COMPUTER AIDED DESIGN OF BRIDGE TRUSSES

Abstract

Trusses are composed of straight members connected at their ends by hinged connections to form a stable configuration .Trusses have a high strength to weight ratio and therefore are used in many structures ,from bridges ,to roof supports ,to space stations. The main load carrying members of a truss bridge are generally two trusses, which are triangulated framed structures and subjected to direct tensile or compressive forces. Truss bridges are suitable for span range of 30m to 150m.The dissertation work aims at developing a program for computer aided design of bridge trusses. Specifications laid down by the Indian Railways, the Bridge Rules, and the steel bridge code IS 1915 are used in the design of bridge trusses. The present dissertation work has been developed in C++ language. The user is allowed to select two types of trusses, i.e. Pratt truss and Warren Truss. For each truss, the user can select a number of panels in the range of 6 to 10.The user is required to enter type of truss, length of panel, depth of truss, clear spacing between channel sections etc. as the input data in the program. The output data in the program are influence line diagram, live load, dead load and impact load values, design force and designed section for the members of a truss. The program considers only dead load, live load and impact load for design of bridge trusses. The riveted type of trusses has been considered in the program. For design of upper and lower chord members, built up sections are used taking channels with plates. For design of inclined and vertical members, built up sections are used taking equal angles.