design of design .............................................................................................................................

5

2.3

Codes and standards ...................................................................................................................

5

2.4

Service life of building of building structures ................................................................................................

6

3. Design requirements, loads and load combinations ................................................................................

7

3.1

Introduction................................................................................................................................. Introduction .................................................................................................................................

7

3.2

Definition of loads of loads .......................................................................................................................

7

3.3

Dead load..................................................................................................................................... load .....................................................................................................................................

8

3.4

Imposed loads, live loads............................................................................................................. loads.............................................................................................................

9

3.5

Wind load ....................................................................................................................................

9

3.6

Temperature loads ....................................................................................................................

10

3.7

Sand accumulation ....................................................................................................................

10

3.8

Water accumulation ..................................................................................................................

10

3.9

Earth and water pressure .............................................................................................................

10

3.10

Creep and shrinkage of concrete of concrete............................................................................................... ...............................................................................................

11

3.11

Earthquake load......................................................................................................................... load .........................................................................................................................

11

3.12

Accidental load

13













4.

5.

6.

3.14

General robustness / disproportionate collapse....................................................................... collapse ....................................................................... 14

3.15

Comfort requirements............................................................................................................... requirements...............................................................................................................

14

3.16

Deflection requirements ...........................................................................................................

14

3.18

Load Combinations ....................................................................................................................

16

3.19

Primary and secondary structures............................................................................................. structures.............................................................................................

19

Materials ............................................................................................................................................

20

4.1

Reinforced concrete ..................................................................................................................

20

4.2

Structural Steel ..........................................................................................................................

21

4.3

Composite structures ................................................................................................................

23

4.4

Block work .................................................................................................................................

24

Geotechnical conditions and parameters ..........................................................................................

25

5.1

Bearing capacity ........................................................................................................................

25

5.2

Safety factors............................................................................................................................. factors .............................................................................................................................

25

5.3

Piles............................................................................................................................................ Piles............................................................................................................................................

25

5.4

Settlements ...............................................................................................................................

25

Joints ..................................................................................................................................................

26

6.1

General ......................................................................................................................................

26

6.2

Movement Joints .......................................................................................................................

26

Appendix A – MODES Wind Speed and Seismic Zone Charts ..................................................................... 29 Appendix B - Concrete service life design parameters ...............................................................................

29

Appendix C - Norms and standards ............................................................................................................

30













1.

Introduction

1.1

General

The intent of this document is to outline the minimum design requirements for the structural design of the building structures. This Design Basis covers permanent structures only. Temporary structures, e.g. for erection purposes, shall be based on the same set of codes and standards as referred to in this Design Basis.

1.2

Related documents

The documents mentioned above the Design Basis shall also be read in conjunction with the building specific Performance Specifications, the geotechnical reports, and concourse as well as the structural drawings.

1.3

Scope of work

The following building structures are covered by this Design Basis. •

Proposed Sultan Qaboos Mosque at Sohar

1.4. Consultant’s Design and Calculation Documentation 1.4.1 General

This section describes the requirements of Design and Calculation Documentation and to the software packages used for the design. The requirements given shall be considered as the minimum requirements and shall always be included for all structural elements and buildings. The requirements apply to the design of both temporary and permanent structures. The requirements can however in specific cases be reduced if approved by the Engineer in advance. The requirements for drawings prepared by the consultant/contractor are given in the General Contract Requirements and the General Specifications for Concrete Work, Masonry and Steelwork. All drawings and calculation documentation prepared by the Consultan/Contractor shall follow an approved QA procedure before submittal to the Engineer in accordance with the General Contract Requirements.













1.4.2

Standard contents of structural design calculations

The calculation documentation shall as a minimum include the following for every calculation submitted: 1. 2. 3. 4. 5. 6. 7. 8.

9. 10. 11

12 13

14 15

Introduction Conclusion / Summary including statement of adherence to this Design Basis Reference to drawings Description of the overall structural system including sketches or diagrams depicting the structural system Description of geometry including cross-sections and cross-sectional constants for the members used Description of material properties, e.g. E-modulus, density, etc. Description of applied loads Relevant input data from FEM-software including sketches/figures showing support locations and types, loads, dimensions, member properties etc. (if used) Relevant output from FEM-software (if used) Check of FEM results (if used) Design of structural elements, i.e. check of stresses, deflections, vibrations, stability etc. See below mandatory detailed content of every structural item to be designed. Design of connections, i.e. welds, bolts, gusset plates, stiffeners, etc. Calculation of support reactions, evaluation of geotechnical design support reactions, evaluation of geotechnical design parameters based on data reports and design of foundations. See below mandatory detailed content of every structural item to be designed. Soft copy of FE-models List of reference documents

Example of design of a concrete beam: •

Reference to beam number and other info to locate beam.

