Knots in timber are classified as a structural defect because:
Choose the correct answer
They improve the appearance of wood
They cause local grain deviation and stress concentration, reducing tensile and bending strength of the member
They increase the density of wood
They prevent insect attack
Correct Answer
B. They cause local grain deviation and stress concentration, reducing tensile and bending strength of the member
Why is this the answer?
Knots (base of branch embedded in tree stem): grain deviates around knot (cross-grain), reducing tensile strength. IS 883 limits knot sizes for structural timber. Other defects: shakes (separation along grain, from growth stresses/drying), checks (surface cracking), warping, blue stain (fungal, not structurally harmful).
Related Building Materials MCQs
More solved Building Materials questions for AE/JE Civil Engineering exams.
- The 'rebound hammer test' (Schmidt Hammer) gives an indication of:
- 'Alkali-Silica Reaction' (ASR) in concrete causes:
- Which compound in Portland cement is responsible for the early strength gain (3-7 days)...
- The compressive strength of concrete determined from a 15 cm × 15 cm cube, compared...
- A good brick when immersed in a water bath for 24 hours should not absorb more than
- The main constituent of varnish is
Practice more Civil Engineering questions
This MCQ belongs to AE Level Premium Test Series. Full tests include timed attempts, rank comparison and subject-wise analysis.