1、Designation: D5457 12D5457 15Standard 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
2、oforiginal 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
3、design 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 p
4、roperty 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 the reference resistance
5、of wood-based materials and structuralconnections for use in load and resistance factor design (LRFD). The reference resistance derived from this specification appliesto the design of structures addressed by the load combinations in ASCE 7-10.1.2 A commentary to this specification is provided in App
6、endix X1.2. Referenced Documents2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based ProductsD143 Test Methods for Small Clear Specimens of TimberD198 Test Methods of Static Tests of Lumber in Structural SizesD1037 Test Methods for Evaluating Properties of Wood-Base Fiber and Particle
7、Panel MaterialsD1761 Test Methods for Mechanical Fasteners in WoodD1990 Practice for EstablishingAllowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-SizeSpecimensD2718 Test Methods for Structural Panels in Planar Shear (Rolling Shear)D2719 Test Methods for Structura
8、l Panels in Shear Through-the-ThicknessD2915 Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based ProductsD3043 Test Methods for Structural Panels in FlexureD3500 Test Methods for Structural Panels in TensionD3501 Test Methods for Wood-Based Structural Panels in CompressionD373
9、7 Practice for Establishing Allowable Properties for Structural Glued Laminated Timber (Glulam)D4761 Test Methods for Mechanical Properties of Lumber and Wood-Base Structural MaterialD5055 Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I-JoistsD5456 Specifi
10、cation for Evaluation of Structural Composite Lumber ProductsE105 Practice for Probability Sampling of Materials1 This specification is under the jurisdiction ofASTM Committee D07 on Wood and is the direct responsibility of Subcommittee D07.02 on Lumber and Engineered WoodProducts.Current edition ap
11、proved May 1, 2012May 1, 2015. Published July 2012June 2015. Originally approved in 1993. Last previous edition approved in 20102012 asD5457 - 10.D5457 - 12. DOI: 10.1520/D5457-12.10.1520/D5457-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at
12、 serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous vers
13、ion. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM Internation
14、al, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 ASCE Standard:3ASCE 7-10 Minimum Design Loads for Buildings and Other Structures3. Terminology3.1 Definitions:3.1.1 For general definitions of terms related to wood, refer to Terminology D9.3.1.2 coeffcient o
15、f variation, CVwa relative measure of variability. For this specification, the calculation of CVw is based onthe shape parameter of the 2-parameter Weibull distribution. It is not the traditional sample standard deviation of the data dividedby the sample mean.3.1.3 data confidence factor, a factor t
16、hat is used to adjust member reference resistance for sample variability and samplesize.3.1.4 distribution percentile, Rpthe value of the distribution associated with proportion, p, of the cumulative distributionfunction.3.1.5 format conversion factor, KFa factor applied to convert resistance from t
17、he allowable stress design (ASD) format to theLRFD format.3.1.6 lower taila portion of an ordered data set consisting of all test specimens with the lowest property values (for example,lowest strengths).3.1.7 reference resistance, Rnthe value used in LRFD equations to represent member resistance (th
18、at is, strength or capacity).3.1.8 reliability normalization factor, KRa factor used to establish the reference resistance to achieve a target reliability indexfor a reference set of conditions.3.1.9 resistance factora factor applied to the resistance side of the LRFD equation.4. Sampling4.1 Samples
19、 selected for analysis and implementation with this specification shall be representative of the population aboutwhich inferences are to be made. Both manufacturing and material source variability shall be considered. The principles of PracticeE105 shall be maintained. Practice D2915 provides method
20、s for establishing a sampling plan. Special attention is directed tosampling procedures in which the variability is low and results can be influenced significantly by manufacturing variables. It isessential that the sampling plan address the relative magnitude of the sources of variability.4.1.1 Dat
21、a generated from a quality control program shall be acceptable if the criteria of 4.1 are maintained.4.1.2 When data from multiple data sets are compiled or grouped, the criteria used to group such data shall be in keeping withthe provisions of 4.1. When such procedures are available in applicable p
22、roduct standards, they shall be used.4.2 Sample Size:4.2.1 For data sets in which all specimens are tested to failure, the minimum sample size shall be 30.NOTE 1The confidence with which population properties can be estimated decreases with decreasing sample size. For sample sizes less than 60,extre
23、me care must be taken during sampling to ensure a representative sample.4.2.2 For lower tail data sets, a minimum of 60 failed observations is required for sample sizes of n = 600 or less. (Thisrepresents at least the lower 10 % of the distribution.) For sample sizes greater than 600, a minimum of t
24、he lowest 10 % of thedistribution is required (for example, sample size, n = 720, 0.10 (720) = 72 failed test specimens in the lower tail). Only parameterestimation procedures designed specifically for lower tail data sets shall be used (see Appendix X2).5. Testing5.1 Testing shall be conducted in a
25、ccordance with appropriate standard testing procedures. The intent of the testing shall be todevelop data that represent the capacity of the product in service.5.2 Periodic Property AssessmentPeriodic testing is recommended to verify that the properties of production material remainrepresentative of
26、 published properties.6. Reference Resistance for LRFD6.1 The derivation of LRFD reference resistance is addressed in this section. Parameters required for the derivation of referenceresistance are also presented. These parameters include the distribution percentile, coefficient of variation, data c
27、onfidence factor,and reliability normalization factor. An example derivation of reference resistance is provided in X1.7.6.2 Reference Resistance, RnThe following equation establishes reference resistance for LRFD:Rn 5Rp 33KR (1)3 Available from The American Society of Civil Engineers (ASCE), 1801 A
28、lexander Bell Dr., Reston, VA 20191.D5457 152where:Rp = distribution percentile estimate, = 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 percentile of a two-parameter Weibull distribution.
