Girder and Cantilever Bridges

A bridge is a structure carrying a roadway or a railway across rivers, valleys or other roads and railways, leaving a passage below. Bridges are classified as girder bridges, cantilever bridges, suspension bridges and also as mixed type bridges.

The plank across the stream is the simplest form of a bridge. Obviously the widest stream that can be bridged by such a method is one which is less than the length of the longest tree trunk that can be brought to the site. Such a bridge is called a girder bridge.

Modern bridge truss is derived from the tree-trunk bridge. Since the river was too wide for a single tree-trunk span the difficulty could be overcome by driving piles into the middle of the river and laying tree trunks on them.

But if the water was too deep for pile driving, other methods were available. Large brackets would be erected on each bank, jutting out over the water, and planks were laid from bracket to bracket. The deck of the bridge in the brackets had to be firmly anchored into the banks of the river, otherwise the load passed on to the overhanging part the bracket would tilt and fall into the water. This bracket construction is called a cantilever bridge.

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Single Span Beam Bridge

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Multi-Span Beam Bridge

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Дата добавления: 2015-08-27