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1、BRITISH STANDARD BS 7973-1:2001 Spacers and chairs for steel reinforcement and their specification Part 1: Product performance requirements ICS 77.140.99 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Licensed Copy: London South Bank University, London South Bank University,
2、Fri Dec 08 14:29:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7973-1:2001 This British Standard, having been prepared under the direction of the Sector Policy and Strategy Committee for Building and Civil Engineering, was published under the authority of the Standards Policy and Strategy Committ
3、ee on 16 October 2001 16 October 2001 The following BSI references relate to the work on this standard: Committee reference B/525/2 Draft for comment 00/104696 DC ISBN 0 580 38556 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical C
4、ommittee B/525, Building and civil engineering structures, to Subcommittee B/525/2, Structural use of concrete, upon which the following bodies were represented: Association of Consulting Engineers British Cement Association British Precast Concrete Federation Ltd. Building Research Establishment Co
5、ncrete Society Ltd. Department of the Environment, Transport and the Regions (Construction Directorate) Department of the Environment, Transport and the Regions (Highways Agency) Institution of Civil Engineers Institution of Structural Engineers UK Steel Association Amendments issued since publicati
6、on Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:29:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7973-1:2001 BSI 16 October 2001 i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Normative references1 3Ter
7、ms and definitions1 4Designations and symbols2 5Spacers and chair categories and applications3 6General requirements for spacers and chairs3 7Dimensions3 8Stability4 9Load bearing capacity6 10Fixity6 11Marking7 12Inspection and testing8 Annex A (normative) Load testing9 Bibliography12 Figure 1 Geome
8、trical requirements of clip-on spacers and wheel spacers5 Figure 2 Isometric view of the fixity test for clip-on spacers6 Figure A.1 Apparatus for load testing spacers10 Figure A.2 Position of a wheel spacer for load testing10 Figure A.3 Apparatus for point load testing chairs11 Table 1 Applications
9、 for spacers and chairs in terms of category3 Table 2 Point test load for spacers and chairs7 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:29:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7973-1:2001 ii BSI 16 October 2001 Foreword This British Standard
10、 has been prepared by Technical Committee B/525/2. It is the first edition of the standard. Until now the inadequate manufacture and use of spacers and chairs and method of tying has been a major cause of misplaced steel reinforcement resulting in decreased durability of reinforced concrete. In Nove
11、mber 1989 the Concrete Society published Spacers for reinforced concrete (CS101) 1 providing recommendations for achieving cover but until now no British Standard has existed. All British Standards for reinforced concrete design and construction (e.g. BS 8110-1, BS 5400-7 and BS 8007) state that the
12、 nominal cover specified applies to all reinforcement including links. This British Standard gives standardized performance requirements for and methods of testing spacers and chairs. It is based on Concrete Society Report CS 101 “Spacers” 1 published in November 1989 and was developed to be consist
13、ent with the Comit Euro-International du Bton Bulletin dInformation No. 201 Spacers, chairs and tying of steel reinforcement 2. Performance and testing requirements are based on tests carried out on the capacity of spacers and chairs which have been available in the UK for many years and which have
14、proved to be satisfactory in use. It is imperative that chairs and spacers conforming to BS 7973-1 are applied in accordance with BS 7973-2. Abnormal loads, such as those exerted by construction plant, storage of materials and heavy reinforcement cages, can overload spacers and chairs. Under abnorma
15、l load conditions adequate support is most suitably achieved using heavy (H) category line spacers at centres which depend on the exact size and nature of the load. Annex A is normative. A British Standard does not purport to include all necessary provisions of a contract. Users of British Standards
16、 are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 12, an inside back cover and a back cover. The BSI c
17、opyright notice displayed in this document indicates when the document was last issued. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:29:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7973-1:2001 BSI 16 October 2001 1 1 Scope This part of this British Sta
