ASTM E73-1983(2007) Standard Practice for Static Load Testing of Truss Assemblies《桁架组件的静态载荷试验》.pdf

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1、Designation: E 73 83 (Reapproved 2007)Standard Practice forStatic Load Testing of Truss Assemblies1This standard is issued under the fixed designation E 73; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.

2、 A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice is intended as a guide for use in the testingof truss assemblies fabricated from all types of constructionmaterials.

3、While the practice may be used for the testing of avariety of assemblies, it is primarily intended to be used in thetesting of those trusses designed to be spaced at 1.2 m (48 in.)centers or greater. It can be used, but it is not normallyintended, for the testing of wood residential trussed rafters.

4、Either proof tests or tests to destruction may be run.1.2 LimitationsIt is not intended that this practice be usedfor routine quality control testing.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this

5、standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Section 7.2. Referenced Documents2.1 ASTM Standards:2E 196 Practice for Gravity Load Testing of Floors and LowSlope RoofsE 575 Pr

6、actice for Reporting Data from Structural Tests ofBuilding Constructions, Elements, Connections, and As-sembliesE 631 Terminology of Building Constructions3. Terminology3.1 trussa coplanar system of structural elements joinedtogether at their ends usually to construct a series of trianglesthat form

7、a stable beam-like framework.3.2 static loada load or series of loads that are supportedby or are applied to a structure so gradually that forces causedby change in momentum of the load and structural elementscan be neglected and all parts of the system at any instant areessentially in equilibrium.3

8、.3 For other definitions in this practice, see TerminologyE 631.4. Summary of Practice4.1 This practice outlines the procedures to be followed inthe static load testing of major load carrying truss assemblies.While the procedure tells what to do, it does not tell the testingagency how to do it. This

9、 leaves the selection of the test fixtureand loading medium to the discretion of the testing agency.Materials selection, sampling, conditioning, fabrication, testprocedures, and report requirements are covered.4.2 Two types of tests may be conducted using this practice:4.2.1 Proof TestsA proof test

10、is frequently made toprovide assurance that the truss will support a stated load or todetermine the deformations and structural response under aspecified loading.4.2.2 Test to FailureIn testing to failure, more detailedinformation is generally desired such as ultimate load carryingcapacity, total lo

11、ad-deflection history, yield point, connectionperformance, factor of safety, etc.4.2.3 If desired, either type of test may be extended toinclude a determination of the magnitude and distribution ofthe stresses in the members and connections in order to permita more comprehensive analysis of the trus

12、s performance.5. Significance and Use5.1 This practice provides a guide to any individual, group,agency, or code body on the methods of test for trussassemblies fabricated from all types of construction materials.Sample size is generally kept to a minimum to reduce costs.The methods may be used to a

13、pply proof loads to an assemblyor to test it to failure. Information obtained includes strengthand stiffness data, and if assemblies are tested to their ultimateload carrying capacity, the failure method or mechanism can beobserved.6. Test Apparatus6.1 GeneralWhile the methods described in this proc

14、e-dure are best suited to tests of trusses before installation in astructure, they can also be applied to the testing of trusses afterinstallation. In the former case, the truss may be tested in eithera vertical position (normal or inverted) or in a horizontal1This practice is under the jurisdiction

15、 of ASTM Committee E06 on Perfor-mance of Buildings and is the direct responsibility of Subcommittee E06.11 onHorizontal and Vertical Structures/Structural Performance of Completed Structures.Current edition approved April 1, 2007. Published April 2007. Originallyapproved in 1948. Last previous edit

16、ion approved in 2002 as E 73 - 83 (2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM Inte

17、rnational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.position. Additional loadings must be applied to trusses testedin an inverted or horizontal position to compensate for theeffect of dead loads and gravity. Regardless of the orientationof the truss in the

18、test fixture, the fixture and load applicationmeans shall be designed with an ample margin of safety toensure that it is the test specimen that is being tested and notthe test fixture. More information on the testing of componentsin existing structures is contained in Practice E 196.6.2 Supports and

