Analysis and Design of Bridge Substructure and Foundation as per IRC 112:2011

Abstract

Bridge is made up of mainly two components superstructure and substructure.Many in- vestigations and research work is carried out on various type of Bridge superstructure. But the bridge substructure is not explored in greater detail. Economy of bridge depends on the cost of substructure and superstructure and therefore the bridge should be designed in such a manner that the cost of substructure and superstructure should be almost equal. For more than four decades, the design of R.C.C. Bridge is carried out by using IRC- 21 (Working Stress Method). Recently IRC has come-up with IRC 112 based on Limit State Design philosophy. In this project bridge substructure and foundation are designed using IRC 112. Structural design has been carried out considering the Ultimate Limit State (ULS) of exure, shear and torsion and Serviceability Limit State (SLS) of crack width and stress check. Substructure and foundation consist of Design of Pier cap, Pier, Pile cap and Pile. Pier cap is designed to resist loads form superstructure and to transfer the forces in pier. In general it is designed as a cantilever exural member. Pier is designed as column resisting axial force and bi axial moment and it transfer the forces to pile cap. Pile cap is design as exural member and used to transfer forces in pile from pier to pile cap. A rigid pile cap in reinforced concrete should be provided to transfer the load from the pier to the piles as uniformly as possible under normal vertical loads. Pile cap is designed using truss analogy and bending theory and comparison for both methods is carried out. Forces on pile come from pile cap, which produce axial force and bi axial moment is designed as axial compressive and bi axial bending column. Parametric study for three different type of pier i.e. Solid Rectangular type, Solid Cir- cular type and Frame type has been done for four different heights 5m, 7.5m, 10m and 15m. Seven different type of spans are considered as: 24m, 21m, 18m, 16m, 14m, 12m and 10m.Quantity estimation and cost of substructure and foundation has been derived considering above parameters and economical type of pier is derived.