Objective Question & Answer

Let, 'x' be the depth of actual neutral axis x_u' be the depth of critical neutral axis,

Then,

If x > x_u' the concrete attains its maximum stress earlier which means that tension steel does not yield upto ultimate

strength and the section will be over reinforced which results in compressive failure, brittle failure, primary compression

failure.

If x < x_u the steel in the tensile zone attains its maximum stress earlier which means that tension steel yields upto

ultimate strength and the section will be under reinforced which results in tensile failure (ductile failure) secondary

compression failure.

If x = X_u , the concrete and steel attain their maximum stresses simultaneously which means that simultaneous

attainment of limiting compressive strain of 0.0035 in concrete and the minimum specified tensile strain to ensure

yielding of steel and the section will be balanced section.

Note:

Failure always occurs due to crushing of concrete on compression face.

Under reinforced concrete flexural members are deeper and undergo larger deflection than balanced and over

reinforced member.

Over-reinforced and balanced concrete flexural member are stiffer than under reinforced member.