The design strength of a tension member due to the net section rupture for plates and threaded rods is (where An is net effective area of cross-section, fu is ultimate strength of the material and γml is partial safety factor.)
- A1·2 An fu / γml
- B0·9 An fu / γmlCorrect
- C0·6 An fu / γml
- D0·3 An fu / γml
Solution
Concept
Design strength governed by rupture (IS 800)
Formula
Tdn = 0.9 An fu / γm1
Step-by-step solution
1. IS 800:2007 clause 6.3.1: for plates, Tdn = 0.9 An fu / γm1. 2. The factor 0.9 allows for the fact that rupture is a brittle failure.
Explanation
The design strength against rupture of the critical section is 0.9 times the product of the net area and the ultimate strength divided by the partial safety factor γm1 = 1.25.
Why the other options are wrong
1.2, 0.6 and 0.3 are not the factors used by the code for plates or threaded rods.
Shortcut
Rupture: 0.9 An fu/γm1. Yielding: Ag fy/γm0.
Common mistake
Using 0.6 (the shear value in block shear).
Correct answer: B) 0·9 An fu / γml