When a load is placed in the middle of a beam supported at both ends, where is the beam under the greatest stress?

When a beam is supported at both ends and a load is placed in the middle, the greatest bending stress occurs at the center, directly under the load, where the beam tends to sag the most. The bottom of the beam at the middle is in tension (stretched) while the top is in compression (squeezed). This is why beams are often deepest or reinforced in the middle of a span. The supports carry the reaction forces, but the maximum bending stress for a center load is at midspan. Understanding where a loaded beam is most stressed is part of the structural-support topic.