29、 The percentile of interestdepends on the property being estimated.Rp 52ln12p!#1/ (2)where: = Weibull scale parameter,p = percentile of interest expressed as a decimal (for example, 0.05), and = Weibull shape parameter.6.3.2 The shape () and scale () parameters of the two-parameter Weibull distribut
30、ion shall be established to define thedistribution of the material resistance.4 Algorithms for common estimation procedures are provided in Appendix X2.6.4 Coeffcient of Variation, CVwThe coefficient of variation of the material is necessary when determining the data confidencefactor, , and the reli
31、ability normalization factor, KR. The CVw can be estimated from the shape parameter of the Weibulldistribution as follows:CVw20.92 (3)NOTE 2The above approximation is within 1 % of the exact solution for CVw values between 0.09 and 0.50. An exact relationship of CVw and isshown in Appendix X3.6.5 Da
32、ta Confidence Factor, The data confidence factor, , accounts for uncertainty associated with data sets.5 This factor,which is a function of coefficient of variation, sample size, and reference percentile, is applied as a multiplier on the distributionestimate. Table 1 provides data confidence factor
33、s appropriate for lower fifth-percentile estimates.NOTE 3When a distribution tolerance limit is developed on a basis consistent with , the data confidence factor is taken as unity.6.6 Reliability Normalization Factor, KRThe reliability normalization factor, KR, is used to adjust the distribution est
34、imate (forexample, R0.05) to achieve a target reliability index. The reliability normalization factor is the ratio of the computed resistancefactor, c (X1.7), to the specified resistance factor, s (Table 2), adjusted by a scaling factor. This adjustment factor is a functionof CVw and is generated fo
35、r specific target reliability indices. The KR values presented in Table 3 represent resistance factors (c)computed at a live-to-dead load ratio of 3. Computations for determining reliability normalization factors for target reliabilityindices greater than = 2.4 are contained in Zahn.66.7 Format Conv
36、ersion:6.7.1 As an alternative to the use of KR, in which one chooses to adjust the design values to achieve a stated reliability indexunder the reference load conditions, it is permissible to generate LRFD reference resistance values based on format conversionfrom code-recognized allowable stress d
37、esign (ASD). It shall not be claimed that reference resistance values generated in thismanner achieve a stated reliability index.4 Weibull, W., “A Statistical Theory of the Strength of Materials,” Proceedings of the Royal Swedish Institute of Engineering Research, Stockholm, Sweden, Report No.151, 1
38、939, pp. 145.5 Load and Resistance Factor Design for Engineered Wood ConstructionA Pre-Standard Report, American Society of Civil Engineers, 1988.6 Zahn, J., FORTRAN Programs for Reliability Analysis, USDA Forest Service, FPL GTR-72, Forest Products Laboratory, Madison, WI, 1992.TABLE 1 Data Confide
39、nce Factor, on R0.05, for Two-ParameterWeibull Distribution with 75 % ConfidenceACVw Sample 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.
40、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 0.87 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.
41、90 0.94 0.95 0.97 0.98A Interpolation is permitted. For CVw values below 0.10, the values for 0.10 shallbe used.D5457 153NOTE 4Examples of standards that are used to generate code-recognized ASD values include Test Methods D143, D198, D1037, D1761, D2718,D2719, D3043, D3500, D3501, and D4761; Practi
42、ces D1990 and D3737; and Specifications D5055 and D5456.6.7.2 For standardization purposes, format conversion reference resistance values shall be based on the arithmetic conversionat a specified reference condition that results from the calibration (defined as providing an identical required sectio
43、n modulus,cross-sectional area, allowable load capacity, and so forth) of basic ASD and LRFD equations. The specified reference conditionshall be chosen such that changes in design capacity over the range of expected load cases and load ratios is minimized.6.7.3 Values of the format conversion facto
44、r, KF, are given in Table 4.TABLE 2 Specified LRFD Resistance Factors, sApplication Property sMember compressionA 0.90bending, lateral buckling (stability) 0.85tension parallel 0.80shear, radial tension 0.75Connection all 0.65Shear Wall, diaphragm shear 0.80A Compressionparallel-to-grain,compression
45、perpendicular-to-grain,andbearing.TABLE 3 Fifth-Percentile Based Reliability NormalizationFactors, KRCVw,%KRCompressionand Bearing BendingTensionParallelShear(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 1.2
46、53 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 1.274 1.359 0.906 1.20419 1.237 1.185 1.259 1.343 0.895 1.19020 1.219
47、 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
48、.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 2.88AShear, Radial Tension 2.88Radial Tension 2.88Connections 3.32Late
49、ral Buckling (Stability) 1.76Compression Perpendicular to Grain 1.67Shear Wall and Diaphragm Shear 2.00AShear Wall and Diaphragm Shear 2.00BAThe value of the format conversion factor is 2.00 where shear is not subject toload duration or time effect adjustments (e.g., rolling shear in cross-laminatedtimber).B TheThe 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 theseassemb
