Influence of Relative Stiffness on Integral Bridge Design

Integral bridges are a low-maintenance form of bridge construction used worldwide. Their jointless structure eliminates bearing and expansion joint replacement bringing a reduction in lifecycle cost, carbon emissions, and socio-economic impact from road and rail disruption, therefore offering a resilient infrastructure solution in the face of a changing climate. By better understanding earth pressure ratcheting in the backfill due to repeated thermal movements of the deck, integral bridge use can increase to greater spans and skews while excessive design conservatism can be reduced. This paper explores the integral bridge problem and design code prescriptions before using analytical, numerical, and centrifuge modeling to show that soil-structure interaction, especially the relative stiffness of soil and structure, can reduce abutment bending moments by 30% and that this is largely unaccounted for in the current U.K. design code PD 6694–1. Preliminary results showed a similar influence of stiffness on seismic response.