1. Mechanical Properties MAJOR PROPERTIES: 1.Strength 2.Stiffness Defects are not controllable in large sized pieces Full sized members are not homogenous Controllable factors: 1.Size of the specimen 2.Shape of the specimen

2. Relevant ASTM Standards ASTM D 143: Tests for small clear samples ASTM D 198: Tests for large samples ASTM D 2555: Tests establishing clear wood strength

3. Factors affecting strength Density: Directly proportional Growth: 1.Late wood: More strength 2.Early wood: Less strength Reaction wood : 1.Compression wood: in soft wood trees under side 2.Tension wood: in hard wood trees upper side Effect of moisture : Decrease in moisture below fiber saturation point increases strength and stiffness

4. Factors affecting strength Orientation: 1.Longitudinal “L” 2.Tangential “T” 3.Radial “R” Modulus of elasticity : Three moduli of elasticity E L : Elastic modulus along longitudinal direction E T : Elastic modulus along tangential direction E R : Elastic modulus along radial direction Poisson ratios : Six Poisson ratios

5. Modulus of elasticity Longitudinal direction Radial direction

6. Utilization 1.Structural timber 2.Plywood 3.Glued laminated timber 4.Manufactured wood products

7. Structural timber Roof truss Bridge truss Beams Columns 1.Posts 2.Poles 3.Piles

8. Roof truss

9. Bridge truss

11. Beams Tests as beam Bending test for Flexural strength

12. Columns Test Compression test For compressive Strength