19、 Reactions:6.2.1 The reaction supports shall provide sufficient clear-ance above the ground or restraint frame to allow for normaldisplacements, ease of loading, instrumentation, and provideroom for observations and measurements. Supports shall haveadequate strength and stiffness to resist deformati

20、ons duringtests.6.2.2 Support reaction hardware shall be typical of thatplanned for use in the completed structure or as required tosatisfy the intent of the tests. In a single truss test, frequentlythe support at one end will allow rotation but not translation (arocker) and the other will allow bot

21、h rotation and translation (aroller) so as not to induce additional unintentional secondarystresses into the test truss as it deforms under load.6.2.3 Where lateral support is used, it shall not interferewith the free in-plane displacement of the truss assembly. Thetest trusses shall not be laterall

22、y supported in a manner that willexceed that intended in a typical installation. Trusses tested inpairs shall be laterally braced and sheathed in a typical manner.Lateral bracing between trusses tested in pairs shall be installedin a manner to prevent both trusses from buckling together.Care shall b

23、e taken when testing trusses horizontally to keepthe test truss flat to minimize any adverse lateral displacementcaused by gravity.6.3 Loading Devices:6.3.1 The loading devices shall result in the desired trussloading situation regardless of whether uniform, concentrated,or a combination of both. Th

24、e system shall be such as to allowthe application of loads during the test to approximate theoverall intended in-service load distribution. Care should betaken to avoid eccentrically applied loads unless this type ofloading is desired.6.3.2 Vertical loads may be applied in the form of deadweight thr

25、ough bearing, suspension, or jacking arrangements.Horizontal loads are usually applied by some form of jackingarrangement directly in-plane or by using a system of cablesand pulleys with dead weights or hydraulic cylinders. Theloading system should have provisions for applying unbal-anced loads when

26、 this type of loading can be critical to trussperformance (see 9.4). Uplift forces such as those caused bywind loads may be simulated by reversing the direction of theapplied gravity loads; or if the fixture will permit it, testing thetruss upside down. It is preferable to test the truss in itsnorma

27、lly installed orientation in order to more typically allowfor the uplift forces working against gravity forces.6.3.3 When loads are to be applied using dead weight, suchitems as sand, masonry units, iron or lead ingots, boxed nails,roll roofing, water or boxed fireplace logs have been success-fully

28、employed as a loading medium. The arrangement of deadload material shall be such as to prevent any arching action thatcan seriously alter the intended load pattern. When water isused, care shall be taken to compartmentalize the water in cellsto prevent a non-uniform load as the truss and elements de

29、flect.Air bags reacting against restraint frames have also been used.6.4 Load and Deflection Measuring Devices6.4.1 Load Measuring DevicesLoads may be measuredusing one or more of the following devices. Pressure gages orhydraulic load cells can be incorporated into a hydraulicloading system. These d

30、evices must be calibrated with thejacks or cylinders at different positions of piston travel toensure a true loading history. Spring dynamometers, electronicload cells, or the weighing tables of universal testing machineshave also been successfully used. The load measuring device ordevices used shal

31、l be capable of measuring loads to anaccuracy of 6 2 % of design load.6.4.2 Deflection Measuring Devices:6.4.2.1 Deflection readings may be taken in a variety ofways. One of the simplest methods is by the use of a taut wireor mono-filament line stretched between supports in combina-tion with a mirro

32、r-scale located at the desired deflectionmeasuring points. Such a device avoids any magnification ofdeflection readings due to a settlement of supports duringloading. When the taut wire method is used, care must be takento ensure that the wire will remain under tension during theentire test. This ca

33、n be accomplished by incorporating a springinto the line or by letting one end run over a pulley with aweight attached to the line. Deflections are read on a scale witha mirror backing. The mirror-scale deflection measuring deviceis read by visually lining up the top of the wire with its imageon the

34、 mirror and then reading the scale.6.4.2.2 Other commonly used devices are such things asdirect reading micrometer dial gages, optical levels used toread scales attached to the truss, linearly variable differentialtransformers (LVDT), or a combination of flexible wire at-tached at deflection points

