Analysis and Design of Composite Box Girder Bridge

Abstract

Composite steel-concrete box girders are commonly used in curved bridges, interchanges, and ramps. Composite box girders are particularly strong in torsion and efficiently resist the large torsional demands created by horizontal bridge curvature and vehicle cen- trifugal forces. This work was carried out for study, the study of behavior of composite box girder bridges as per new revised codes. The analysis of the composite bridge is done by using professionally available `SAP software' for dead load, superimposed load and moving load as a class A and class 70R IRC loading. The finite element model is used to generate composite bridge superstructure model in SAP2000.Analysis and design of rectangular simply supported box girder& simply supported trapezoidal, continuous box girder & continuous trapezoidal girder bridge has been carried out . The motive behind present study is to prepare some useful interface for prelimi- nary design of composite road bridge system as per IRC:22 and IS 800:2007 provisions and then to find an economical section for the system. There are many changes in de- sign provision of 2007 code. The other aim of study is to determine the most suitable and economical section so as to achieve satisfactory performance of the structure satisfying new code provisions. Economy mainly depends on various factors like span and superstructure cross sectional dimensions . The present study includes parametric study on steel-concrete composite two lane road bridge with various alternatives consisting of variation in span and span to depth ratio and designs as per IS 800:2007. Parametric study was done for calculation of most economical L/D ratio for 15m, 20m and 25m spans as per IS 800-2007. For this all 9 alternatives costing was done with quantity analysis and rate analysis as per current market rates. From these most economical L/D ratios with minimum cost was found 13.64, 16.67 and 14.71 respectively for span 15m, 20m and 25m. Study was also done to find out the cost difference between simply supported box and trapezoidal section and also continuous box and trapezoidal section design .It is found that in simply supported rectangular box girder bridge is 4.74% economical than simply supported trapezoidal bridge while in continuous span trapezoidal open section is 0.03 % economical than continuous rectangular box span.