STUDY OF THERMAL STRESSES IN BRIDGES USING FINITE ELEMENT METHOD

Abstract

The rise of temperature in an element of material causes the element to expand if it is unrestrained. Alternatively, if it is prevented from expanding, the rise in temperature causes an increase in stress which depends on Young's Modulus of the material. For last many years, IRC codes did not have adequate guidelines for estimation of actual stresses in a bridge, caused by the diurnal and seasonal temperature variations and the designer generally assumed that the expansion devices provided in the bridge will allow necessary movements due to thermal variations and thus relieve the possible thermal stresses. Recently, the MOST and IRC have expressed their growing concern about the magnitude and effects of so called secondary stresses due to thermal effects on concrete and pre-stressed concrete bridges and have introduced a non linear temperature distribution curve in the recent revision of IRC 6:2000. Thus in the present study, endeavors have been put in to achieve the following goals by carrying out the 3-D Analysis of a box — girder bridge having a span of 30 mts: ❖ Consequences of thermal distributions i.e. computation of stresses induced in the bridge superstructures for the design thermal gradients — Both positive and reverse gradients for the 7 proposed zones of India, using the well established methods of thermal cum structural analysis. + The results obtained from the present study have also been compared with the 2-D Analysis' and the experimental results from one of the case studies of the field. ❖ Correction factors for stresses obtained for rectangular box, have been proposed for the variations in the cross section geometry of the bridge.