1、Designation: D5457 10Standard Specification forComputing Reference Resistance of Wood-Based Materialsand Structural Connections for Load and Resistance FactorDesign1This standard is issued under the fixed designation D5457; the number immediately following the designation indicates the year oforigin
2、al adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONLoad and resistance factor design (LRFD) is a structural design m
3、ethod that uses concepts fromreliability theory and incorporates them into a procedure usable by the design community. The basicdesign equation requires establishing a reference resistance based on several material propertyparameters. A standard method for calculating the required material property
4、input data is critical sothat all wood-based structural materials can be treated equitably. This specification provides theprocedures that are required for the generation of reference resistance for LRFD.1. Scope1.1 This specification covers procedures for computing thereference resistance of wood-b
5、ased materials and structuralconnections for use in load and resistance factor design(LRFD). The reference resistance derived from this specifica-tion applies to the design of structures addressed by the loadcombinations in ASCE 7-02.1.2 A commentary to this specification is provided inAppendix X1.2
6、. Referenced Documents2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-uctsD143 Test Methods for Small Clear Specimens of TimberD198 Test Methods of Static Tests of Lumber in StructuralSizesD1037 Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel Mate
7、rialsD1761 Test Methods for Mechanical Fasteners in WoodD1990 Practice for Establishing Allowable Properties forVisually-Graded Dimension Lumber from In-Grade Testsof Full-Size SpecimensD2718 Test Methods for Structural Panels in Planar Shear(Rolling Shear)D2719 Test Methods for Structural Panels in
8、 ShearThrough-the-ThicknessD2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD3043 Test Methods for Structural Panels in FlexureD3500 Test Methods for Structural Panels in TensionD3501 Test Methods for Wood-Based Structural Panels inCompressionD3737 Practice for Establ
9、ishing Allowable Properties forStructural Glued Laminated Timber (Glulam)D4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialD5055 Specification for Establishing and Monitoring Struc-tural Capacities of Prefabricated Wood I-JoistsD5456 Specification for Evaluation
10、of Structural CompositeLumber ProductsE105 Practice for Probability Sampling of Materials2.2 ASCE Standard:3ASCE 7-02 Minimum Design Loads for Buildings andOther Structures3. Terminology3.1 DefinitionsFor general definitions of terms related towood, refer to Terminology D9.3.1.1 coeffcient of variat
11、ion, CVwa relative measure ofvariability. For this specification, the calculation of CVwis1This specification is under the jurisdiction of ASTM Committee D07 on Woodand is the direct responsibility of Subcommittee D07.02 on Lumber and EngineeredWood Products.Current edition approved Sept. 1, 2010. P
12、ublished September 2010. Originallyapproved in 1993. Last previous edition approved in 2004 as D5457 - 04A. DOI:10.1520/D5457-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informati
13、on, refer to the standards Document Summary page onthe ASTM website.3Available from The American Society of Civil Engineers (ASCE), 1801Alexander Bell Dr., Reston, VA 20191.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.based on the
14、 shape parameter of the 2-parameter Weibulldistribution. It is not the traditional sample standard deviationof the data divided by the sample mean.3.1.2 data confidence factor, Va factor that is used toadjust member reference resistance for sample variability andsample size.3.1.3 distribution percen
15、tile, Rpthe value of the distribu-tion associated with proportion, p, of the cumulative distribu-tion function.3.1.4 format conversion factor, KFa factor applied toconvert resistance from the allowable stress design (ASD)format to the LRFD format.3.1.5 lower taila portion of an ordered data set cons
16、istingof all test specimens with the lowest property values (forexample, lowest strengths).3.1.6 reference resistance, Rnthe value used in LRFDequations to represent member resistance (that is, strength orcapacity).3.1.7 reliability normalization factor, KRa factor used toestablish the reference res
17、istance to achieve a target reliabilityindex for a reference set of conditions.3.1.8 resistance factora factor applied to the resistanceside of the LRFD equation.4. Sampling4.1 Samples selected for analysis and implementation withthis specification shall be representative of the populationabout whic
18、h inferences are to be made. Both manufacturingand material source variability shall be considered. The prin-ciples of Practice E105 shall be maintained. Practice D2915provides methods for establishing a sampling plan. Specialattention is directed to sampling procedures in which thevariability is lo
