When a beam is loaded from above, which part is generally in tension?

When a beam is loaded from above, the bottom side of the beam is generally in tension. This occurs due to the bending effect caused by the downward force applied on the beam. When a load is applied on top, it causes the beam to deform, bending it downwards. As the beam bends, the top side experiences compression because the materials are pushed together, while the bottom side of the beam experiences tension as the fibers are pulled apart.

This bending behavior is governed by the mechanics of materials, where the neutral axis, which is the line within the beam where there is no longitudinal stress, is located near the center. Above this neutral axis, the material is compressed, and below it, the material is in tension. This understanding is crucial in structural engineering, as it informs the design and selection of materials capable of withstanding these stresses without failure.

In this case, the other choices do not accurately reflect the stress distribution in a beam under bending loads. The top side being in tension would be true if the beam were loaded from below, while both sides equally experiencing tension contradicts the principles of bending. The ends of the beam might have varying stress concentrations, but this does not represent the average behavior of the whole beam under load.