•

Sketch or illustration which explains where this beam is located

•

Sketch or illustration of the static system of which this beam is a part.

•

•

Clear reference to the beam and node number, name of model, and load case from which the design section forces are taken Clear explanation of which load case is governing (ULS, SLS, ALS) and explanation of how the design section forces have been selected













1.4.3

Software requirements

Software packages e.g. FE-programmes, excel sheets for design of structural elements (e.g. RC beams, columns) used in the design shall be in accordance with the requirements given in the General Contract Requirements. FE-model software packages shall be internationally recognised, e.g. Staad Pro, Robot, ETABS, GT Strudl, SAP2000, Lusas. The Consultant shall advise which software packages including versions that will be used for the design at least 8 weeks before the documentation is submitted.

2.

Design Criteria

2.1

Ranking

This document, codes, standards and recommendations shall be ranked as follows: 1. Design basis 2. British Standard, Codes of Practice 3. Uniform Building Code 1997 (UBC 1997) 4. Recommendations

In case the detailing required by the UBC 1997 due to earthquake is more onerous than that required by the British Standards, then the UBC 1997 shall take precedence over the British Standards. In case of doubt the Consultant shall follow the Engineer’s decision.

2.2

Basis of design

The Employer’s Requirements, comprising Engineer’s Drawings, General Specifications and building specific Performance Specifications, shall form the basis for the Consultant’s structural calculations and detailed design drawings. The Consultant’s structural detailed design drawings shall be coordinated with all other disciplines.

2.3

Codes and standards

The structural design shall be based on British Standard Codes of Practice as required by this Design Basis. Refer to appendix C for a list of the codes and standards referred to in this document. Seismic design of buildings shall be based on the 1997 Uniform Building Code.















2.4

Service life of building structures

The term “service life” shall be understood as the time when major repairs will have to take place in order to ensure the continuous use of the building. The normal service life of all primary structural elements in all buildings shall 50 years. In order to achieve the required service life for buildings a systematic durability design procedure shall be adopted. A description of the approach for concrete structures is given below. 2.4.1

Durability of concrete structures

The primary approach to designing concrete elements for durability is based on the primary durability barriers against chloride ingress such as a high quality and relatively impermeable concrete (i.e. a concrete with low chloride diffusivity) and sufficient concrete cover. The General Specification for Concrete Work also follows this approach. All concrete surfaces located above ground and exposed to atmosphere shall only be treated with surface coating if so required by the architectural finishes. Structures which are located below ground and are generally exposed to earth (and ground water) on one side (outer side) and air on the other side (inner side) shall only be treated with surface coating on the inner side if so required by the architectural finishes. Water tanks and structures below the groundwater table shall be designed to be 100% watertight and free from all leakage, seepage and damp patches. The floor and wall structures shall be provided with an external waterproofing membrane. The water tightness shall consist of the concrete itself - i.e. a dense concrete with no through-going cracks - and the membrane. The waterproof membrane shall also protect the concrete structure against chemical attack from salts in the groundwater and soil. Potential waterproofing materials for use are: •

Bonded preformed sheet membranes

•

Unbonded preformed sheet membranes (pure bentonite membranes are not permitted) Liquid (spray

brush) applied membrane













A project specific exposure designation has been introduced which differentiates between drywet (DRY-WET), atmospheric (ATM) and indoor (IND) and submerged (SUBM) conditions. The designations are defined in the following: Exposure class SUBM DRY-WET

Exposure description Concrete faces of structural parts permanently buried in the salty soil/groundwater (from approx. 1 m below lowest GWL and deeper) a) Concrete faces buried in the soil/groundwater exposed to changing groundwater levels. Cycles of wetting and drying resulting in chloride accumulation at the concrete surface or b) Internal concrete faces at water-retaining structures (one-sided water pressure) with risk of chloride accumulation due to water ingress through cracks, un-tight tie-bars, links, malfunctioning of membrane etc.

DRY

Concrete faces of structural parts buried in the soil (from approx. 1 m above highest GWL)

ATM

Concrete faces exposed expos ed to airborne chlorides

IND

Concrete faces exposed to atmospheric CO2 (no chloride load)

3. Design requirements, loads and load combinations 3.1

Introduction

This chapter describes the characteristic loads, design loads, deflection requirements and load combinations that shall be taken into account in the structural design. The loads specified in section 3.3 and 3.4 of this Design Basis have been assumed for the Preliminary Design and should be considered for information only. The Consultant shall in his Detailed Design verify that all loads apply to the current design and the chosen equipment and machinery installed in the buildings.













