BS/EN 302-4-2013 pdf download.Adhesives for load-bearing timber structures Test methods
Part 4: Determination of the effects of wood shrinkage on the shear strength.
b) for assessing the suitability and quality of adhesives for load-bearing timber structures:
c) for determining if the adhesive is capable of withstanding stresses due to wood shrinkage without unacceptable loss of strength.
This test s intended primarily to obtain performance data for the classification of adhesives for load-bearing timber structures according to their suitability for use in defined climatic environments. This test is carried out on Norway spruce (Picea abies L.).
This method is not intended for use to provide numerical design data and does not necessarily represent the performance of the bonded member in service.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies.
EN 301, Adhesives, phenolic and aminoplastic. for load-bearing timber structures — Classification and performance requirements
EN 13183-1, Moisture content ole piece of sawn timber — Part 1: Determination by oven dry method
ISO 5893, Rubber and plastics test equipment — Tensile. Ilexural and compression types (constant rate of traverse) — Specification
ISO 6344-2, Coated atxasives — Grain size analysis — Part 2: Determination of grain size distribution of macrogrits P12 to P220
3 Principle
A crosswise double joint with 0,5 mm thick glue line is submitted to a dry storage treatment and then strained to failure by a compressive shear force.
4 Apparatus
4.1 TestIng machIne, which shall be either:
a) capable of maintaining a constant rate of loading of (20 ± 5) kNlmin; or
b) capable of maintaining a constant crosshead speed as described in ISO 5893.
5 Method
5.1 General
5.1.1 Selection of timber
Use Norway spruce (Picea abies L) having a density of (450 ± 25) kg/rn3 measured at 12 % moisture content
as determined by oven drying (according to EN 13183.1).
5.1.2 PreparatIon of cover pieces
From three boards with a length of at least 1 200 mm. prepare three pairs of solid Norway spruce cover pieces that are knot-free, straight grained with growth rings that are approximately tangential to the face and have a radius of 60 mm to 140 mm. The cover pieces shall be
a) 400 mm in length,
b) 140mm in width, and
C) (20 ± 0,5) mm in thickness
after conditioning, measurement of moisture content (oven dry method according to EN 13183-1) and final
preparation. Each matching pair of cover pieces is intended for the production of a specimen.
5.1.3 Preparation of core pieces
Prepare three laminated spruce core pieces that are knot-free. straight-grained and with annual rings at an angle of 350 to 55° relative to the surface (see Figure 1). The dimensions of the core pieces shall be
a) 400 mm in length,
b) 140mm in width, and
c) (40,0 ± 0,5) mm in thickness
after conditioning, measurement of moisture content (oven dry method according to EN 13183-1) and final preparation.
These laminated core pieces shall be produced of two boards with a width of (75 ± 2) mm. and a thickness of at least 48 mm. The two boards shall be bonded together longitudinally with a phenol-resorcinol-formaldehyde adhesive which passed EN 301 (used according to the adhesive manufacturers instructions), with an annual ring orientation as indicated in Figure 1.
5.1.4 Conditioning
Condition the core and cover pieces such that the average moisture content of all three pieces used in an assembly is (17,5 ± 0,5) %. Individual core and cover pieces may have a moisture content of (17 ± 1) %, as determined by the oven-dry method. according to EN 131 83-1.
NOTE Storage at (20 ±2) DC and 75 % to 80 % relative humidity would be expected to give rise to a moisture content In the wood of between 16% and 18%.
Not more than 8 h before bonding, either lightly plane or lightly sand, using a grade P100 abrasive paper as defined in ISO 6344-2, each surface to be bonded. Remove any dust carefully.
Do not touch or soil the prepared surface.
5.2 Preparation of the bonded assemblies
Before bonding the specimens together. take a sample from each of the core and cover pieces for the wood moisture content determination, using the oven-dry method, according to EN 13 183-1.
Calculate and record each specimen’s mean moisture content using the following formula:BS/EN 302-4-2013 pdf download.