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1、BRITISH STANDARD CONFIRMED DECEMBER 1990 BS 4447:1973 Incorporating Amendment No. 1 Specification for The performance of prestressing anchorages for post-tensioned construction UDC 624.012.46:693.564:4:693.565.8:620.172.2 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:08:06 GMT+00:00 2006
2、, Uncontrolled Copy, (c) BSI BS 4447:1973 This British Standard, having been approved by the Cement, Lime and Gypsum Products Industry Standards Committee, was published under the authority of the Executive Board on 12 October, 1973 BSI 07-1999 First published March 1969 First revision October 1973
3、The following BSI references relate to the work on this standard: Committee reference CEB/22 Draft for comment 71/11660 ISBN 0 580 07865 5 Co-operating organizations The Cement, Lime and Gypsum Products Industry Standards Committee, under whose supervision this British Standard was prepared, consist
4、s of representatives from the following Government departments and scientific and industrial organizations. Association of Consulting Engineers British Precast Concrete Federation* British Quarrying and Slag Federation British Railways Board British Ready Mixed Concrete Association British Steel Cor
5、poration* Cement and Concrete Association* Cement Makers Federation Chemical Industries Association Concrete Society Ltd* Department of the Environment* Department of the Environment Building Research Establishment Federation of Civil Engineering Contractors* Greater London Council Gypsum Products D
6、evelopment Association Institution of Civil Engineers* Institution of Municipal Engineers Institution of Structural Engineers* Institution of Water Engineers National Federation of Building Trades Employers The Royal Institution of Chartered Surveyors Sand and Gravel Association Society of Chemical
7、Industry Welwyn Hall Research Association The Government department and scientific and industrial organizations marked with an asterisk in the above list, together with the following were directly represented on the committee entrusted with the preparation of this British Standard. Electricity Counc
8、il, The Central Electricity Generating Board and the Area Boards in England and Wales Amendments issued since publication Amd. No.Date of issueComments 6194November 1990 Indicated by a sideline in the margin Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:08:06 GMT+00:00 2006, Uncontrolled
9、 Copy, (c) BSI BS 4447:1973 BSI 07-1999i Contents Page Co-operating organizationsInside front cover Forewordii 1Scope1 2Definitions1 3General1 4Minimum performance1 5Test of load efficiency and of elongation of the anchored tendon2 6Test of dynamic behaviour of the anchored tendon3 7Test of force tr
10、ansfer to the end block3 8Test reports4 Appendix A Bursting reinforcement requirements for the test specimen5 Figure 1 Short term static tensile test2 Figure 2 Short term static compressive test4 Figure 3 Position of bursting reinforcement6 Publications referred toInside back cover Licensed Copy: sh
11、effieldun sheffieldun, na, Fri Dec 01 09:08:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4447:1973 ii BSI 07-1999 Foreword This British Standard was first published in March 1969. As a result of international experience it has been found that some revision to the methods covered were necessary a
12、nd the standard has therefore been revised. This standard describes three complementary methods of testing prestressing anchorages for post-tensioned concrete construction using wire, strand or bar tendons. These three methods of test are: 1) the test of static efficiency and of elongation of the an
13、chored tendon; 2) the test of dynamic behaviour of the anchored tendon; 3) the test of force transfer to the end block. The standard methods are intended to supply basic information on the performance of an anchorage under specified conditions, but it remains the responsibility of the structural eng
14、ineer to ensure that the anchorage system is detailed and used correctly in each application and according to the appropriate Codes of Practice. It is the responsibility of the manufacturer to maintain such quality controls as are necessary. It is not however practical for the anchorage manufacturer
15、 to carry out tests for all anchorage types and for all varieties of tendon material available in sufficient numbers to allow the characteristic efficiency and the characteristic elongation to be calculated for all the alternatives, since a minimum of twenty tests would be required in each case. How
16、ever, where the client nominates a tendon material for which the manufacturer has no test evidence, the manufacturer shall be entitled to request that he carry out up to three tests of the type described in Clause 4 using the nominated tendon before any performance figures are given. The apportionme