19、w and results can be influenced significantly bymanufacturing variables. It is essential that the sampling planaddress the relative magnitude of the sources of variability.4.1.1 Data generated from a quality control program shall beacceptable if the criteria of 4.1 are maintained.4.1.2 When data fro
20、m multiple data sets are compiled orgrouped, the criteria used to group such data shall be inkeeping with the provisions of 4.1. When such procedures areavailable in applicable product standards, they shall be used.4.2 Sample Size:4.2.1 For data sets in which all specimens are tested tofailure, the
21、minimum sample size shall be 30.NOTE 1The confidence with which population properties can beestimated decreases with decreasing sample size. For sample sizes lessthan 60, extreme care must be taken during sampling to ensure arepresentative sample.4.2.2 For lower tail data sets, a minimum of 60 faile
22、dobservations is required for sample sizes of n = 600 or less.(This represents at least the lower 10 % of the distribution.) Forsample sizes greater than 600, a minimum of the lowest 10 %of the distribution is required (for example, sample size,n = 720, 0.10 (720) = 72 failed test specimens in the l
23、owertail). Only parameter estimation procedures designed specifi-cally for lower tail data sets shall be used (see Appendix X2).5. Testing5.1 Testing shall be conducted in accordance with appropri-ate standard testing procedures. The intent of the testing shallbe to develop data that represent the c
24、apacity of the product inservice.5.2 Periodic Property AssessmentPeriodic testing is rec-ommended to verify that the properties of production materialremain representative of published properties.6. Reference Resistance for LRFD6.1 The derivation of LRFD reference resistance is ad-dressed in this se
25、ction. Parameters required for the derivationof reference resistance are also presented. These parametersinclude the distribution percentile, coefficient of variation, dataconfidence factor, and reliability normalization factor. Anexample derivation of reference resistance is provided in X1.7.6.2 Re
26、ference Resistance, RnThe following equation es-tablishes reference resistance for LRFD:Rn5 Rp3V3KR(1)where:Rp= distribution percentile estimate,V = data confidence factor, andKR= reliability normalization factor.6.3 Distribution Percentile Estimate, Rp:6.3.1 Eq 2 is intended to be used to calculate
27、 any percentileof a two-parameter Weibull distribution. The percentile ofinterest depends on the property being estimated.Rp5h2ln1 2 p!#1/a(2)where:h = Weibull scale parameter,p = percentile of interest expressed as a decimal (forexample, 0.05), anda = Weibull shape parameter.6.3.2 The shape (a) and
28、 scale (h) parameters of the two-parameter Weibull distribution shall be established to definethe distribution of the material resistance.4Algorithms forcommon estimation procedures are provided in Appendix X2.6.4 Coeffcient of Variation, CVwThe coefficient of varia-tion of the material is necessary
29、 when determining the dataconfidence factor, V, and the reliability normalization factor,KR. The CVwcan be estimated from the shape parameter of theWeibull distribution as follows:CVw a20.92(3)NOTE 2The above approximation is within 1 % of the exact solutionfor CVwvalues between 0.09 and 0.50. An ex
30、act relationship of CVwanda is shown in Appendix X3.6.5 Data Confidence Factor, VThe data confidence fac-tor, V, accounts for uncertainty associated with data sets.5Thisfactor, which is a function of coefficient of variation, samplesize, and reference percentile, is applied as a multiplier on the4We
31、ibull, W., “AStatistical Theory of the Strength of Materials,” Proceedings ofthe Royal Swedish Institute of Engineering Research , Stockholm, Sweden, ReportNo. 151, 1939, pp. 145.5Load and Resistance Factor Design for Engineered Wood ConstructionAPre-Standard Report, American Society of Civil Engine
32、ers, 1988.D5457 102distribution estimate. Table 1 provides data confidence factorsappropriate for lower fifth-percentile estimates.NOTE 3When a distribution tolerance limit is developed on a basisconsistent with V, the data confidence factor is taken as unity.6.6 Reliability Normalization Factor, KR
33、The reliabilitynormalization factor, KR, is used to adjust the distributionestimate (for example, R0.05) to achieve a target reliabilityindex. The reliability normalization factor is the ratio of thecomputed resistance factor, fc(X1.7), to the specified resis-tance factor, fs(Table 2), adjusted by a
34、 scaling factor. Thisadjustment factor is a function of CVwand is generated forspecific target reliability indices. The KRvalues presented inTable 3 represent resistance factors (fc) computed at a live-to-dead load ratio of 3. Computations for determining reliabil-ity normalization factors for targe
