Bridge

A bridge is a structure designed to span an obstacle, such as a river or valley, allowing vehicles, pedestrians, and other loads to pass across. Most bridges consist of a flat deck, supported by structures such as beams, arches, or cables. These structures rest on a foundation that is carefully designed to prevent the bridge from settling into the subsoil. Bridges can be constructed in a wide variety of forms, depending on their purpose and location. Notable types include viaducts, which cross wide valleys; trestles to carry heavy trains; and pontoon bridges which float on water.

The Romans and ancient Chinese built major arch bridges of stone and timber. During the Renaissance, advances in science and engineering led to wider bridge spans and more elegant designs. Concrete was perfected in the early 1800s, and proved to be superior to stone in many regards. With the Industrial Revolution came mass-produced steel, which enabled the creation of suspension and cable-stayed bridges that could span wide obstacles. Over time, the maximum achievable span of bridges has steadily increased, reaching in 2022.

The design of a bridge must satisfy many requirements, such as connecting to a transportation network, providing adequate clearances, and safely transporting its users. A bridge must be strong enough to support the weight of the bridge itself, as well as the traffic passing over the bridge. It must also tolerate violent, unpredictable stresses imposed by the environment, such as winds, floods, and earthquakes. To meet all these goals, bridge engineers use analytical methods such as limit state design and finite element method.

Many bridges are admired for their beauty, and some spectacular bridges serve as iconic landmarks that provide a sense of pride and identity for the local community. In art and literature, bridges are frequently used as metaphors to represent connection or transition. Bridges can create beneficial impacts to a community, including shorter transport times and increased gross domestic product; and also negative effects such as increased pollution and contributions to global warming. Provided by Wikipedia