3.3 3.3.1

Dead load Dead load from roof, equipment etc.

The dead loads specified below are characteristic loads. Corrugated steel sheets + Kalzip or similar roof sheeting

Roofing 2 layers of bituminous membrane below the roof insulation.

0.20 - 0.35 kN/m2

placed 0.10 kN/m2

Insulation (100mm mineral wool)

0.3 kN/m2

Density of reinforced concrete members

26 kN/m3

Density of reinforced concrete members, buoyancy

24 kN/m3

Density of structural steel members

77.0 kN/m3

Services (electrical, A.C, Water, etc.) suspended from the underside of all slabs* Suspended ceiling- general

installation 0.50 kN/m2 0.25 kN/m

Floor finish, 50mm screed

1.25 kN/m2

Floor finish, 100mm screed

2.50 kN/m2

Floor finish incl. floor cooling, 150 mm screed

3.75kN/m2

Partition walls, gypsum

1.5 kN/m3

90/100mm block work wall incl. 2x20mm plaster

2.8 kN/2

140/150mm block work wall incl. 2x20mm plaster

3.8kN/m2

190/200mm block work wall incl. 2x20 mm plaster

4.8kN/m2













Loading from block work partitions shall be taken into account according to the actual positioning in the present architectural design either as appropriate as a general floor loading or as a line load unless otherwise required by the Employer’s Requirements. The loads given for gypsum partition walls and block work walls are per vertical wall area. Loads from cladding shall be included as appropriate corresponding to the specific type of cladding, e.g. stone cladding, aluminum cladding etc. 3.3.2

Concentrated loads

The structural slabs shall be designed for linear and concentrated loads from block work partitions, equipment and the like as appropriate.

3.4

Imposed loads, live loads

The total minimum imposed floor loads to be used in the structural design shall in general be in accordance with BS 6399-1. Pattern loading shall be considered as appropriate. Where a concentrated load creates a more severe load implication, this shall be included in the calculation. The live loads specified below are characteristic loads. The uniform and concentrated loads shall not be considered to act simultaneously. Area Roof (access for maintenance only)

Uniform load 0.5 kN/m2

Concentrated load 1.4 kN

Assembly areas without fixed seating

5.0 kN/m2

3.6 kN

Stairs and general corridors

4.0 kN/m2

4.0 kN

Offices and toilets

2.5 kN/m2

2.7 kN

Rooms in general

2.0 kN/m2

2.7 kN

Machinery hall

7.5 kN/m2

4.5 kN













This gives a maximum 3 second gust wind speed likely to be exceed only once in 50 years, corresponding to an annual risk of 0.02, at 10 m above the ground in open level country. The wind loads shall be determined according to BS 6399-2:1997 using the Standard method where the basic wind speed is defined as an hourly mean wind speed with an annual risk of being exceeded of 0.02 at a height of 10 m over completely flat terrain. The basic wind speed shall be taken as: 3 second gust wind speed (m/s)

Muscat

46

Salalah

50

3.6

hourly mean wind speed ( m/s)

25

Temperature loads

The effects of thermal actions on the structures due to climatic and operational temperature changes both during the construction phase and for the final structures shall be taken into account by applying temperature loads. The ambient temperature is set at 28°C. The safety factor should be taken as 1.2 in ULS and 1.0 in SLS. The temperature loads shall be incorporated in the load combinations as appropriate according to BS 8110-1 and BS 5950-1 and section 3.19.

3.7

Sand accumulation

Sand accumulation is considered not to occur, and shall therefore not be accounted for in the design.

3.8

Water accumulation















The earth pressure shall be determined as the pressure at rest.

3.10 Creep and shrinkage of concrete The effects of creep and shrinkage shall be determined according to BS EN 1992-1-1 and included in the design as appropriate. The load effects caused by creep and shrinkage of concrete in composite structures shall be determined according to BS EN 1994-1-1 and BS EN 19921-1 and included in the design as appropriate. The safety factor shall be taken as 1.2 in ULS and 1.0 in SLS.

