Question

The design strength of a tension member is governed by:
A. Rupture at a critical section
B. Yielding of gross area
C. Block shear of end region
Choose the correct answer from the options given below :

• A. A and B only
• B. B only
• C. C and A only
• D. A, B and C

Hint:

Yielding is a "Serviceability" concern (too much stretching), while Rupture and Block Shear are "Collapse" concerns (total break).

Answer 1

The Correct Option is D

Concept: As per IS 800:2007 (Limit State Design), a tension member must be checked against three distinct limit states to ensure safety.

Step 1: Yielding of Gross Section (B).
The member must not undergo excessive plastic deformation over its entire length. The design strength is $T_{dg} = (A_g f_y) / \gamma_{m0}$.

Step 2: Rupture of Critical Section (A).
At the connection, the net area is reduced by bolt holes. The member fails when the stress at this net section reaches the ultimate strength. The design strength is $T_{dn} = (0.9 A_n f_u) / \gamma_{m1}$.

Step 3: Block Shear Failure (C).
This occurs at the end of the connection where a "block" of steel tears out due to a combination of shear along one plane and tension along a perpendicular plane.

Step 4: Final Strength.
The design strength of the member is the minimum of the values obtained from these three checks. Therefore, all three govern the design.