This video shows how a reinforced concrete beam fails when too much longitudinal (or flexural) reinforcement is provided.
Longitudinal steel bars are provided to resist the tensile forces in the bottom of the beam due to bending (or flexure).
Shear reinforcement (links) have also been provided to ensure that the beam doesn’t experience a shear failure.
Note how the concrete starts to fail in compression, at the top of the beam, close to mid-span, where the bending moment is highest.
Although the graph shows that the beam is able to support an applied load of almost 20kN, note the sudden loss of strength once the compression resistance of the concrete is exceeded.
This sudden, brittle mode of failure is unsafe because there is little warning that the beam is about to fail.
Hence, reinforced concrete designers always try to ensure that beams are designed as under-reinforced and not over-reinforced.
This video will help students answer questions such as:
- What is reinforced concrete?
- How does a simply-supported, reinforced concrete beam deflect under a downwards load?
- Where does the reinforcement need to be positioned in a simply-supported beam to resist tension forces due to bending?
- What is the failure mechanism for an over-reinforced concrete beam?
Bending Failure of an Over-Reinforced Concrete Beam by Think Up is licensed under a Creative Commons Attribution 3.0 Unported License.
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