35、t reliability indices greaterthan b = 2.4 are contained in Zahn.66.7 Format Conversion:6.7.1 As an alternative to the use of KR, in which onechooses to adjust the design values to achieve a statedreliability index under the reference load conditions, it ispermissible to generate LRFD reference resis
36、tance valuesbased on format conversion from code-recognized allowablestress design (ASD). It shall not be claimed that referenceresistance values generated in this manner achieve a statedreliability index.NOTE 4Examples of standards that are used to generate code-recognized ASD values include Test M
37、ethods D143, D198, D1037,D1761, D2718, D2719, D3043, D3500, D3501, and D4761; PracticesD1990 and D3737; and Specifications D5055 and D5456.6.7.2 For standardization purposes, format conversion ref-erence resistance values shall be based on the arithmeticconversion at a specified reference condition
38、that results fromthe calibration (defined as providing an identical requiredsection modulus, cross-sectional area, allowable load capacity,and so forth) of basic ASD and LRFD equations. The specifiedreference condition shall be chosen such that changes in designcapacity over the range of expected lo
39、ad cases and load ratiosis minimized.6.7.3 Values of the format conversion factor, KF, are givenin Table 4.6.7.4 The format conversion reference resistance is com-puted by multiplying the ASD resistance by KF. For membersand connections, the ASD resistance is based on a normal(10-year) load duration
40、. For shear walls and diaphragms, theASD resistance is based on a 10-minute load duration.6.7.5 For lateral buckling (stability) and compression per-pendicular to grain, the value of KFis based on the assumptionthat neither the ASD nor LRFD resistance values are subject toduration of load or time ef
41、fect adjustments.6.7.6 Format Conversion ExampleAn ASD bolt designvalue for a single shear connection is 800 lbf (based on normal6Zahn, J., FORTRAN Programs for Reliability Analysis , USDA Forest Service,FPL GTR-72, Forest Products Laboratory, Madison, WI, 1992.TABLE 1 Data Confidence Factor, V on R
42、0.05, for Two-ParameterWeibull Distribution with 75 % ConfidenceACVwSample Size, n30 40 50 60 100 200 500 1000 2000 50000.10 0.95 0.95 0.96 0.96 0.97 0.98 0.99 0.99 0.99 1.00.15 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 0.99 0.990.20 0.89 0.91 0.92 0.93 0.94 0.96 0.98 0.98 0.99 0.990.25 0.87 0.88 0.90
43、 0.91 0.93 0.95 0.97 0.98 0.98 0.990.30 0.84 0.86 0.88 0.89 0.92 0.94 0.96 0.97 0.98 0.990.35 0.81 0.84 0.86 0.87 0.90 0.93 0.96 0.97 0.98 0.990.40 0.79 0.81 0.84 0.85 0.89 0.92 0.95 0.96 0.97 0.980.45 0.76 0.79 0.82 0.85 0.87 0.91 0.94 0.96 0.97 0.980.50 0.73 0.77 0.80 0.81 0.86 0.90 0.94 0.95 0.97
44、 0.98AInterpolation is permitted. For CVwvalues below 0.10, the values for 0.10 shallbe used.TABLE 2 Specified LRFD Resistance Factors, fsApplication Property fsMember compressionA0.90bending, lateral buckling (stability) 0.85tension parallel 0.80shear, radial tension 0.75Connection all 0.65Shear Wa
45、ll, diaphragm shear 0.80ACompression parallel-to-grain, compression perpendicular-to-grain, and bear-ing.TABLE 3 Fifth-Percentile Based Reliability NormalizationFactors, KRCVw,%KRCompressionand BearingBendingTensionParallelShear(2.1basis)Shear(SCL,3.15basis)Shear(I-Joist,2.37basis)10 1.303 1.248 1.3
46、26 1.414 0.943 1.25311 1.307 1.252 1.330 1.419 0.946 1.25712 1.308 1.253 1.331 1.420 0.947 1.25813 1.306 1.251 1.329 1.418 0.945 1.25614 1.299 1.244 1.322 1.410 0.940 1.24915 1.289 1.235 1.312 1.400 0.933 1.24016 1.279 1.225 1.302 1.388 0.926 1.23017 1.265 1.212 1.288 1.374 0.916 1.21718 1.252 1.199
47、 1.274 1.359 0.906 1.20419 1.237 1.185 1.259 1.343 0.895 1.19020 1.219 1.168 1.241 1.324 0.882 1.17321 1.204 1.153 1.225 1.307 0.871 1.15822 1.186 1.136 1.207 1.287 0.858 1.14123 1.169 1.120 1.190 1.269 0.846 1.12524 1.152 1.104 1.173 1.251 0.834 1.10925 1.135 1.087 1.155 1.232 0.821 1.09226 1.118 1
48、.071 1.138 1.214 0.809 1.07627 1.105 1.059 1.125 1.200 0.800 1.06328 1.084 1.038 1.103 1.176 0.784 1.04229 1.066 1.021 1.085 1.157 0.771 1.02530 1.049 1.005 1.068 1.139 0.759 1.009TABLE 4 Format Conversion Factor, KFProperty KFCompression Parallel to Grain 2.40Bending 2.54Tension Parallel 2.70Shear,
49、 Radial Tension 2.88Connections 3.32Lateral Buckling (Stability) 1.76Compression Perpendicular to Grain 1.67Shear Wall and Diaphragm Shear 2.00AAThe format conversion factor for shear wall and diaphragm shear is onlyintended to be applied to the design capacity of shear wall or diaphragmassemblies, not to the design of individual members or subcomponents of theseassemblies.D5457 10310-year load duration). From Table 4, the format conversionfactor is 3.32. The corresponding LRFD bolt reference resis-tance value is as follows:Rn5 3.32 3 800 (4)Rn5 2658 lbf6.7.
