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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
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This standard was proposed by and is under the jurisdiction of SAC/TC 41/SC 4 Subcommittee on Structural Timber of National Technical Committee on Timber of Standardization Administration of China.
Standard for establishing characteristic values for mechanical properties of structural-use oriented strand board
1 Scope
This standard specifies the method for determining the characteristic values of mechanical properties of the structural-use oriented strand board, including the sampling, test methods and characteristic values determination of oriented strand board.
The methods specified in this standard are applicable to structural-use oriented strand board with timber as raw materials.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 17657 Test methods of evaluating the properties of wood-based panels and surface decorated wood-based panels
GB/T 18259 Terms of wood-based panel and its surface decoration
GB/T 31264-2014 Test methods for mechanical properties of structural wood-based panels
LY/T 1580 Oriented strand board
LY/T 2059 Steel nails for timber structures
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purpose of this document, the terms and definitions specified in GB/T 18259 and LY/T 1580 as well as the following ones apply.
3.1.1
structural-use oriented strand board (OSB)
oriented strand board serving as the basic member of buildings or other structures and used under bearing conditions
3.1.2
characteristic values of mechanical properties
statistical value obtained through calculation with test data, which is used to judge the properties of the structural-use OSB or to determine the design values and which, in this standard, is the fractile of 5% or average value on the basis of assuming that the confidence coefficient is 75% for the statistical distribution of corresponding mechanical property indexes
3.1.3
major axis; primary axis
direction of board parallel to the oriented forming direction of the stand board on surface, which has much better mechanical property than the minor axis and which, for the oriented strand board with the size of 1,220 mm×2,440 mm, generally refers to the 2,440 mm direction, i.e., the length direction of the board
3.1.4
minor axis; secondary axis
direction of board perpendicular to the oriented forming direction of the stand board on surface, which has relatively lower mechanical property than the major axis and which, for the oriented strand board with the size of 1,220 mm×2,440 mm, generally refers to the 1,220 mm direction, i.e., the width direction of the board
3.1.5
planar shear
applying or forming shear force within two planes parallel to the board surface to cause shear deformation of the plate along its plane, as shown in Figure 1
3.1.6
through-the-thickness shear
applying or forming shear force on two side edges of the board that is parallel to the major axis or minor axis of the OSB to cause the board to be sheared on the whole thickness and to deform due to shear in the direction parallel to the shear force, as shown in Figure 2
3.1.7
dowel-bearing performance
performance of OSB to withstand the pressure of metal connecting pieces of dowels (round nails, wood screws, bolts, etc.) and pressure-bearing performance measured by applying pressure parallel to the major axis or minor axis of OSB to dowel connecting pieces horizontally placed on the board edge
3.1.8
nail-head pull-through resistance
force required for nail-head to penetrate OSB, which is used to indicate the board's capability in resisting being penetrated by the connector end
3.1.9
equivalent specific gravity
specific gravity of solid wood sawn timber with the same nail-holding ability or dowel-bearing performance as OSB, which is determined by measuring the connection performance of OSB and used to represent the equivalence of connection performance between OSB and solid wood sawn timber
3.2 Symbols
For the purposes of this document, the following symbols apply.
A——the cross sectional area, mm2;
b——the width of test piece, mm;
D——the diameter of connecting piece, mm;
Eb——the bending-resisting elasticity modulus, MPa;
EbI——the bending rigidity, N·mm2;
Ec——the axial compressive modulus of elasticity, MPa;
ECA——the axial compressive stiffness, N;
Et——the axial tensile modulus of elasticity, MPa;
EtA——the axial tensile stiffness, N;
f——the characteristic values of mechanical properties;
——the average value of mechanical properties;
fb——the bending strength, MPa;
fbW——the flexural capacity, N·mm;
fc——the axial compressive strength, MPa;
fcA——the axial compressive bearing capacity, N;
fcp——the compressive strength of board surface, MPa;
fe——the dowel-bearing strength, MPa;
ft——the axial tensile strength, MPa;
ftA——the axial tensile capacity, N;
fv——the through-the-thickness shear strength, MPa;
fvt——the through-the-thickness shear capacity, N/mm;
fs——the planar shear strength, MPa;
fs(Ib/S)——the planar shear capacity, N;
Gv——the through-the-thickness shear modulus, MPa;
Gvt——the through-the-thickness shear stiffness, N/mm;
I——the inertia moment of section, mm4;
Ib/S——the shear constant of section, mm2;
k——the characteristic value coefficient;
s——the standard deviation;
S——the clear distance of section, mm3;
t——the board thickness, mm;
W——the section modulus, mm3.
ρeq——the equivalent specific gravity.
4 Sampling and test piece preparation
4.1 The sample board shall be randomly selected from products of the same type, grade and thickness, and the sample formed by the sample boards shall be representative.
4.2 The minimum number of samples for bending performance test is 60, and that for other mechanical property tests is 30.
4.3 Each test piece used in each performance test shall be taken from different sample boards in the same sample. For the sampling positions of different test pieces in the sample board, please refer to GB/T 31264-2014, Annex A.
4.4 The moisture content of the test pieces shall be adjusted according to the provisions of GB/T 31264-2014, 5.1.
5 Test methods
5.1 Moisture content and air-dry density
The test shall be conducted in accordance with those specified in LY/T 1580. Measurement of moisture content and air-dry density shall be carried out during various mechanical property tests, for which at least one test piece shall be taken from each sample board.
5.2 Bending performance
The bending performance of the board in the major axis and minor axis directions shall be determined according to the provisions specified in GB/T 31264-2014, 6.1 "pure bending performance for flat bending". The bending rigidity and flexural capacity shall be determined with a same test piece at the same time, dividing the result by the test piece width and expressed by bending rigidity per millimeter in width (EbI) (N·mm2/mm) and by flexural capacity per millimeter in width (fbW) (N·mm/mm).
5.3 Planar shear resistance
The planar shear resistance of the board in the major axis and minor axis directions shall be determined in accordance with the provisions specified in GB/T 31264-2014, 10.1 or 10.2 (see Figure 1), dividing the result by the width of the test piece and expressed by planar shear capacity per millimeter in width [fs(Ib/S)] (N/mm).
Figure 1 Schematic diagram for planar shear resistance test
5.4 Through-the-thickness shear resistance
The shear resistance test of the board in the major axis and minor axis directions shall be carried out in accordance with the provisions specified in GB/T 31264-2014, 9.1 or 9.2 (see Figure 2), and the shear performance shall be determined in accordance with the provisions specified in GB/T 31264-2014, 9.3, with the result expressed by shear capacity per millimeter in length (fvt) (N/mm) and shear stiffness per millimeter in length (Gvt) (N/mm).
Foreword i
1 Scope
2 Normative references
3 Terms, definitions and symbols
3.1 Terms and definitions
3.2 Symbols
4 Sampling and test piece preparation
5 Test methods
5.1 Moisture content and air-dry density
5.2 Bending performance
5.3 Planar shear resistance
5.4 Through-the-thickness shear resistance
5.5 Axial tension property
5.6 Axial compressive property
5.7 Nail-holding ability
5.8 Dowel-bearing strength
5.9 Nail-head pull-through resistance
5.10 Board surface compressive strength
6 Determination of characteristic values
Annex A (Informative) Determination of equivalent specific gravity value of connection performance of OSB
Annex B (Normative) Characteristic value coefficient and sequence
