BS 408:2006 pdf download – Timber structures — Structural timber and glued laminated timber — Determination of some physical and mechanical properties
5 Determination of dimensions of test pieces
The dimensions of the test piece shall be measured to an accuracy of 1 %. All measurements shall be made when the test pieces are conditioned as specified in clause 8. If the width or thickness varies within a test piece, these dimensions should be recorded as the average of three separate measurements taken at different positions on the length of each piece. The measurements shall not be taken closer than 1 50 mm to the ends. Specimens for perpendicular to grain tests shall be planed.
6 Determination of moisture content of test pieces
The moisture content of the test piece shall be determined in accordance with EN 1 31 83-1 on a section taken from the test piece. For structural timber the section shall be of full cross section, free from knots and resin pockets.
For perpendicular to grain test specimens the moisture content shall be determined from the whole specimen.
In strength tests for bending and tension parallel to grain and compression parallel to grain, the section shall be cut as close as possible to the fracture.
7 Determination of density of test pieces
The density of the whole cross section of the test piece shall be determined on a section taken from the test piece. For structural timber the section shall be of full cross section, free from knots and resin pockets. In strength tests, the section shall be cut as close as possible to the fracture. For perpendicular to grain test specimens the density of the test pieces shall be determined prior to test after conditioning from the measurements of mass and volume of the whole test piece. 8 Conditioning of test pieces The tests shall be carried out on pieces which are conditioned at the standard environment of (20 ± 2) o C and (65 ± 5) % relative humidity. A test piece is conditioned when it attains constant mass. Constant mass is considered to be attained when the results of two successive weighings, carried out at an interval of 6 h, do not differ by more than 0,1 % of the mass of the test piece.
Where the timber to be tested is not readily conditionable to the above standard environment (e.g. for hardwoodswith high densities), that fact shall be reported.
For small specimens, unless otherwise protected, test pieces shall not be removed from the conditioningenvironment more than 1 h before testing.
NOTE Test pieces can be stored in the test area for up to 24 h provided they are close piled and wrapped in vapour tightsheeting.
9 Determination of local modulus of elasticity in bending
9.1 Test piece
The test piece shall have a minimum length of 19 times the depth of the section.Where this is not possible, thespan of the beam shall be reported.
The test piece shall be symmetrically loaded in bending at two points over a span of 18 times the depth as shownin Figure 1. lf the test piece and equipment do not permit these conditions to be achieved exactly, the distancebetween the load points and the supports may be changed by an amount not greater than 1,5 times the piecedepth, and the span and test piece length may be changed by an amount not greater than three times the piecedepth, while maintaining the symmetry of the test.
The test piece shall be simply supported.
NOTE Small steel plates of length not greater than one-half of the depth of the test piece may be inserted between the pieceand the loading heads or supports to minimize local indentation.
Lateral restraint shall be provided as necessary to prevent buckling.This restraint shall permit the piece to deflectwithout significant frictional resistance.
Load shall be applied at a constant rate. The rate of movement of the loading head shall be not greater thano,003 h mm/s (see Figure 1).
The maximum load applied shall not exceed the 0,4 Fmax.BS 408 pdf download.