ASTM D245-2006 Standard Practice for Establishing Structural Grades and Related Allowable Properties for Visually Graded Lumber《确立目测分等木材的结构等级及有关允许性能的标准规程》.pdf
《ASTM D245-2006 Standard Practice for Establishing Structural Grades and Related Allowable Properties for Visually Graded Lumber《确立目测分等木材的结构等级及有关允许性能的标准规程》.pdf》由会员分享,可在线阅读,更多相关《ASTM D245-2006 Standard Practice for Establishing Structural Grades and Related Allowable Properties for Visually Graded Lumber《确立目测分等木材的结构等级及有关允许性能的标准规程》.pdf(16页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: D 245 06Standard Practice forEstablishing Structural Grades and Related AllowableProperties for Visually Graded Lumber1This standard is issued under the fixed designation D 245; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This practice (1
3、,2)2covers the basic principles forestablishing related unit stresses and stiffness values for designwith visually-graded solid sawn structural lumber. This prac-tice starts with property values from clear wood specimens andincludes necessary procedures for the formulation of structuralgrades of any
4、 desired strength ratio.1.2 The grading provisions used as illustrations herein arenot intended to establish grades for purchase, but rather toshow how stress-grading principles are applied. Detailed grad-ing rules for commercial stress grades which serve as purchasespecifications are established an
5、d published by agencies whichformulate and maintain such rules and operate inspectionfacilities covering the various species.1.3 The material covered in this practice appears in thefollowing order:SectionScope 1Significance and Use 3Basic Principles of Strength Ratios 4Estimation and Limitation of G
6、rowth Characteristics 5Allowable Properties for Timber Design 6Modification of Allowable Properties for Design Use 7Example of Stress-Grade Development 81.4 The values given in parentheses are provided for infor-mation purposes only.1.5 This standard does not purport to address all of thesafety conc
7、erns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D9 Terminology Relating to Wood and Woo
8、d-Based Prod-uctsD 143 Test Methods for Small Clear Specimens of TimberD 2555 Practice for Establishing Clear Wood Strength Val-uesE 105 Practice for Probability Sampling Of MaterialsIEEE/ASTM SI-10 Practice for Use of the InternationalSystem of Units (SI) (the Modernized Metric System)3. Significan
9、ce and Use3.1 Need for Lumber Grading:3.1.1 Individual pieces of lumber, as they come from thesaw, represent a wide range in quality and appearance withrespect to freedom from knots, cross grain, shakes, and othercharacteristics. Such random pieces likewise represent a widerange in strength, utility
10、, serviceability, and value. One of theobvious requirements for the orderly marketing of lumber isthe establishment of grades that permit the procurement of anyrequired quality of lumber in any desired quantity. Maximumeconomy of material is obtained when the range of quality-determining characteris
11、tics in a grade is limited and all piecesare utilized to their full potential. Many of the grades areestablished on the basis of appearance and physical character-istics of the piece, but without regard for mechanical proper-ties. Other grades, called structural or stress grades, areestablished on t
12、he basis of features that relate to mechanicalproperties. The latter designate near-minimum strength andnear-average stiffness properties on which to base structuraldesign.3.1.2 The development of this practice is based on extensiveresearch covering tests of small clear specimens and offull-sized st
13、ructural members. Detailed studies have includedthe strength and variability of clear wood, and the effect onstrength from various factors such as density, knots (See1This practice is under the jurisdiction of ASTM Committee D07 on Wood andis the direct responsibility of Subcommittee D07.02 on Lumbe
14、r and EngineeredWood Products.Current edition approved March 1, 2006. Published March 2006. Originallyapproved in 1926. Last previous edition approved in 2002 as D 245 00 (2002)e1.2The boldface numbers in parentheses refer to references at the end of thispractice.3For referenced ASTM standards, visi
15、t 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-29
16、59, United States.Terminology D9), and other defects, seasoning, duration ofstress, and temperature.3.2 How Visual Grading is Accomplished Visual gradingis accomplished from an examination of all four faces and theends of the piece, in which the location as well as the size andnature of the knots an
17、d other features appearing on the surfacesare evaluated over the entire length. Basic principles ofstructural grading have been established that permit the evalu-ation of any piece of stress-graded lumber in terms of astrength ratio for each property being evaluated. The strengthratio of stress-grad
18、ed lumber is the hypothetical ratio of thestrength property being considered compared to that for thematerial with no strength-reducing characteristic. Thus a pieceof stress-graded lumber with a strength ratio of 75 % inbending would be expected to have 75 % of the bendingstrength of the clear piece
19、. In effect, the strength ratio systemof visual structural grading is thus designed to permit practi-cally unlimited choice in establishing grades of any desiredquality to best meet production and utilization requirements.3.3 Classification of Stress-Graded Lumber:3.3.1 The various factors affecting
20、 strength, such as knots,deviations of grain, shakes, and checks, differ in their effect,depending on the kind of loading and stress to which the pieceis subjected. Stress-graded lumber is often classified accordingto its size and use. Four classes are widely used, as follows:3.3.1.1 Dimension Lumbe
21、rPieces of rectangular crosssection, from nominal 2 to 4 in. thick and 2 or more in. wide,graded primarily for strength in bending edgewise or flatwise,but also frequently used where tensile or compressive strengthis important. Dimension lumber covers many sizes and enduses. Lumber graded for specif
22、ic end uses may dictate a specialemphasis in grading and require an identifying grade name.NOTE 1For example, in North American grading under the AmericanLumber Standards Committee, stress graded dimension lumber categoriesthat reflect end use include Light Framing, Structural Light Framing,Structur
23、al Joists and Planks, and Studs.3.3.1.2 Beams and StringersPieces of rectangular crosssection, 5 in. nominal and thicker, nominal width more than 2in. greater than nominal thickness, graded for strength inbending when loaded on the narrow face.3.3.1.3 Posts and TimbersPieces of square or nearlysquar
24、e cross section, 5 by 5 in., nominal dimensions and larger,nominal width not more than 2 in. greater than nominalthickness, graded primarily for use as posts or columns.3.3.1.4 Stress-Rated BoardsLumber less than 2 in. nomi-nal in thickness and 2 in. or wider nominal width, gradedprimarily for mecha
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