1、Designation: D 5457 04aStandard Specification forComputing Reference Resistance of Wood-Based Materialsand Structural Connections for Load and Resistance FactorDesign1This standard is issued under the fixed designation D 5457; the number immediately following the designation indicates the year ofori
2、ginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONLoad and resistance factor design (LRFD) is a structural desi
3、gn method 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 prope
4、rty 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 wo
5、od-based 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
6、X1.2. Referenced Documents2.1 ASTM Standards:2D 9 Terminology Relating to WoodD 143 Test Methods for Small Clear Specimens of TimberD 198 Test Methods of Static Tests of Lumber in StructuralSizesD 1037 Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel MaterialsD 1761 Test
7、Methods for Mechanical Fasteners in WoodD 1990 Practice for Establishing Allowable Properties forVisually-Graded Dimension Lumber From In-Grade Testsof Full-Size SpecimensD 2718 Test Methods for Structural Panels in Planar Shear(Rolling Shear)D 2719 Test Methods for Structural Panels in ShearThrough
8、-the-ThicknessD 2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD 3043 Test Methods for Testing Structural Panels in Flex-ureD 3500 Test Methods for Structural Panels in TensionD 3501 Test Methods for Wood-Based Structural Panels inCompressionD 3737 Practice for Estab
9、lishing Allowable Properties forStructural Glued Laminated Timber (Glulam)D 4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialD 5055 Specification for Establishing and MonitoringStructural Capacities of Prefabricated Wood I-JoistsD 5456 Specification for Evaluatio
10、n of Structural Compos-ite Lumber ProductsE 105 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 D 9.3.1.1 coeffcient of
11、variation, CVwa relative measure ofvariability. For this specification, the calculation of CVwisbased on the shape parameter of the 2-parameter Weibulldistribution. It is not the traditional sample standard deviationof the data divided by the sample mean.1This specification is under the jurisdiction
12、 of ASTM Committee D07 on Woodand is the direct responsibility of Subcommittee D07.02 on Lumber and EngineeredWood Products.Current edition approved Nov. 1, 2004. Published November 2004. Originallyapproved in 1993. Last previous edition approved in 2004 as D 5457 - 04.2For referenced ASTM standards
13、, 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.3Available from The American Society of Civil Engineers (ASCE), 1801Alexander Bell Dr., Res
14、ton, VA 20191.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.2 data confidence factor, Va factor that is used toadjust member reference resistance for sample variability andsample size.3.1.3 distribution percentile, Rpthe value
15、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 consistingof all test
16、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 resistance to achieve
17、 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 which inferences are t
18、o be made. Both manufacturingand material source variability shall be considered. The prin-ciples of Practice E 105 shall be maintained. Practice D 2915provides methods for establishing a sampling plan. Specialattention is directed to sampling procedures in which thevariability is low and results ca
19、n 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 from multiple data
20、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 minimum sample s
21、ize 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 failedobservations is
22、 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 lower tail).Only
23、parameter estimation procedures designed specifically forlower 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 capacity of the pro
24、duct 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 section. Parameters
25、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 Reference Resistance
26、, 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 any percentileof
27、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 scale (h) paramet
28、ers 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 when determining
29、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 exact relationship o
30、f 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 thedistribution estimate
31、. 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.4Weibull, W., “A Statistical Theory of the Strength of Materials,” Proceedings o
32、fthe 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 Engineers, 1988.D 5457 04a26.6 Reliability Normalization Factor, KRThe reliabilityn
33、ormalization 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 scaling factor.
34、 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 target reliability in
35、dices 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 resistance valuesbase
36、d 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 Methods D 143, D
37、198, D 1037,D 1761, D 2718, D 2719, D 3043, D 3500, D 3501, and D 4761; PracticesD 1990 and D 3737; and Specifications D 5055 and D 5456.6.7.2 For standardization purposes, format conversion ref-erence resistance values shall be based on the arithmeticconversion at a specified reference condition th
38、at 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 load
39、 cases and load ratiosis minimized.6.7.3 Based on the same load factors and load ratio as thosegiven in 6.6, with an ASD load duration adjustment factor of1.15 and a LRFD time effect factor of 0.80, the formatconversion factor, KF, is as follows:KF52.16fs(4)6.7.4 Since ASD deformation-based compress
40、ion perpen-dicular to grain values are not subject to the duration of loadadjustment, the constant in the numerator of Eq 4 is 1.875 forthis property.6.7.5 Since neither ASD nor LRFD modulus of elasticityvalues are subject to duration of load or time effect adjust-ments, the constant in the numerato
41、r of Eq 4 is 1.5 whenmodulus of elasticity is used in a strength (rather than stiffness)calculation (such as stability).6.7.6 Since design capacities for shear walls or diaphragmsare based on a set of different reference conditions than thosegiven in 6.6, the constant in the numerator of Eq 4 is 1.6
42、 forthese assemblies.NOTE 5This revised constant is only intended to be applied to thedesign capacity of shear wall or diaphragm assembliesnot to the designof individual members or subcomponents of these assemblies. Theconstant in 6.7.3 is to be used for design of individual members orsubcomponents
43、of shear walls or diaphragms.6.7.7 The format conversion reference resistance is com-puted by multiplying the ASD resistance (based on normal10-year duration for members and connections) by KF.6.7.7.1 ExceptionThe format conversion reference resis-tance for shear walls and diaphragms is based on a s
44、hort-termduration.6Zahn, 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 R0.05, for Two-ParameterWeibull Distribution with 75 % ConfidenceACVwSample Size, n30 40 50 60 100 200 500 1000 2
45、000 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 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 0.8
46、7 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 0.98AInterpolation is permitted. For CVwvalues below 0.10, the values for 0.10 shallbe used.TABLE 2 Specified L
47、RFD Resistance Factors, fsApplication Property fsMember compressionA0.90bending, lateral buckling (stability) 0.85tension parallel 0.80shear, radial tension 0.75Connection all 0.65Shear Wall, diaphragm shear 0.80ACompression parallel-to-grain, compression perpendicular-to-grain, and bear-ing.TABLE 3
48、 Fifth-Percentile Based Reliability NormalizationFactors, KRCVw,%KRCompressionand BearingBendingTensionParallelShear(2.1basis)Shear(SCL,3.15basis)Shear(I-Joist,2.37basis)10 1.303 1.248 1.326 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
49、.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 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 1.071 1.138 1.214 0.809 1.07627 1.105 1.059 1.125 1.200 0.800 1.06328 1.084 1.
