Ingeniero

Bridging Communities and Towns!

Beam and Truss Bridges
Beam bridges are the simplest and least expensive type of bridge to build. The most simple beam bridges consist of a horizontal beam that issupported on each end by columns or piers. The weight of the beam and any additional load on the bridge is transferred directly to the piers. However, the beam itself must be able to support its ownweight and loads between the piers. When a load pushes down on the beam, the top portion of the beam is pushed together by a compressive force while a tensile force stretches the lower portion. Thefarther apart the supports or piers, the weaker a beam bridge becomes. For larger beam bridges designed for heavy car and railroad traffic, the beams are substituted by simple trusses, or triangularunits, which are more economical than solid beams. Engineers have used many different truss patterns in bridges. Therefore, most beam bridges rarely span more than 200 feet (61m), however, old trussbridges crossing major rivers are often as long as 500-600 feet (152-183m), not including end supports such as piers.

Arch Bridges
Arch bridges are the easiest type of bridge to recognize. They areone of the oldest types of bridges and have extraordinary natural strength. Instead of pushing straight down as beam bridges do, the weight of the arch bridge and any additional load on the bridge iscarried outward along the curve of the arch to the supports at each end. These supports are called abutments. Abutments distribute the load from the bridge and keep the ends of the bridge from spreadingout. The Romans were masters of the arch bridge. Many of their arch bridges used little or no mortar, or "glue," to hold the stones together. The goal of an arch bridge is to carry all loads incompression, without any tensile loads present. The stones in the structures stay together by the sheer force of their own weight and the compression transferred between them. The size of the arch, or...