In a beam with a positive bending moment, where does the maximum tensile stress occur?

In a beam subjected to a positive bending moment, the maximum tensile stress occurs at the bottom of the beam. This is due to the way bending moments influence the internal stress distribution within the beam.

When a beam is subjected to bending, the material experiences compressive stress on one side (the top, in this case) and tensile stress on the opposite side (the bottom). A positive bending moment typically indicates that the beam is sagging, meaning the top fibers are being compressed and the bottom fibers are being stretched. As the bending moment increases, the tensile stress at the bottom becomes more pronounced, reaching its maximum at the point of maximum moment, commonly found at the midspan of simply supported beams or near the center of beams with certain types of loading.

It’s essential to understand that while the bottom of the beam is where the tensile stress is maximum, the actual location of this stress can vary depending on the specific loading and support conditions. However, for a general analysis of positive bending moments in typical beam configurations, the bottom of the beam will consistently experience the greatest tensile stress.