![]() ![]() Verticals also carry shear besides providing additional panel points for introduction of loads. In parallel chord trusses, the diagonals offer the required shear resistance. These consist of vertical and diagonal members. Their profile may however range from uniform depth to variable depth as for example in a bowstring truss. The chord members are parallel in a truss of uniform depth. They resist compressive and tensile forces. ![]() These are top and bottom members which act like the flanges of a beam. The various components of a truss bridge are the following: In order to reduce the lengths of the loaded chords (bottom chords of through trusses and top chords of deck trusses) it is convenient to make subdivided loaded chords. ![]() The angle between inclined and vertical members may be 45° to 60°. Web members of curved chord trusses are likely to be subjected to lesser forces than in the case of parallel chord trusses. If trusses whose depths vary throughout the length from both ends the forces in the chord members are more or less equalized. The trusses with parallel chords can be modified to make curved chord trusses. Accordingly the bridges are deck bridges or through bridges. Cross beams are connected to trusses either at the level of the top chord or at the level of the bottom chord. Bridges of spans 50 m to 60 m are most common. These are the most commonly used bridges and are found satisfactory for spans 10 m to as large as 300 m. (iii) Trussed Bridges or Open Web Girder Bridges: The box girder consists of steel plates fabricated to box shape and strengthened by angles and channels. ![]() These bridges are found convenient for spans up to 50 m. The trusses and girders in turn transmit all loads received by them to the abutments or supporting piers. The floor system transmits its weight and loads due to vehicular traffic to the supporting trusses or girders. The floor system provides a satisfactory surface to afford easy movement of traffic over it. Fabricated components of a steel bridge can be easily transported to the site and assembled, thus considerably reducing the construction time.Ī bridge forms mainly the super structure spanning the required length and it comprises of the floor system, the trusses or girders system, support arrangement and lateral bracing system. Steel bridges are very common for small as well as long spans in railways. Since steel possesses a high working stress compared to other materials, steel bridges work out to be economical for large spans. Arched concrete bridges have been built for still greater spans. Prestressed concrete bridges have been constructed for spans up to 60 m. Reinforced concrete bridges are found to be economical for spans exceeding 12 m. For greater spans, the dead load of masonry becomes large and hence masonry bridges work out to be uneconomical. For permanent bridges or small spans not exceeding 12 m, masonry bridges may be provided. Timber bridges are generally provided for small spans and sometimes as a temporary bridge. We also at times come across combined Highway and Railway bridges.īridges may be made of timber, masonry, reinforced concrete, prestressed concrete and steel. Based on the type of traffic for which they are provided, bridges may be classified into- (i) Highway bridges (ii) Railway bridges (iii) Foot bridges for pedestrian traffic. Introduction to Bridges:īridges are structures meant to support rail road traffic, highway traffic or pedestrian loads across openings or crossings or another set or rail or highway traffic or across any natural or artificial obstacles. In this article we will discuss about:- 1. ![]()
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