18、ndard specifies product performance requirements for spacers and chairs sufficient to achieve and maintain cover to reinforcement in in situ reinforced concrete members subject to normal construction loads when used in accordance with BS 7973-2. NOTE Where appropriate, the basic principles can be ap
19、plied to precast concrete or proprietary systems. Product requirements for spacers and chairs include their dimensions, identification, point load strength, permanent deflection after loading, stability and fixity. 2 Normative references The following normative documents contain provisions which, th
20、rough reference in this text, constitute provisions of this part of this British Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. For undated references, the latest edition of the publication referred to applies. BS 1881-108, Testing
21、concrete Part 108: Method for making test cubes from fresh concrete. BS 1881-111, Testing concrete Part 111: Method of normal curing of test specimens (20?C method). BS 1881-116, Testing concrete Part 116: Method for determination of compressive strength of concrete cubes. BS 4482, Specification for
22、 cold reduced steel wire for reinforcement of concrete. BS 4483, Steel fabric for the reinforcement of concrete. BS 7973-2, Spacers and chairs for steel reinforcement and their specification Part 2: Fixing and application of spacers and chairs and tying of reinforcement. BS 8110-1:1997, Structural u
23、se of concrete Part 1: Code of practice for design and construction. 3 Terms and definitions For the purposes of this British Standard the following terms and definitions apply. 3.1 cover distance between the steel reinforcement and the nearest face of the concrete NOTE 1 Cover, or nominal cover, is
24、 the cover specified by the structural designer on the structural design drawings. NOTE 2 As the term “minimum cover” can be confused with “nominal cover”, it should not be used. 3.2 spacer component which is placed to maintain cover between the reinforcement and formwork or blinding and which provi
25、des cover or support for reinforcement at a single point on one or more faces of the formwork or blinding NOTE As stated in BS 8110-1:1997, Table 3.4, 15 mm cover spacers may only be used where the nominal maximum size of aggregate does not exceed 15 mm. 3.3 end spacer spacer designed to fit on the
26、ends of reinforcement to provide end cover 3.4 line spacer spacer normally made of either plastics or cementitious bars, normally of constant cross-section, used to support horizontal layers of reinforcement or horizontal continuous steel chairs 3.5 rib spacer spacer used where there are no links wi
27、thin the ribs and which are designed to support one or more main bars in hollow pot, waffle, trough and ribbed slabs and to provide spacing between the sides of the hollow pot, waffle, trough and rib forms Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:29:09
28、 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7973-1:2001 2 BSI 16 October 2001 3.6 wheel spacer spacer having a circular section, perpendicular to the bar to which it is attached, used for maintaining cover in vertical members to the reinforcement nearest the surface of the concrete 3.7 clip-on sp
29、acer spacer in which the clip action is an integral part of the design of the spacer NOTE A clip-on spacer is usually made of plastics. 3.8 wire-on spacer spacer that is attached to the bar by the use of tying wire NOTE Wire-on spacers are usually cementitious. 3.9 chair component in sizes of 50 mm
30、to 300 mm normally manufactured from steel wire conforming to BS 4482 commonly used to support top horizontal reinforcement or to separate vertical reinforcement in walls NOTE Chairs may be individual, continuous, or circular. Chair heights above 300 mm are normally scheduled using bent bar reinforc
31、ement. 3.10 individual chair chair manufactured in standard heights of between 75 mm and 300 mm inclusive and used to support reinforcement at one point 3.11 continuous chair chair manufactured to provide a straight line of support at a uniform height normally in the range of 45300 mm NOTE Continuou
32、s chairs are generally available in continuous lengths of up to 2 000 mm. 3.12 circular chair steel chair delivered flat and formed into circles on site 3.13 welded fabric cross-over arrangement of longitudinal wires and cross wires that are welded together at the cross-over points in a shear resist
33、ant manner, conforming to BS 4483 4 Designations and symbols The following designations and symbols are used throughout this British Standard. cCover or nominal cover. dThe nominal size of the bar nearest the surface of the concrete including links, used to determine the frequency of spacers along t
34、he bar to which they are fixed. For the spacing of chairs, d is the nominal size of the bar or wire that the chair is supporting. DThe nominal size of the main bar. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:29:09 GMT+00:00 2006, Uncontrolled Copy, (c) B
