Construction Supervisor License Practice Exam

Which part of a steel beam is typically in tension?

1. The top side

2. The middle horizontal axis

3. The bottom side

4. The vertical neutral axis

The correct answer is: The bottom side

In a steel beam subjected to bending, the bottom side typically experiences tension while the top side is under compression. This behavior is a result of the way loads are applied and the resulting bending moment created in the beam. When a load is applied to the beam, it causes the beam to curve. The curvature means that the layer of material on the top of the beam is being compressed, while the material on the bottom is being stretched. This tension arises due to the distribution of internal stresses created by the bending moments, making the bottom side of a simply supported beam the zone that resists tensile forces. An understanding of how forces act on different sections of a beam is crucial in structural engineering, as it influences how beams are designed and what types of materials are used. This knowledge aids in ensuring the safety and stability of structures during their service life.