Shear cracks are caused by diagonal tensile forces that typically occur in the web of a member near the supports.

• A. True
• B. Not Applicable
• C. False
• D. Both

Answer: (A)

When a beam carries shear, diagonal tensile stress develops in the web. Concrete has limited tensile strength, so this diagonal stress opens cracks that cut through the web at roughly 45 degrees. These cracks typically form near the supports where the shear demand is highest, and they’re oriented along the plane where the resultant tensile stress from the shear and bending is greatest. Web reinforcement, like stirrups, works to cross and hold these diagonal cracks, delaying or preventing sudden, brittle failure. That’s why this statement is true—shear cracks arise from diagonal tensile action in the web near supports.