Effect of numerical soil-foundation-structure modeling on the seismic response of a tall bridge pier via pushover analysis

This paper examines the role of the numerical modeling of soil-foundation-structure (SFS) interaction on the seismic response of a tall, partially embedded, flared bridge pier. For this purpose, static, pushover, nonlinear, finite-element, stand-alone analyses are performed on nine different models of one of the two piers of the Mogollon Rim Viaduct, a long-span, reinforced-concrete bridge supported on pile foundations. Structural modeling considerations, such as selection of concrete constitutive models, material properties, and bond-slip and P-Δ effects, on the nonlinear response of this pier are investigated. p-y, t-z and Q-z nonlinear curves are applied to model the soil-pile interaction, and equivalent nonlinear springs are developed to reproduce the soil-pile cap interaction. In addition, the effects of the partial pier embedment and the slope of the ground surface on the lateral resistance of the pier and the total capacity of the SFS system are examined. The results illustrate how structural and geotechnical modeling approaches for the SFS interaction can affect the nonlinear response of tall bridges, and may lead to differences in the numerical prediction of local or global failure. For the case analyzed herein, the partial pier embedment and foundation flexibility can dramatically modify the structural response, and influence the bond-slip effect at the pier-pile cap connection.