YIELD LINE ANALYSIS OF BRIDGE DECK SLABS

Abstract

The rationality and versatility are the two main rea. sons why plastic methods are gaining gradually increasing im-portance in design practice. The design procedures for concrete deck slabs which are based on elastic theory, have always been a matter of discussions, as the methods have some or the other drawbacks. The common amongst. all the defects is that .none of them _gives a true idea of factor of safety of the structure, as concrete does not remain elastic upto failure. But it is not so with the .plastic design approach, because it takes into account the behaviour of slab at collapse while designing the slab. • . An attempt has been made here to study the applicability of this design approach to the analysis of deck slabs, subjec-ted to different I.Q.C. loadings. The analysis has been carried out by yield line theory as developed by Ingerslave(6) and Johansen, which deals with reinforced concrete slabs, fail-ing in flexure, The results of the load tests conducted over deck slabs have shown. the presence of membrane action in slab before collapse, which is neglected in yield line theory app- roach. Thus the slab could sustain enhanced loads than as predicted by yield line theory. A design example solved both by Yield Line Theory and Elastic Theory in the latter part of this dissertation, shows the comparative economy of the two approaches of design. The results of the analysis show that the elastic theory is more conservative of the two; however the yield line theory is also somewhat conservative due to exclusion of membrane effects. Based on the study thus made, the adaptability of this approach , for analysis of deck slabs has been accepted at last.