Question

Shrinkage deflection in case of rectangular beams and slabs can be eliminated by putting

• A. compression steel equal to tensile steel
• B. compression steel more than tensile steel
• C. compression steel less than tensile steel
• D. compression steel 25% greater than tensile steel

Answer 1

The correct option is A compression steel equal to tensile steel

The bond between concrete and steel restrains shrinkage. Therefore, the shrinkage curvature is influenced by the area of tension and compression reinforcement equally. The shrinkage curvature

${\varphi }_{sh}=\beta e_{sh}/D$

$e_{sh}\to freeshrinkage=0.003$

$D\to overalldepthofbeam$

$\beta =0.72\frac{P_t-P_c}{\sqrt{P_t}}\le 1.0$

for $0.25\le P_t-P_c\le 1$

$=0.65\frac{P_t-P_c}{\sqrt{P_t}}\le 1.0$

For $P_t-P_c\ge 1$

$P_c,P_t\to$ percentage of compression and tension steel respectively

Thus shrinkage deflection can be eliminated by making compression steel equal to tension steel.