Question

In the design of a base plate, the bearing strength of concrete as per the Indian Standard (IS) 800 : 2007, is taken as (f_ck is characteristic strength of concrete)
1. 0.4 f_ck
2. 0.45 fck
3. 0.5 fck
4. 0.60 fck

Answer 1

Correct Answer - Option 2 : 0.45 fck

Explanation:

(i) Column bases should have sufficient stiffness and strength to transmit axial force, bending moments and shear forces at the base of the columns to their foundation without exceeding the load carrying capacity of the supports. Anchor bolts and shear keys should be provided wherever necessary, Shear resistance at the proper contact surface between steel base and concrete/grout may be calculated using a friction coefficient of 0.45.

(ii) The nominal bearing pressure between the base plate and the support below may be determined on the basis of linearly varying distribution of pressure. The maximum bearing pressure should not exceed the bearing strength equal to 0.6f_ck, where f_ck is the smaller of characteristic cube strength of concrete or bedding material.

(iii) For design of base plate, we will take the value of bearing pressure = 0.45 f_ck (As per IS 456, we take design strength of concrete as 0.45 f_ck).