BS 5977-1-1981 Lintels - Method for assessment of load《门窗过梁 第1部分 载荷评定方法》.pdf

1、BRITISH STANDARD BS 5977-1:1981 Incorporating Amendment No. 1 Lintels Part 1: Method for assessment of load UDC 624.072.22.042:692.299BS5977-1:1981 This British Standard, having been prepared under the directionof the Elements and Components (of Diverse Materials) for Building Standards Committee, w

2、as published underthe authority of the Executive Board and comes intoeffect on 31 December 1981 BSI 01-1999 The following BSI references relate to the work on this standard: Committee reference ECB/36 Draft for comment 79/13060 DC ISBN 0 580 12486 X Cooperating organizations The Elements and Compone

3、nts (of Diverse Materials) for Buildings Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: The organizations marked with an asterisk in the above list, together with the following, were directly represented on the Technical

4、 Committee entrusted with the preparation of this British Standard: Agrment Board* Health and Safety Executive Aluminium Federation Incorporated Association of Architects and Asbestos Cement Manufacturers Surveyors Association Limited Institute of Building Control Brick Development Association* Inst

5、itute of Quality Assurance British Ceramic Research Association Institution of Municipal Engineers British Hardware Federation Institution of Structural Engineers* British Plastics Federation Mastic Asphalt Council and Employers British Precast Concrete Federation Ltd.* Federation British Steel Indu

6、stry* National Council of Building Materials British Woodworking Federation Producers Consumer Standards Advisory Committee National Federation of Building Trades of BSI Employers Convention of Scottish Local Authorities National Federation of Roofing Contractors Department of the Environment (Build

7、ing Royal Institute of British Architects* Research Establishment, Princes Royal Institution of Chartered Surveyors* Risborough Laboratory) Scottish Development Department Department of the Environment (Housing Society of Chemical Industry and Construction) Timber Research and Development Department

8、 of the Environment (PSA)* Association Flat Glass Manufacturers Association Trades Union Congress Glass and Glazing Federation Aerated Autoclaved Concrete Products Greater London Council Association Institution of Building Control Officers Ltd. Aggregate Concrete Block Association North Wales Slate

9、Quarries Association British Precast Concrete Federation Ltd. Steel Lintel Manufacturers Association Department of the Environment (Building Zinc Development Association Research Establishment) Individual expert District Surveyors Association Amendments issued since publication Amd. No. Date of issu

10、e Comments 4796 April 1985 Indicated by a sideline in the marginBS5977-1:1981 BSI 01-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Definitions 1 4 Basic principles 1 5 Limiting conditions 2 6 Loads 3 7 Assessment of load for lintel supportin

11、g wall without openings within the interaction zone 3 8 Assessment of load for lintel supporting wall with one or more openings within the interaction zone 3 9 Assessment of load for lintel directly supporting roof or point loads 3 Appendix A Use of assessed loads for design or selection of lintels

12、5 Figure 1 Load triangle and interaction zone 1 Figure 2 Dispersion of loads 2 Figure 3 Effect of openings above the lintel 4 Figure 4 Example showing the loads on lintel with floor, partition and opening over the lintel 5 Figure 5 Example showing the loads on lintels supporting walls 6 Table 1 Conv

13、ersion factors for determining equivalent UDLs from assessed UDLs 7 Table 2 Conversion factors for determining equivalent UDLs from point loads close to the lintel 7 Publications referred to Inside back coverBS5977-1:1981 ii BSI 01-1999 Foreword This British Standard has been prepared under the dire

14、ction of the Elements and Components (of Diverse Materials) for Building Standards Committee and covers the design and use of all types of lintel (up to4.5m in span) in masonry. This Part describes a method for assessing the load carried by lintels. Part 2: of this standard is a specification for pr

15、efabricated lintels. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages Thi

16、s document comprises a front cover, an inside front cover, pages i and ii, pages1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS5977-1

17、:1981 BSI 01-1999 1 1 Scope This Part of BS5977 describes a method for assessing the load carried by lintels in masonry: a) where lintels span up to4.5m in single storey buildings and up to3.6m in two or three storey buildings in normal domestic use; and b) where no openings are wholly or partly wit

18、hin the load triangle (see3.2). Appendix A gives guidance on the use of assessed loads for design or selection of lintels, but does not cover assessment of the overall stability of the structure or the design of adjacent masonry. NOTEIt has been assumed in the drafting of this Part that the assessme