35、SI BS 7973-1:2001 BSI 16 October 2001 3 5 Spacers and chair categories and applications Spacer and chair categories required for particular applications shall be in accordance with Table 1. Criteria for assessing the spacer category shall be in accordance with Table 2. Table 1 Applications for space
36、rs and chairs in terms of category 6 General requirements for spacers and chairs 6.1 Materials of manufacture Spacers and chairs shall be manufactured from three basic materials: plastics, cementitious material or steel wire. The material of manufacture shall have an equivalent durability when it is
37、 in place to that of the concrete itself. NOTE It is important that the spacer or chair does not cause any deterioration to the reinforcement or the concrete, including not allowing free passage of water to the reinforcement nor causing spalling of the finished face. 6.2 Requirements for non-cementi
38、tious spacers Non-cementitious spacers shall satisfy the condition that any cross-section perpendicular to the bar has at least 25 % voids within the enclosed perimeter. 6.3 Requirements for cementitious spacers The mix used for cementitious spacers shall have a cube strength of at least 50 N/mm2 at
39、 28 days when cast, cured and tested in accordance with BS 1881-108, BS 1881-111, and BS 1881-116 respectively. In accordance with BS 8110-1 concrete spacers shall not be made on the construction site. 6.4 Requirements for steel chairs When steel chairs are required to support reinforcement off an e
40、xposed face, the ends of each chair leg shall be encased in a protective tip, such as a closed plastics sleeve, for a distance of at least 40 mm. Continuous and circular chairs shall comprise top and bottom wires of equal size and quality to which shall be welded transverse or lattice wires to space
41、 them. NOTE 1 If the chair is higher than 150 mm, strengthening may be required to meet the performance requirements of this British Standard. NOTE 2 The performance requirements of this British Standard are based on the use of 2 m lengths formed into circles of 570 mm diameter used to support the w
42、elded fabrics specified. 7 Dimensions 7.1 Preferred spacer and chair dimensions The standard range of spacers shall be for nominal covers from 15 mm to 75 mm in 5 mm increments. The standard range of chairs shall be for heights of 75 mm to 200 mm. NOTE As stated in BS 8110-1:1997, Table 3.4, 15 mm c
43、over spacers may only be used where the nominal maximum size of aggregate does not exceed 15 mm. Spacer and chair categoryApplication Light (L)To provide cover in vertical members to the reinforcement nearest the surface of the concrete or to horizontal reinforcement in small sections not subject to
44、 any foot traffic. Not suitable for reinforcement greater than 16 mm in size. Normal (N)To provide cover to reinforcement where the size of reinforcement is 20 mm or less. Heavy (H)To provide cover to reinforcement where the size of reinforcement is greater than 20 mm. Chairs (C)To support the top r
45、einforcement in slabs, so as to provide the required top cover or to separate layers of reinforcement. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:29:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7973-1:2001 4 BSI 16 October 2001 7.2 Dimensional tolera
46、nces for spacers The tolerance on the spacer dimension providing the cover shall be 1 mm for covers/heights up to 75 mm and 2 mm for larger cover/heights over 75 mm. 7.3 Dimensional tolerances for chairs The tolerance on the chair dimensions providing the cover or the specified height shall be 2 mm.
47、 For continuous and circular chairs where the nominal cover dimension is provided by a longitudinal element any side-supporting element shall not protrude beyond the longitudinal element by more than 3 mm. 7.4 Identification of the cover dimensions The nominal cover dimension of the spacer shall alw
48、ays be displayed on its packaging. Wherever possible, as part of the manufacturing process, the nominal cover dimension shall be indicated on the actual spacer. NOTE Single cover spacers are recommended. The maximum number of covers on each spacer shall be two with the value and orientation clearly
49、marked on the actual spacer. 7.5 Wire-on spacers The dimension of a wire-on spacer at its base shall be at least 20 mm measured in the direction of the bar which it is supporting and at least 0.75 of the cover dimension perpendicular to the bar. 7.6 Clip-on spacers As clip-on spacers have varying dimensional requirements relating to their fixity, they shall conform to clause 8. 7.7 Chairs 7.7.1 The distance between any two legs of an individual chair shall be not less than 0.5 of the specified height of the chair. 7.