Question

Vertical prestressing is done to reduce

• A. Frictional losses
• B. Creep losses
• C. Principal tensile stress
• D. Anchorage slip loss

Hint:

Horizontal prestressing mainly resists bending, whereas vertical prestressing is primarily provided to reduce principal tensile stress caused by shear.

Answer 1

The Correct Option is C

Concept: Prestressing introduces compressive stresses into concrete before external loads are applied. Vertical prestressing is mainly provided to counteract tensile stresses produced due to shear forces. It helps reduce the principal tensile stress, thereby preventing diagonal cracking in concrete members.

Step 1: Purpose of vertical prestressing. Vertical prestressing develops compressive stresses in the vertical direction. These compressive stresses oppose the tensile stresses caused by shear.

Step 2: Effect on the member. As the compressive stresses increase, \[ \boxed{\text{Principal tensile stress decreases}.} \] This improves the shear resistance and minimizes the formation of diagonal cracks. Hence, \[ \boxed{\text{Vertical prestressing is used to reduce principal tensile stress}.} \] Therefore, the correct option is \[ \boxed{(C)\;\text{Principal tensile stress}.} \]