Flexural collapse in overreinforced beams is a primary compression failure.

Flexural collapse refers to the failure of a beam due to excessive bending. It occurs when the applied loads cause the beam to exceed its maximum bending capacity, resulting in a loss of structural integrity. In overreinforced beams, the steel reinforcement is designed to carry more tension than required, leading to a beam that is stronger in tension than in compression.

Primary Compression Failure:
When a beam fails in flexure, it typically fails in compression on the top surface of the beam. This is known as primary compression failure. In overreinforced beams, the excessive reinforcement prevents the concrete from reaching its full compressive strength before failure occurs. As a result, the failure in these beams is primarily due to compression.

Causes of Primary Compression Failure in Overreinforced Beams:
1. Excessive Reinforcement: The overreinforced beams have a higher amount of steel reinforcement than required by design. This excessive reinforcement restricts the ability of the concrete to undergo significant compressive deformation before failure.
2. Brittle Behavior of Concrete: Concrete is inherently weak in tension and exhibits brittle behavior. In overreinforced beams, the concrete does not experience significant tensile stresses, leading to a lack of ductility and reduced energy absorption capacity. This makes the beam more vulnerable to compression failure.
3. Inadequate Concrete Cover: Overreinforced beams often have a smaller concrete cover due to the larger steel reinforcement. This reduced cover reduces the ability of the concrete to withstand compressive stresses, further contributing to primary compression failure.

Consequences of Primary Compression Failure:
When a beam fails in primary compression, it typically results in sudden and catastrophic failure. The failure may occur without warning, leading to a complete collapse of the structure. This can pose a significant risk to the safety of occupants and can result in extensive damage to the surrounding area.

Conclusion:
Flexural collapse in overreinforced beams is primarily a compression failure. The excessive reinforcement prevents the concrete from reaching its full compressive strength, leading to the failure of the beam under compression. Understanding the causes and consequences of primary compression failure is crucial for the safe design and construction of beams to prevent structural failures.