17、nt of the cost of these tests, including all labour, materials, transport and fees, shall be agreed between the client and the anchorage manufacturer. To comply with this standard, the anchorage when tested with a specific tendon must comply with the requirements of Clause 4. Anchorages which do not
18、 comply with the figure in Clause 4 may be used at proportionately reduced stressing forces by agreement between the manufacturer and the client. There are a number of practical considerations that can affect the efficiency of an anchorage which should be taken into account at the design stage of th
19、e structure. Some of these are: 1) the ease of ensuring full compaction of the concrete around the anchorage; 2) the degree of misalignment of the anchorage relative to the tendon axis; 3) the surface condition of the anchorage and tendon; 4) the possibility of extreme environmental conditions; 5) t
20、he correct reinforcement of the end block in accordance with good engineering practice. The design of end blocks is outside the scope of this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their corr
21、ect 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 6, an inside back cover and a back cover. This standard has been updated (see copyr
22、ight date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:08:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4447:1973 BSI 07-19991 1 Scope This British Standard specifies s
23、tandard test procedures to be used in establishing the satisfactory performance of prestressing anchorages of various types. Such fundamental data, being presented in certified form, may then be used in design with the knowledge that all the information has been derived from approved test procedures
24、. These methods are not intended to be adopted as routine acceptance tests. The Committee considers this approach to be practical, non-restrictive and well suited to the conditions existing in the industry without restricting future anchorage development. NOTEThe titles of the British Standards refe
25、rred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard the following definitions apply: 2.1 anchorage a mechanical device designed to retain the force in a stressed tendon 2.2 anchorage system a combination of the anchorages, the tendons
26、 and the reinforcement acting together within the end block to transmit the force in an ungrouted tendon to the prestressed concrete member 2.3 anchorage type anchorages of varying capacity but of the same design form 2.4 end block the end section of a prestressed concrete member which is specially
27、reinforced to resist the secondary stresses created by the anchorages 2.5 tendon an extensible steel element or group of elements used to impart prestress to a concrete member 3 General The maximum load on the anchorage generally occurs during the tensioning operation when a prestressing force is ap
28、plied. During and after lock-off, the prestressing force reduces for various reasons. This reduction can be caused by relaxation, concrete shrinkage and creep, anchorage pull-in and elastic shortening of the member where the prestressing force is applied successively through several separate stressi
29、ng operations. In the case of a fully bonded tendon, after the grout has hardened, any relaxation or creep within the anchorage zone will not affect the prestressing force beyond the end block since any change in force will be maintained by the bond between the tendon and the concrete. Similarly, an
30、y change in the force in fully bonded tendons due to an externally applied load will likewise be distributed by bond and will not increase the anchorage force. In the case of an unbonded tendon, any reduction in the anchorage force due to creep or relaxation will result in a lower prestressing force
31、 throughout the member. Any change in the force in the tendon due to an externally applied load could be transmitted directly to the anchorage. Therefore, in the case of unbonded tendons, it is essential to ensure that the anchorage and the end block are capable of retaining the final prestressing f
32、orce for an indefinite period and that they will withstand a specified cyclic loading depending on the type of application. 4 Minimum performance In order to comply with this standard, single anchorages when tested with a tendon of a quality not lower than the lowest characteristic strength specifie
33、d in BS 4486 or BS 5896 shall have the following minimum performances in at least three consecutive tests. 1) The actual efficiency of the anchored tendon shall not be lower than 92 %. The actual efficiency of the anchored tendon shall be taken as the ratio of the failure force as measured in Clause
34、 5 to the average ultimate tensile strength of the tendon. The average ultimate tensile strength shall be determined from three specimens taken at random from the total length of the tendon used in the tests and tested in accordance with the methods specified in BS 18 or BS 4545 as appropriate. Lice
