DIFFERENT TYPES OF RC BRIDGES IN COMMONLY USED AND SELECTION OF TYPE OF BRIDGE, WHERE EXPERIENCE IS INVALUABLE FOR DECIDING THE TYPE OF BRIDGE.

Why so much bridges have been collapsed in Bihar during this period of the early rains , which is shown twelve number of bridges in the past seventeen days. The department of Public Works and the RDD must prepare its facts finding report in the interest of future remedial measures for which the government is too responsible to look into the matter and do needful under law code manual. Sometimes it is seen that wrong assumptions of the design &Scope are being followed by the construction agencies and instead of proposing the major bridges minor bridge structures are made which have reasonably been found incorrect and unjustified, as such type of assumptions are not correct and fruitful keeping in view the requirements of the design data prepared for the durability, rigidity, economy and ease with which pleasing appearance can be obtained suitable for the purpose and generally RC bridges in commonly used are, Solid slab bridges, simple girder bridges, continuous girder bridges, cantilever bridges rigid frame bridges both single span and multi span, Arch bridges, long trusses and bow string girder bridges. As for as use of Reinforced concrete bridges concerned these are generally used for highway bridges, their use for rail road bridges is limited. Cost is generally the governing factor for the selection of type of bridge however it too depends upon the natural conditions eg foundation and other specified requirements based on the captioned subject of design data, loading appearance, water way, time of construction, difficulties in frame work etc etc. Keeping in view the above factors required for selection of type of the bridge, it is difficult to decide upon the type of bridge at site of work for which experience is invaluable in deciding the type of bridge. For bridges having one span, simply supported deck, right angle rigid frame, right angle frame with concealed cantilever and simple supported girder with concealed cantilevers may be proposed. Simoly supported deck type is statically determinate structure and is simplest to design, however the cost of this structure is highest, when unyielding foundations are available rigid frame type is most economical. For bridges with several spans the following arrangements should be considered (1) Number of simply supported girder spans. (2) A combination of gurders provided with cantilever and short spans supported by the edge cantilevers, such a bridge is known as balance cantilever bridge (3) Continues girders (5) multi span rigid frames (5) arches. When unyielding foundations are available continues girders, multiple rigid frames and arches are best suited.