35、and monitored remotely through asystem of pulleys attached to dial gages. Deflection readingsand measuring devices shall have an accuracy of 6 2%ofdesign load deflection.6.4.3 Strain MeasurementsStrain measurements may betaken on truss elements using electrical or mechanical straingages. Approximate

36、 stress distribution and magnitude may beobserved by the application of special brittle lacquers to theareas of interest. All of these measurements should be made bypersonnel experienced in the application and operation of themethods employed on the material being tested.6.5 Typical SetupsSome sugge

37、sted setups for runningtruss tests are shown in Figs. 1-3.7. Hazards7.1 Full-scale load tests of any large size specimen such asa truss can be hazardous to the individuals performing orobserving the tests, and also damage the testing fixtures or thestructure housing the test setup due to a sudden re

38、lease ofstored energy at failure. Care should be exercised in thepreparation of the test setup to ensure that the failure of a testspecimen will not result in a secondary collapse of a structuralelement not involved in the test.E 73 83 (2007)28. Test Specimens8.1 Number of SpecimensThe number of sim

39、ilar trussesthat should be tested will vary with the desired precision andreliability of the information to be obtained and with thepurpose of the text. Where only approximate values are desiredor the assembly is large and contains many elements, a singletest may suffice. Where more precise and stat

40、istically reliabledata are required, a minimum of three or more tests arepreferred. The final number will be controlled by the purposeof the tests, and as agreed upon by the sponsor, testing agencyor regulatory agency, if any is involved.8.2 Materials:8.2.1 Truss assembly elements, connectors, and c

41、onnectionsshall be typical of those intended for use in the final product oras required to satisfy the intent of the tests.8.2.2 Truss materials that are moisture, time, temperature orotherwise sensitive to curing or conditioning, which can affectthe performance of the test assembly, shall be repres

42、entative of(a) Truss assembly with panel point loading.FIG. 1 Trusses Set Vertical, in Normal PositionFIG. 2 Truss Set Vertical, in Inverted PositionE 73 83 (2007)3materials intended for use in the final assembly or as requiredto meet the intent of the tests.8.3 Fabrication:8.3.1 Fabrication of the

43、test specimens shall be typical ofthat intended for the finished product or as necessary to satisfythe purpose of the tests. Where “standard” conditions arerequired at the time of test, such as a particular curing or agingtime, moisture content, etc., the truss materials and the fabri-cated assembli

44、es shall be conditioned, stored and handled in amanner to achieve them.8.3.2 Connections shall be made in accordance with goodpractice following the recommendations of the manufacturer ofthe connectors or connecting material involved.9. Loading Procedures9.1 Load Increments:9.1.1 Although the load i

45、ncrements may vary with the intentof the test, satisfactory load-response data can usually beobtained if each of the first four increments of load does notexceed 25 % of the total design live load and any additionalload increments do not exceed 50 % of the design live load.Load shall be slowly appli

46、ed to the truss assembly so as toprovide a static loading condition. This is particularly impor-tant with materials that are sensitive to time under load.9.1.2 The above mentioned load increments apply to bothuniform and concentrated loads.9.2 Deflection Measurements:9.2.1 As a minimum, take deflect

47、ion measurements alongthe bottom chord at midspan and at quarter points.9.2.2 When deflection measuring systems that do not com-pensate for support settlement are used, measurement ofsupport displacement under load is needed to obtain anaccurate load-deflection response and recovery after the re-mov

48、al of load.9.3 Duration of Load ApplicationExcept in the instancesof impact and racking tests, after each increment of load isapplied, the load level shall be maintained as constant aspossible for a period of five minutes (see 9.3.1). Deformationreadings shall be taken as soon as practical after loa

49、d applica-tion, at the end of the 5-min period under constant load, andimmediately and at the end of the 5-min period after any partialor complete load release. Initial and 5-min readings shall beplotted in the form of load-deformation curves. Completeload-deformation-time records shall be maintained throughoutthe test. If application of a given load is required for a certainperiod, such as 24 h, deformation readings shall be taken at thebeginning, at intervals during this period, and at the end of thisperiod, to allow the satisfactory plotting of a time-deformationcurve f