Stress Distribution on Bridge Abutment due to Live Loads

S, Saranya and B, Umashankar (2013) Stress Distribution on Bridge Abutment due to Live Loads. Masters thesis, Indian Institute of Technology, Hyderabad.

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Abstract

Stress distribution on the bridge abutment plays a key role in the design of bridge abutments. Lateral stress on the abutment will be due to backfill and live loads (wheel loads). Lateral stress due to backfill can be determined by classical earth pressure theories that are well documented in the literature. However, the effect of lateral stress distribution due to live loads/wheel loads are typically assumed as an equivalent uniformly distributed load of additional height of surcharge of backfill over the surface of the backfill. IRC recommendation of 1.2m height of surcharge is based on engineering judgment and experience. This study aims to predict the lateral stress on bridge abutment more closely to the actual values. A model was developed using finite element package PLAXIS and the lateral stress distribution on abutment for various lanes are obtained. In the present study, abutment-soil system was modeled considering two cases- (a) two-layered system with a granular base layer/approach slab resting on the embankment fill material, and (b) three-layered system with an approach slab over the granular base layer resting on the embankment fill material. The equivalent height of surcharge is proposed for various moduli ratio of the pavement layers and for different lane widths (corresponding to one, two, three, four and five lanes). It is determined that the equivalent height of surcharge for case(a) two-layered system is in the range of 0.7m-1.3m and for case(b) three-layered system with an approach slab is in the range of 0.5m-0.9m.

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