Soil Deformation and Lateral Pressure Ratcheting in Integral Bridges Absent from IRC Provisions

This study presents a comparative assessment of the structural response of integral abutment bridges, with particular emphasis on the effects of lateral earth pressure ratcheting as represented by the K* parameter in PD 6694 1:2011. A 10 m single span integral bridge was modelled using Midas civil software with realistic material properties and boundary conditions. Two analysis cases were considered: (i) a baseline model employing conventional earth pressure assumptions, and (ii) an enhanced model implementing the K* earth pressure coefficient to represent thermal cycle–induced densification of backfill behind the abutments. The results demonstrate significant differences in structural response, with the K* case exhibiting increased bending moments at the deck–abutment junction and elevated shear forces along the abutment height relative to the baseline model. These findings underscore the importance of incorporating pressure ratcheting in design calculations, particularly for the assessment of structural capacity and durability over the bridge service life. The study also identifies a gap in the Indian Roads Congress (IRC) provisions concerning lateral earth pressure development for integral bridges and proposes design considerations to better account for these effects in practice. The methodology and findings provide actionable insights for bridge engineers seeking to optimize integral abutment design for structural efficiency and long-term performance.