19、nt of load on a lintel is entrusted to chartered structural or civil engineers or other appropriately qualified persons, for whose guidance it has been prepared. The responsibility for providing adequate support for lintels and for compatibility between lintels and other parts of the supporting stru

20、cture rests with the designer responsible for the overall stability of the building. For guidance, see BS 5628-1. 2 References The titles of the standards publications referred to in this standard are listed on the inside back cover. 3 Definitions For the purposes of this British Standard, the follo

21、wing definitions apply. 3.1 lintel a beam spanning an opening in a wall 3.2 load triangle a45 triangle having1.1times the clear span of the lintel as its base (seeFigure 1) 3.3 interaction zone a zone outside the load triangle but within a60 triangle having1.1times the clear span of the lintel as it

22、s base (seeFigure 1) 3.4 application level the top surface of the lintel under consideration (seeFigure 1) 3.5 application length the length over which a load is distributed at the application level (seeFigure 2 andFigure 3) 3.6 equivalent uniformly distributed load (UDL) that uniformly distributed

23、load which gives the same bending moment at the centre of the span as the maximum bending moment anywhere in the span given by the actual loads 4 Basic principles 4.1 General. Experience has shown that, subject to the conditions given in4.2, it is safe to design a lintel to carry less than the sum o

24、f the applied loads and the weight of masonry immediately above the lintel. The remainder is dispersed through the masonry on either side of the lintel. Figure 1 Load triangle and interaction zoneBS5977-1:1981 2 BSI 01-1999 4.2 Assumptions. For the methods described in clauses7 and8, it is assumed t

25、hat: a) all the weight of the masonry within the load triangle is carried as a load on the lintel; b) any point or distributed loads applied to the masonry within the load triangle are dispersed at45 and carried by the lintel seeFigure 2(a); c) any point or distributed loads applied to the masonry w

26、ithin the interaction zone are reduced by50%, dispersed at45 and carried by the lintel seeFigure 2(b); d) the weight of masonry in the interaction zone is not carried by the lintel. 5 Limiting conditions For the methods described in clauses7 and8, it is assumed that the following limiting conditions

27、 are satisfied. a) The masonry is constructed following the recommendations of BS5628-3. b) The height of masonry above the lintel at mid-span is not less than0.6times the clear span of the lintel. c) The height of masonry above the supports is not less than600mm. d) The masonry is continuous within

28、 the area defined by the conditions given inb) andc). e) Where there is a single opening spanned by the lintel, the width of masonry on either side of the opening is not less than600mm or 0.2times the clear span of the lintel, whichever is the greater. Figure 2 Dispersion of loadsBS5977-1:1981 BSI 0

29、1-1999 3 f) Where there are a series of openings at the level of the opening spanned by the lintel, the length of masonry between the external corner of the wall and the side of the adjacent opening is not less than600mm or0.2times the longest clear span, whichever is the greater. Where conditionsb)

30、, c)andd) are not satisfied, seeclause9. 6 Loads The principal dead and imposed loads on a lintel arise from one or more of the following: a) masonry; b) floors; c) roofs; d) partitions; e) trimmer beams; f) self-weight of the lintel. NOTEFor guidance, see BS 648 and BS6399-1. 7 Assessment of load f

31、or lintel supporting wall without openings within the interaction zone Where the wall supported by the lintel has no other openings within the interaction zone seeFigure 3(a), the load carried by the lintel shall be assessed as follows. a) Take the load due to the masonry above the lintel to be the

32、weight of masonry within the load triangle. b) Disperse any loads applied to the masonry within the load triangle at45 and consider them uniformly distributed at the application level seeFigure 2(a). c) Reduce all loads applied to the masonry within the interaction zone by50% and then disperse them

33、at45 to produce a uniformly distributed load at the application level seeFigure 2(b). d) Neglect the weight of masonry in the interaction zone. e) Neglect loads applied outside the interaction zone. f) Add the above components of the applied loads to the self-weight of the lintel to obtain the total

34、 design load. 8 Assessment of load for lintel supporting wall with one or more openings within the interaction zone 8.1 Openings that do not intersect boundaries of the interaction zone shall be neglected seeFigure 3(a). 8.2 Where openings intersect the boundaries of the interaction zone, the effect

