In an overreinforced concrete beam, what type of failure is expected?

In an overreinforced concrete beam, the expected failure mode is characterized by a sudden failure without significant deformations prior to collapse. This happens because the beam's design features an excessive amount of steel reinforcement relative to the amount of concrete. As a result, the concrete reaches its compressive strength before the steel yields, leading to a brittle failure.

In this situation, the concrete crushes under the compressive loads, and the reinforcement does not have the opportunity to yield and contribute to a ductile failure mode. This contrasts with properly designed beams, where yielding of the steel reinforcement allows for deformation and energy dissipation before collapse, providing warning signs of impending failure. Overreinforced beams do not exhibit this behavior; instead, they fail suddenly and can lead to catastrophic results with little to no advance warning, making them particularly dangerous in structural applications.