Q1: An R.C.C. column of 30 cm diameter is reinforced with 6 bars 12 mm φ placed symmetrically along the circumference. If it carries a load of 40, 000 kg axially, the stress is

ANS:A - 49.9 kg/cm²

First, calculate the equivalent area of concrete.

Ac+(m-1)xAsc, 706.5 + (13.33-1) x 6.78 =790.
Then, 40,000/790 = 50kg/cm2. Assume M20 and 415 steel for modular ratio.

The idea of assumption for m20 answer 415 is that since the question states the RCC column of 30cm, so any mix less than M20 is not a recommendation. Same goes for the use of HYSD bars i.e. 415. Use M20 concrete.

Cal equivalent area of concrete.
= (Ac) + (m-1) * Asc.
Load ÷ equivalent area of concrete.