FINITE ELEMENT ANALYSIS OF COMPOSITE MULTICELL BOX GIRDER BRIDGES

Abstract

Box girders have gained wide acceptance in freeway and bridge systems due to their structural efficiency, pleasing aesthetics and economy of construction. When compared to the open section bridges, the closed box girder bridges need relatively lower material content, light weight and high bending rigidity and significantly high torsional rigidity and efficient transverse load distribution. The utilities and services can also be provided within the cells. Unfortunately, Indian designers face a daunting task as the formulation of design codes and guidelines is not even in the infancy stage. Therefore, the designers are forced to take recourse to state-of-art research and the codes of practice of European or North American countries. Therefore the present study aims to undertake some aspects of the composite box girder bridges, specifically the composite multi-cell box girders. Among the refined methods, the FEM is still the most general and comprehensive technique of analysis capturing all aspects affecting the structural response. But it is too involved and time consuming to be used for routine design purpose. Practical requirement in the design process necessitate a need for a simpler design method. This thesis work presents an extensive parametric study using the Finite element method in which twenty four, two-lane and four lane bridges of various geometries has been analysed. The parameters considered are number of cells, number of lanes, different span lengths and cross bracings. Results from published literature are used to substantiate the analytical modeling. Based on the parametric study, moment and shear distribution factors are deduced for such bridges subjected to IRC loadings as well as dead load and some design curves are given. An illustrative design example is presented.