"EVALUATION OF ADEQUACY OF CDA FOR STEEL RAILWAY BIRS BRIDGE RULES",RIDGES AS PER

Abstract

Dynamic augmentation of stresses in bridge components is a complex phenomenon, depending upon various parameters of bridge, rolling stock and as well as that track geometry. Complete dynamic Analyses for bridge-vehicle system should be done to find out the exact augmentation of stresses. But it is some extent rigorous and cumbersome also. So, all the modern codes prescribe a simple multiplication factor which basically gives the fraction of live load to be taken into account for the dynamic effects. This factor is called "Coefficient of Dynamic Augment" (CDA) or Dynamic Factor In the present study moving load & dynamic analyses have been performed for two girder bridges and two truss bridges considering three categories of train loadings namely MBG and HM & 25T for three types of speeds namely operating, rated and future speeds. The moving load analyses have been performed without considering impact factor. From the stress histories, maximum bending stress value at mid-span for girder bridges and maximum combined stress value for worst tensile members for truss bridges has been found out for all the analysis cases. The damage potential of structural members have been computed using the rainflow counting algorithm and Palmgrem - Miner linear damage hypothesis .Ratios of maximum stress values and damage potential values of dynamic analysis cases to maximum stress values and damage potential values of moving load analysis (without considering CDA) cases have been found out for three types of speed namely future, rated and operational. After that Ratios of maximum stress values and damage potential values have been compared with CDA values given by IRS Bridge Rules and EN 1991-2: 2003(E).