NON LINEAR FINITE ELEMENT ANALYSIS OF REINFORCED CONCRETE BRIDGES

Abstract

In India, reinforced bridges were designed by conventional working stress method till 2011, when IRC: 112-2011 "Code of practice for concrete road bridges" was released, thereby making it mandatory that all reinforced concrete as well as prestressed concrete bridges will be designed using the limit state philosophy of design. Also each & every bridge in india designed by the conventional working stress method in which the adequate safety can be ensured by suitably restricting the stresses in the material induced by the expected working loads (service loads) on the structure. In case of bridges these WSM approach fails to discriminate between different types of loads that act simultaneously, but have different degrees of uncertainty. Also this method does not give true idea of over loading capacity available. With the growing realization of the shortcomings of WSM in reinforced concrete design, and with increased understanding of the behaviour of reinforced concrete at ultimate loads, the limit state method is now introduced with IRC:112-2011 for concrete road bridges. These method aims for a comprehensive and rational solution to the design problem, by considering safety at ultimate loads and serviceability at working loads. As per the recent changes in design trend of bridges (i.e. limit state design), combination of loads are considered for the verification of structural strength and serviceability are considered under limit states as per IRC ;6-2010 "Standard specifications and code of practice for road bridges". The design load factors for normal case of loading for limit state of collapse as 1.35 Dead load + 1.5 Live load. And the load factors for normal case of loading for limit state of serviceability as 1.0 Dead load + 0.75 live load Generally, for the span of 12-25 m the common practice adopted in india was the reinforced concrete T-girder bridges. This study is aimed to the finding of load factors available in conventionally designed (WSM) & constructed reinforced concrete T-girder bridges of spans 18 m (Case A) & 12.2 m (Case B).