Singapore Standards CP 65 1 : 1999 (Code of practice for structural use of co

91.080.40 Concrete structures

Gives recommendations for the structural use of concrete in buildings and structures, excluding bridges, water-retaining structures and structural concrete made with high alumina cement.

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Contents

Foreword

Section One - General

1.1 Scope

1.2 Definitions

1.3 Symbols

Section Two - Design objectives and general recommendations

2.1 Basis of design

2.2 Structural design

2.3 Inspection of construction

2.4 Loads and material properties

2.5 Analysis

2.6 Designs based on tests

Section Three - Design and detailing : Reinforced concrete

3.1 Design basis and strength of materials

3.2 Structures and structural frames

3.3 Concrete cover to reinforcement

3.4 Beams

3.5 Solid slabs supported by beams or walls

3.6 Ribbed slabs (with solid or hollow blocks or voids)

3.7 Flat slabs

3.8 Columns

3.9 Walls

3.10 Staircases

3.11 Bases

3.12 Considerations affecting design details

Section Four - Design and detailing : Prestressed concrete

4.1 Design basis

4.2 Structures and structural frames

4.3 Beams

4.4 Slabs

4.5 Columns

4.6 Tension members

4.7 Prestressing

4.8 Loss of prestress, other than friction losses

4.9 Loss of prestress due to friction

4.10 Transmission lengths in pre-tensioned members

4.11 End blocks in post-tensioned members

4.12 Considerations affecting design details

Section Five - Design and detailing : Precast and composite construction

5.1 Design basis and stability provisions

5.2 Precast concrete construction

5.3 Structural connections between precast units

5.4 Composite concrete construction

Section Six – Concrete : Materials, specification and construction

6.1 Materials and specification

6.2 Concrete construction

Section Seven - Specification and workmanship : Reinforcement

7.1 General

7.2 Cutting and bending

7.3 Fixing

7.4 Surface condition

7.5 Laps and joints

7.6 Welding

Section Eight - Specification and workmanship : Prestressing tendons

8.1 General

8.2 Handling and storage

8.3 Surface condition

8.4 Straightness

8.5 Cutting

8.6 Positioning of tendons and sheaths

8.7 Tensioning the tendons

8.8 Protection and bond of prestressing tendons

8.9 Grouting of prestressing tendons

ANNEX

A Grouting of prestressing tendons

TABLES

2.1 Load combinations and values of γf for the ultimate limit state

2.2 Values of γm for the ultimate limit state 19

3.1 Strength of reinforcement

3.2 Exposure conditions

3.3 Adjustments to minimum cement contents for aggregates other than 20 mm

nominal maximum size

3.4 Nominal cover to all reinforcement (including links) to meet durability requirements

3.5 Nominal cover to all reinforcement (including links) to meet

specified periods of fire resistance

3.6 Design ultimate bending moments and shear forces

3.7 Values of the factor β f

3.8 Form and area of shear reinforcement in beams

3.9 Values of vc, design concrete shear stress

3.10 Basic span/effective depth ratios for rectangular or flanged beams

3.11 Modification factor for tension reinforcement

3.12 Modification factor for compression reinforcement

3.13 Ultimate bending moment and shear forces in one-way spanning slabs

3.14 Bending moment coefficients for slabs spanning in two directions

at right-angles, simply-supported on four sides

3.15 Bending moment coefficients for rectangular panels supported on four sides

with provision for torsion at corners

3.16 Shear force coefficients for uniformly loaded rectangular panels supported on

four sides with provision for torsion at corners

3.17 Form and area of shear reinforcement in solid slabs

3.18 Minimum thickness of structural toppings

3.19 Ultimate bending moment and shear forces for flat slabs of three or

more equal spans

3.20 Distribution of design moments in panels of flat slabs

3.21 Values of β for braced columns

3.22 Values of β for unbraced columns

3.23 Values of βa

3.24 Values of the coefficient β

3.25 Maximum slenderness ratio for reinforced walls

3.26 Bar schedule dimensions : Deduction for permissible deviations

3.27 Minimum percentages of reinforcement

3.28 Values of bond coefficient β

3.29 Ultimate anchorage bond lengths and lap lengths as multiples of bar size

3.30 Clear distance between bars according to percentage redistribution

4.1 Design flexural tensile stresses for class 2 members: Serviceability limit

state: Cracking

4.2 Design hypothetical flexural tensile stresses for class 3 members

4.3 Depth factors for design tensile stresses for class 3 members

4.4 Conditions at the ultimate limit state for rectangular beams with pre-tensioned tendons or post-tensioned tendons having effective bond

