Timber as a building material
TIMBER TEST
Various test can be carryout on timber to determine its quality. Timber can be tested in the following ways:
Compressive Strength Test
The timber specimen 50*50*200 mm is used with grains generally perpendicular to the direction of the application of load. A load of 2.5 kN is initially applied to set the specimen. Deformation under compression is then measured over a central guage length of 150 mm.
The final reading at maximum load is taken. Compressive strength of good timber at 15% moisture content is 30 to 80 MPa.
TENSION TEST
The test specimen with cross section 7* 7 mm is used for this test, with the grains along the length of the specimen. The specimen is gripped in UTM and the load is applied at constant rate of 2.5 mm per minute till maximum load is applied.
The tensile strength of the specimen is the ratio of maximum load to the cross sectional area of the specimen. The tensile strength of timber parallel to the fibres is of the order of 80 to 190 MPa.
Specific Gravity Test
The timber specimen of 50*50*150 mm is taken and its weight is measured. The specific gravity of the timber is testing of timber
Where,
W = weight of the specimen, V = volume of the specimen, M = moisture content.
The specific gravity of good timber should be approximately 1.54.
Bending Test
A test specimen in the form of a beam of 50*50*100 mm is used for this test with the grains parallel to the length of the specimen. Two point loads are applied at middle third points. The load is applied at a constant rate of 3 mm per minute till crack in tension zone is seen.
The bending strength of the specimen is calculated based on simple bending equation. Bending strength of various timbers varies from 40 to 100 MPa.
Volumetric Shrinkage Test
The specimen is weighted initially and the volume is determined. The specimen is kept in an oven at 130 ± 2°C until approximately constant weight is reached. Volumetric shrinkage of the timber = (Vi-Vf) / Vi. Moisture content in percentage = (Wi-Wf)/ Wi. Oven dry specific gravity, G =( Wf/Vf ). Where V and W are initial volume and weights respectively and Vf and Wf are final volume and weights respectively.
Various test can be carryout on timber to determine its quality. Timber can be tested in the following ways:
Compressive Strength Test
The timber specimen 50*50*200 mm is used with grains generally perpendicular to the direction of the application of load. A load of 2.5 kN is initially applied to set the specimen. Deformation under compression is then measured over a central guage length of 150 mm.
The final reading at maximum load is taken. Compressive strength of good timber at 15% moisture content is 30 to 80 MPa.
TENSION TEST
The test specimen with cross section 7* 7 mm is used for this test, with the grains along the length of the specimen. The specimen is gripped in UTM and the load is applied at constant rate of 2.5 mm per minute till maximum load is applied.
The tensile strength of the specimen is the ratio of maximum load to the cross sectional area of the specimen. The tensile strength of timber parallel to the fibres is of the order of 80 to 190 MPa.
Specific Gravity Test
The timber specimen of 50*50*150 mm is taken and its weight is measured. The specific gravity of the timber is testing of timber
Where,
W = weight of the specimen, V = volume of the specimen, M = moisture content.
The specific gravity of good timber should be approximately 1.54.
Bending Test
A test specimen in the form of a beam of 50*50*100 mm is used for this test with the grains parallel to the length of the specimen. Two point loads are applied at middle third points. The load is applied at a constant rate of 3 mm per minute till crack in tension zone is seen.
The bending strength of the specimen is calculated based on simple bending equation. Bending strength of various timbers varies from 40 to 100 MPa.
Volumetric Shrinkage Test
The specimen is weighted initially and the volume is determined. The specimen is kept in an oven at 130 ± 2°C until approximately constant weight is reached. Volumetric shrinkage of the timber = (Vi-Vf) / Vi. Moisture content in percentage = (Wi-Wf)/ Wi. Oven dry specific gravity, G =( Wf/Vf ). Where V and W are initial volume and weights respectively and Vf and Wf are final volume and weights respectively.