3.11 Earthquake load The Uniform Building Code 1997 (UBC 1997) identifies the Muscat area as having a seismic risk to that of zone 2A. The structural design shall therefore be based on the strength recommendations for zone 2A. Earthquake load calculations shall be in accordance with UBC 1997 and be based on the following parameters. The soil profile types are to be determined by the Consultant based on the geotechnical data reports. Structural Zone – Muscat

2A

Structural Zone – Salalah

1













The displacement to be used in deflection checks and for design of movement joints is the maximum inelastic response displacement, M, which is given by: M = 0.7R S Where R is the response modification factor given in UBC 1997 table 16N. 3.11.2 Directional effects Directional effects (also denoted orthogonal effects) shall be considered according to UBC 1997 sections 1630.1.1 and 1633.1 if the structure is irregular or a column forms part of two or more intersecting lateral-force resisting systems. The requirement that directional effects are considered may be satisfied by applying 100% of the prescribed design seismic forces in one direction plus 30% of the prescribed design seismic forces in the perpendicular direction. 3.11.3 P- Δ Effects P- Δ Effects shall be considered in accordance with UBC 1997 section 1630.1.3 and BS 5950-1 section 2.4.2.5. 3.11.4 Response spectrum analysis When the dynamic lateral force procedure is required for the earthquake loads a response













3.11.5 Seismic detailing requirements The seismic design according to the UBC 1997 gives a series of detailing requirements that shall be fulfilled. These requirements may in several cases overrule requirements given by the British Standards. 3.11.6 Seismic design of block work infill walls The UBC 1997 requires the effect of infill walls to be taken into account but does not state how this shall be done. The design of infill panels shall therefore be in accordance with the guidelines in BS EN 1998-1:2004. The reinforcement detailing of block work infill walls shall be in accordance with chapter 21 of the UBC 1997. 3.11.7 Interaction between sub- and superstructures of different stiffness The sudden drop of stiffness from the reinforced concrete part of substructures to steel superstructures may lead to relative motions out-of phase in between the sub- and superstructure. Such relative motions may be unacceptably large for steel columns in the superstructure. On the other hand, the same out-of-phase relative motions may provide the basis for a beneficial structural interaction in the sense that the overall seismic response of the substructure may be damped out. The Consultant/Contractor shall address these issues in a suitable manner subject to the













3.14 General robustness / disproportionate collapse The requirements of BS 8110 regarding minimum lateral forces and required ties between structural elements to ensure robustness shall be covered through the earthquake design and specific earthquake detailing requirements according to the UBC 1997. Robustness of concrete structures shall be provided based on BS 8110-1 section 2.2.2.2. If the robustness cannot comply with the requirements, the elements shall be designed as key elements according to BS 8110-2 section 2.6.2. Reinforcement detailing shall comply with section 1921.8 of UBC 1997, in addition to complying with British standard practice. Robustness of steel structures shall be provided based on BS 5950-1 section 2.4.5.3. If the robustness cannot comply with the requirements, the elements shall be designed as key elements according to BS 5950-1 section 2.4.5.4, applying the loads stated in section 12 of BS 6399-1.

3.15 Comfort requirements 3.15.1

General comfort requirements

The vibration serviceability requirements given in BS 5400-2:2006 appendix B shall be fulfilled for cantilevered and long span slabs or beams in bridges and/or bridge-like structures, e.g. fixed













*The deflection should in general be checked for the SLS load combinations in section 3.19.2. However the General Specification for Concrete Work requires that cambers corresponding to the deflection due to dead load are included. The dead load can therefore be disregarded in the SLS combinations in the deflection checks. ** The 20 mm requirement can be disregarded if the Consultant verifies that partitions etc. supported by or adjacent to the beam or slab are not damaged by the increased deflection or unacceptable cracks are developed.

For cantilevers the span equals twice the length of the cantilevered part. In addition to the above deflection requirements, deflections in structures shall comply with the deflection requirements for any roof lights, curtain walls etc connected to them. In case a part of the live load can be considered permanent this shall be taken in account in accordance with clause 3.3.3 of BS 8110-2. 3.16.2 Steel structures Maximum vertical deflection of beams due to imposed load (SLS*) Cantilevers carrying plaster or other brittle Span / 250 finish Other cantilevers Span / 100 Beams carrying plaster or other brittle finish Span / 500 Other beams Span / 200 Maximum horizontal deflection of columns due to imposed load and/or wind load (SLS) Tops of columns in single storey except portal Height / 500















3.16.4 Earthquake, building separations and movement joints The UBC 1997 requires all structures to be separated from adjoining structures. The minimum distance between two structures is given by:

Δ

MT =

√ ((Δ

Where Δ

M1 )

M1 and

+(Δ

2

Δ

M2 )

M2 is

2

)

the maximum inelastic response displacement for each structure.

Movement joints shall be able to cater for a total deformation Δ

MT

3.16.5 Special situations Special caution shall be taken in areas with conveyors and other equipment that may have additional deflection requirements due to functionality other than stated elsewhere in section 3.16.













