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Suspension bridges are able to span longer distances than any other type of bridge. They consist of very large vertical framing members known as anchorages which are embedded in concrete at the base. Heavy cables are attached to the top of the anchorages, then connected to the bridge deck. The cables support most of the weight of the bridge, and the roadway is suspended over the earth below.
The process of building a suspension bridge begins with constructing the anchorages. They typically require significant soil preparation, as well as large complex footings. Once the anchorages are complete and secure, the cables are connected to the top of each support using welded steel fasteners. The roadway is typically installed in sections using a crane, then fastened to the cables for support.
An arch bridge consists of a bridge deck supported by vertical framing members at each end. These framing members are known as abutments, and are connected by an arched support structure. The shape of the arch carries the load of the bridge over the entire structure, and is considered a highly efficient construction method.
The construction of these bridges generally starts with building the arch. It may be framed out of steel and poured concrete, or made from pre-cast concrete sections. The arch is supported high tension cables that are anchored to the ground during construction. Once the arch is complete, the abutments are constructed from steel, concrete or masonry, then fastened to the arch. Finally, the deck is hoisted onto the top of the arch through the use of a crane, and connected by welding or other fasteners.
A beam bridge is the simplest type of bridge construction. The bridge deck is installed over a gap or road, with the ends of the bridge resting directly on the ground on either side. In cases where the ground is unstable or unable to support the weight of the deck, the ends of the bridge are installed on vertical support members called "piers."
In most cases, the bridge deck is constructed at a separate location then transported to the job site. It is built using two steel girders connected by a steel or concrete deck. Longer spans may be built using pre-cast concrete for added strength. Once the beam bridge is complete, it is lifted into place using a crane, then secured using welding techniques or steel fasteners.