4.5 Values of Vco/bvh

4.6 Relaxation factors

4.7 Design bursting tensile forces in end blocks

4.8 Nominal cover to all steel (including links) to meet durability requirements

4.9 Nominal cover to all steel to meet specified periods

4.10 Minimum cover to curved ducts

4.11 Minimum distance between centre-lines of ducts in plane of curvature

5.1 Allowances for effects of spalling at supports

5.2 Allowances for effects of spalling at supported members

5.3 Values of tan αf for concrete connections

5.4 Design flexural tensile stresses in in situ concrete

5.5 Design ultimate horizontal shear stress at interface

6.1 Minimum periods of curing and protection

6.2 Minimum period before striking formwork (concrete made with ordinary

or sulphate-resisting Portland cement)

FIGURES

2.1 Short term design stress-strain curve for normal-weight concrete

2.2 Short term design stress-strain curve for reinforcement

2.3 Short term design stress-strain curve for prestressing tendons

3.1 Flow chart of design procedure

3.2 Minimum dimensions of reinforced concrete members for fire resistance

3.3 Simplified stress block for concrete at ultimate limit state

3.4 System of bent-up bars

3.5 Shear failure near supports

3.6 Effective width of a solid slab carrying a concentrated load near

an unsupported edge

3.7 Definition of panels and bays

3.8 Explanation of the derivation of the coefficients of Table 3.15

3.9 Division of slab into middle and edge strips

3.10 Distribution of load on a beam supporting a two-way spanning slab

3.11 Types of column head

3.12 Division of panels in flat slabs

3.13 Definition of breadth of effective moment transfer strip, be, for various typical cases

3.14 Shear at slab-column connection

3.15 Application of 3.7.6.2 and 3.7.6.3

3.16 Definition of a shear perimeter for typical cases

3.17 Zones for punching shear reinforcement

3.18 Shear perimeter of slab with openings

3.19 Shear perimeters with loads close to free edge

3.20 Braced slender columns

3.21 Unbraced slender columns

3.22 Biaxially bent column

3.23 Critical section for shear check in a pile cap

3.24 Simplified detailing rules for beams

3.25 Simplified detailing rules for slabs

5.1 Continuity of ties: Bars in precast member lapped with bar in in situ concrete

5.2 Continuity of ties: Anchorage by enclosing links

5.3 Continuity of ties: Bars lapped within in situ concrete

5.4 Schematic arrangement of allowance for bearing

Index

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Foreword

This Part of CP 65 has been prepared by the Technical Committee on Structural Use of Concrete under the direction of the Construction Industry Practice Committee. It is a revision of CP 65 : Part 1 : 1996 - 'Code of practice for structural use of concrete - Part 1 : Design and construction.'

CP 65 is published in two parts. They are:

Part 1. Design and construction

Part 2. Special circumstances

CP 65 : Part 1 encompasses the structural use of reinforced and prestressed concrete both cast-in-situ and precast and gives recommendations for design and construction of buildings. It is based on the British Standard BS 8110 : Part 1 : 1997.

The first edition of CP 65 : Parts 1 and 2 : 1996, which was based on BS 8110 : Part 1 : 1985, was approved by the Standards Council in November 1996. Its publication in 1997 was withheld due to major revisions to the base standard in 1997. CP 65 : Part 2 : 1996 was also withheld since CP 65 :

Part 1 : 1996 was being revised. To resolve the issue concerning the reduction of the partial safety factor of steel reinforcement from 1.15 to 1.05, numerous surveys were conducted to determine the quality of steel reinforcement used in Singapore. The conclusion reached was that more data had to be collected for a period of two years to determine more accurately the quality of steel reinforcement used in Singapore. Therefore, the partial safety factor of steel reinforcement remains at 1.15.

Most of the recommendations in CP 65 are as given in BS 8110 : Part 1 : 1997. Changes that are recommended by the British Standard have been incorporated into Part 1. One major exception is that the partial safety factor of steel reinforcement remains at 1.15. Another is that the section on