35、nsed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:08:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4447:1973 2 BSI 07-1999 2) The percentage elongation at maximum load as measured in Clause 5 shall not be less than 1.8 %. 3) For an unbonded tendon, when tested in accordance with the method gi
36、ven in Clause 6, not more than 5 % of the initial cross sectional area of the tendon shall fail. 4) The anchorage system tested in accordance with the test given in Clause 7 shall be capable of supporting a load of 1.1 fpu (where fpu is the characteristic strength of the tendon for which the anchora
37、ge is designed). In the case of a range of anchorages of various capacities but of similar design form using the same size and type of tendon material, the intermediate sizes shall be deemed to comply with the requirements of the whole standard provided at least three consecutive test results in eac
38、h of two sizes comply. 5 Test of load efficiency and of elongation of the anchored tendon 5.1 Description of test. This is a short term static tensile test carried out on an anchorage attached to a tendon (see Figure 1). Figure 1 Short term static tensile test Licensed Copy: sheffieldun sheffieldun,
39、 na, Fri Dec 01 09:08:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4447:1973 BSI 07-19993 5.2 Test specimen. The test specimen shall consist of suitable lengths of wire, strand or bar held at each end by the anchorage under test, or at one end by the anchorage and at the other by a special devic
40、e which ensures that the failure occurs at a point remote from that end. The test shall be carried out using, at least at one end, all parts of the anchorage which contribute to the actual gripping or supporting of the tendon but not necessarily those parts normally cast into the concrete. The metho
41、d of supporting the anchorage parts shall be chosen by the anchorage manufacturer but shall simulate the effect of any geometric deviation of any individual wires, strand or bars within the anchorage. The number of wires, strands or bars forming the tendon shall be the maximum for which the anchorag
42、e is designed. 5.3 Test procedure. The test load shall be applied uniformly on tendons which have been previously prestressed by a representative prestressing operation to not less than 0.70 of the characteristic strength of the tendon, either by calibrated jacks or by a suitable tensile testing mac
43、hine. Alternatively, where it can be demonstrated that the prestressing operation has no effect on the load transfer, the whole of the test load may be applied by calibrated jacks or by a suitable testing machine. The failure force shall be the force at which the test specimen no longer supports any
44、 increase in the loading at which point the total elongation of the tendon shall be recorded, or deduced from elongation readings at lower loadings. The test load shall be applied at a rate of not more than 200 N/mm2 per minute and the tests shall be carried out at ambient temperature unless otherwi
45、se stated. The percentage elongation shall be taken as the ratio of the net elongation to the original length of the tendon: the anchored length shall not be less than 3 m. Due allowance for draw in, slip and other extraneous causes shall be taken into account in determining the net elongation, whic
46、h shall be measured over the outside face of the anchorages or special device. The characteristic strength of an anchored tendon is the product of the characteristic strength of the tendon times the actual efficiency. 6 Test of dynamic behaviour of the anchored tendon 6.1 Description of test. The te
47、st is a fluctuating load test carried out in a tensile testing machine or a fatigue testing machine applying a fluctuating tensile force. It is applicable to unbonded tendons only. 6.2 Test specimen. The test specimen shall be similar to that for the test given in Clause 5, but with the tendon lengt
48、h appropriate to the testing machine used. In the case of a very large tendon for which the test loads exceed the capacity of equipment available, the number of elements in the tendon may be reduced provided that they are distributed uniformly in the anchorage and their geometric arrangement is not
49、more favourable than in the complete tendon. In preparing the test specimen, such measures as would be taken in practice to avoid fretting of any part of the tendon shall be taken. 6.3 Test procedure. The test specimen shall be subjected to a fluctuating force between 0.60 fpuand 0.65 fpu at a frequency not exceeding 10 Hz for a minimum of 2 106 cycles. Loss of not more than 5 % of the initial cross-sectional area of the tendon due to fatigue failures of individual elements shall not invalidate the test. 7 Test of force transfer to the end block 7.1 Description of test
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