Final answer:
An arch bridge uses its curvature to distribute compression and divert weight, with keystone and voussoirs locking the structure in place. Outward thrust at the base is restrained with internal ties or external bracing, like abutments. Roman aqueducts and vaults exemplify the strength and stability provided by arches.
Step-by-step explanation:
An arch bridge uses its shape to distribute its compression and divert its weight efficiently. The curvature of the arch bridge allows forces to be resolved into compressive stresses, which eliminate tensile stresses, resulting in the weight from the top of the arch being redistributed to the sides and then down into the ground. The voussoirs and the keystone are crucial for maintaining the arch's shape and stability, as they lock the structure in place, creating a strong and stable bridge that can bear a significant amount of weight.
However, an arch's tendency to push outward at the base, known as thrust, needs to be counteracted to prevent the structure from splaying. This outward thrust can be restrained with internal ties or external bracing, such as abutments, to maintain the arch action and keep the structure intact. Roman structures, such as aqueducts, display the effectiveness of arches in distributing weight and providing structural stability, showcasing architectural innovation along with aesthetic appeal.
Arches also led to the development of other structural forms, such as vaults and domes. By placing arches side by side, or extending an arch in a linear direction, the Romans were able to create enclosed spaces with the same weight-distributing principles. The result was structures that could span large open spaces while maintaining strength and stability.