Explain the various modes of failure encountered in prestressed concrete beams.
Explain the various modes of failure encountered in prestressed concrete beams subjected to bending moment shear and torsion. Prestressed concrete beams are high-performance structural elements, but their failure mechanisms can be complex because they involve the interaction between high-strength steel (tendons), concrete under compression, and external loading. When these beams are subjected to bending (flexure), shear, and torsion, they can fail in several distinct ways. 1. Failure due to Bending (Flexure) Flexural failure is generally categorized by how much steel is present relative to the concrete's capacity. Fracture of Steel (Under-reinforced): This is the "ideal" failure mode. The steel reaches its ultimate strength and snaps after significant deformation. This provides plenty of warning (cracking and sagging) before collapse. Concrete Crushing (Over-reinforced): If there is too much prestressing steel, the concrete in the compression zone crushes before the s...