Why can prestressed concrete members span longer distances with less depth?

Prestressed concrete members can span longer distances with less depth because the process of prestressing places the concrete into a state of compression, which effectively counteracts the tensile bending stresses caused by applied loads.12

In ordinary concrete, which is strong in compression but weak in tension, structural members are susceptible to rupture under bending forces. By using pretensioning or posttensioning techniques, high-strength steel tendons are stretched and anchored to compress the concrete member. This compression ensures that no tension is experienced by the concrete until the strength of the compressed section is overcome.231

Furthermore, designers can curve the tendons within the member to exert an upward force that directly counteracts the expected downward load. By neutralizing these stretching forces, prestressed concrete allows for the creation of lighter, shallower, and more elegant structures, such as bridges and vast roofs, without requiring the heavy steel reinforcements necessary in traditional reinforced concrete designs.32