Load and resistance factor design (LRFD) approach for the reliability-based seismic design of bridge abutments

Abstract

The paper presents a study on the application of a load and resistance factor design (LRFD) approach to reliability based seismic design of bridge abutments. The failure criteria for defining the performance functions are overturning failure about the toe point, eccentricity failure of the resultant force, sliding failure along the base and bearing capacity instability. Using a pseudo-static limit equilibrium method, analysis is conducted to evaluate the stability of bridge abutments subjected to earthquake loads. The first-order reliability method (FORM) is used to estimate the probability of failure in four modes of failure. Load and resistance factors needed to maintain stability against four modes of failure by targeting various component reliability indices (2.0–4.0) are obtained for various values of coefficients of variation (COV) of unit weights of concrete and backfill (γ w and γ), friction angle of backfill and foundation soil (φ and φ b ), cohesion of foundation soil (c), vertical load acting on abutment (V) and horizontal seismic acceleration coefficient (k h ). The results have been provided in a tabular form. A comparative study between LRFD and ASD is also presented with a design example at the end.