Soil–Structure Interaction Analysis of Transition Zone Deformations due to Imposed Abutment Displacement Cycles in an Integral Bridge

Abstract

Integral abutment bridges (IABs) are jointless bridge structures in which the bridge deck is cast monolithically with supporting piers and abutments. The absence of expansion joints and bearings eliminates maintenance costs associated with their deterioration over time. There is still a significant gap in the knowledge base surrounding the structural interaction between the bridge abutment and the backfill. The interaction of the abutment and backfill, an occurrence of soil–structure interaction, tends to cause settlements, heaving, and ratcheting of the retained soil. As a result, lateral earth pressures can increase significantly over the lifespan of the bridge. This paper provides a method of modeling IABs under the finite-element analysis (FEA) framework as a continuum model using DIANA FEA (version 10.6) structural modeling software. The presence of an approach slab was investigated and found to typically reduce settlements, while a gap developed beneath the slab due to seasonal cycles. Two clay materials were used as alternative fill materials to evaluate their effectiveness as a backfill for IABs. The stiff clay was found to behave similarly to granular soil both in terms of stress ratcheting and backfill settlement. The soft clay caused excessive backfill settlements over three times that of the stiff clay. A parametric study on the Mohr–Coulomb parameters of the hardening soil model was conducted on the slab model with granular fill. It was observed that high dilatant granular materials with low friction caused excessive heave at the far end of the backfill. Low-friction and low-dilatant materials typically behaved unfavorably, with settlements across the backfill reaching 4 mm.