35、 is to apply an additional load to the lintel unless a single opening crosses the entire interaction zone seeFigure 3(b) and Figure 3(c). The intensity of load across the sectionxy shown inFigure 3(c) shall be assessed by taking into account all self-weight and applied loads on the wall above this l

36、evel. The load across the sectionxy, which lies in the interaction zone, shall be halved before dispersing it at45 to the lintel below. If two openings intersect the interaction zone, the load shall be taken to act at the bottom of the lowest opening. All other loads shall be assessed as described i

37、n clause7. NOTEExamples showing loads on lintels supporting walls with openings are given inFigure 4 andFigure 5. 9 Assessment of load for lintel directly supporting roof or point loads Where the lintel directly supports a roof or a point load and in other cases where the conditionsb), c)ord) given

38、in clause5 are not satisfied, the load on the lintel shall be taken to be the full value of the imposed load, plus the self-weight of the lintel.BS5977-1:1981 4 BSI 01-1999 Figure 3 Effect of openings above the lintelBS5977-1:1981 BSI 01-1999 5 Appendix A Use of assessed loads for design or selectio

39、n of lintels A.1 Design. The maximum bending moment, shear and deflection of a lintel are derived from the assessed loads and the lintel designed using normal structural engineering principles. A.2 Selection of lintels using published load-span tables. For selection of lintels using published load-s

40、pan tables, it may be convenient to convert triangular loads and part span loads to the equivalent uniformly distributed loads (see3.6) over the whole span. However, it should be noted that: a) equivalent uniformly distributed loads do not give correct shear forces; and b) bending moments calculated

41、 at mid-span by the use of equivalent uniformly distributed loads may occur in practice at other points in the span. Thus if lintels do not have a uniform bending strength throughout their length, it is essential to use equivalent uniformly distributed loads with discretion. Equivalent uniformly dis

42、tributed loads for assessment of bending strength and deflection are calculated as follows: a) for triangular loads W e= 1.33 W b) for uniformly distributed loads over part of the length of the lintel, or for point loads W e= K W where W is the assessed load (see clauses7, 8 and9), W e is the equiva

43、lent UDL, K is the appropriate factor taken from Table 1orTable 2. Figure 4 Example showing the loads on lintel with floor, partition and openingoverthelintelBS5977-1:1981 6 BSI 01-1999 NOTEAll wall, floor and roof loads in the area bounded by vertical linesA andB are applied across the sectionXX to

44、 the lintel under consideration. Figure 5 Example showing the loads on lintels supporting wallsBS5977-1:1981 BSI 01-1999 7 Table 1 Conversion factors for determining equivalent UDLs from assessed UDLs a Table 2 Conversion factors for determining equivalent UDLs from point loadsclosetothelintel a n K

45、 n K 0 0.05 0.1 0.15 0.2 0.25 0.3 0.333 0.35 0.4 0.45 0.5 0.55 0.60 0.65 0.666 0.70 0.75 0.80 0.85 0.90 0.95 1.00 0.190 0.361 0.513 0.648 0.766 0.867 0.926 0.953 1.024 1.081 1.125 1.156 1.176 1.185 1.185 1.183 1.172 1.152 1.124 1.089 1.047 1.00 0 0.05 0.1 0.15 0.2 0.25 0.3 0.333 0.35 0.4 0.45 0.5 0.

46、55 0.60 0.65 0.666 0.70 0.75 0.80 0.85 0.90 0.95 1.00 2.0 1.95 1.9 1.85 1.8 1.75 1.7 1.667 1.65 1.6 1.55 1.5 1.45 1.40 1.35 1.334 1.30 1.25 1.20 1.15 1.10 1.05 1.00 a It is essential to read these tables in conjunction with A.2. n K n K 0.05 0.10 0.15 0.20 0.25 0.38 0.72 1.02 1.28 1.50 0.30 0.35 0.4

47、0 0.45 0.50 1.68 1.82 1.92 1.98 2.00 a It is essential to read these tables in conjunction with A.2.8 blankBS5977-1:1981 BSI 01-1999 Publications referred to BS 648, Schedule of weights of building materials. BS 5628, Code of practice for use of masonry. BS 5628-1, Structural use of unreinforced mas

48、onry. BS 5628-2, Structural use of reinforced and prestressed masonry. BS 5628-3, Materials and components, design and workmanship. BS 6399, Design loading for buildings. BS 6399-1, Code of practice for dead and imposed loads. CP 3, Code of basic data for the design of buildings. CP 121, Walling. BS

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