The safety factors for the loads are given in the following subsections. In general the safety factors on dead load shall be set to 1.0 when the load has a beneficial effect on the structure. L, W or T shall be left out in cases where this causes more critical combinations. The load combinations given in the following sections shall be considered as the minimum requirements. The Consultant shall include additional load combinations (e.g. for the fire limit state FLS) in his design as appropriate. 3.18.1 Load combinations ULS Load combination 1a 1b 2a 3a

Steel structure

Concrete structure

1.4 D + 1.6 L + 1.21 EW ± 1.2 T 2 + 1.2 S2 1.0 D + 1.6 L + 1.21 EW ± T 2 + 1.2 S2 1.0 D + 1.6 L + 1.21 EW ± 1.2 T 2 + 1.2 S2 1.2 D + 1.2 L + 1.2 W + 1.21 EW ± T2 + 1.2 S2

1.4 D + 1.6 L + 1.21 EW 1.0 D + 1.6 L + 1.21 EW 1.4 D + 1.4 L + 1.21 EW 1.2 D + 1.2 L + 1.2 W + 1.21 EW













3.18.3 Load combinations ALS Load combination 7 8 9 10 11 12 13 14

Steel structures (1.2 + 0.5CaI) D + f 1 L ±1.0 f Eh (0.9 ± 0.5CaI) D ± 1.0 f Eh 1.2 D + f 1L ± 1.0 f Ώ0 Eh 0.9 D ± 1.0 f Ώ0 Eh Concrete Structure (1.32 + 0.55CaI) D + 1.1 f 1 L ± 1.1 f Eh (0.99 ± 0.55CaI) D ± 1.1 f Eh (1.32 + 0.55CaI) D + 1.1 f 1 L ± 2.2 f Eh (0.99 ± 0.55CaI) D ± 2.2 f Eh

According to UBC 1997 sections 1612.2.1 and 1612.4 the factor f1 shall be taken as 1.0 for floors in places of public assembly and for characteristic live loads in excess of 4.8 kN/m2. For













increased by a factor 1.1 as per exception 2. The increased load combinations are given as combination 11 and 12 of this design basis. According to UBC 1997 section 1921.8.3 shear reinforcement in beams and columns shall be designed using an earthquake effect twice that prescribed in UBC 1997 section 1626, i.e. load combination 13 and 14 shall be used for design of shear reinforcement. The use of the load combinations for all other structural systems, e.g. shear walls, shall be in accordance with UBC 1997 section 1921. 3.18.4 Load combinations, foundations The check of the soil bearing capacity shall be based on the following load combinations as the full safety factor shall be applied to the bearing capacity of the soil according to section 5 of this design basis. The design of RC pad footings and strip foundations (i.e. concrete and reinforcement etc.) shall be based on combination 1 through 12.













4.

Materials

4.1

Reinforced concrete

4.1.1

General

All concrete members shall be designed in accordance with BS 8110 unless otherwise stated sta ted or specifically agreed with the Engineer. BS 8007 shall apply as appropriate for concrete structures retaining aqueous liquids. 4.1.2

Partial safety factors

The partial safety factors (γm) for the strength of concrete for ULS in accordance with BS81101, table 2.2 are given below.















reinforcement in tension. However for practical reasons it shall be allowed to use a reduced modulus of elasticity instead provided the effective stiffness, i.e. Ec x Ic is the same. 4.1.4

Fire protection

All concrete structures shall be fire proofed by provision of adequate cover to reinforcement corresponding to the required fire rating in accordance with BS 8110-1 Section 3.3.6 and BS













Cast steel elements shall be designed in accordance with BS 5950-1 section 3.3, SCI publication 172 “Castings in Construction” and as specified in the General Specification for Structural Steelwork. 4.2.2

Partial safety factor

The partial safety factors (γm) for the strength of structural steel at ULS shall be in accordance













4.2.5

Bolted connections

The shear capacity of bolts shall be determined using the tensile stress area of the threaded part of the bolt. Connections between beams and columns in the main structural system shall be designed as friction grip connections if the connection is located within the dissipative zone.













4.3.1

Partial safety factors

Values of the partial safety factor for materials are given in the table below: Material Structural steel Reinforcement Concrete

SLS 1.0 1.0 1.0 or 1.3

ULS 1.10 1.15 1.5













Shear Wall ties Reinforced masonry Compression Flexure Shear Reinforcement

2.5 3.0

2.5 3.0 γm , γmv

2.3 2.3 2.0 1.15































































Design Basis r0

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