Integral abutment bridges (IABs) provide a viable solution to address durability concerns associated with bearings and expansion joints. Yet, they present challenges in optimizing pile foundation design, particularly concerning horizontal stiffness. While previous studies have focused on the behaviour of various piles supporting IABs in non-liquefied soils under cyclic loading, research on their seismic performance in liquefied soils remains limited. This study addresses the gap by systematically comparing the performance of various pile foundations in liquefied soil, focusing on buckling mechanisms and hinge formation. Using the Pyliq1 material model and zero-length elements in OpenSees, soil liquefaction around the piles was simulated, with numerical results validated against experimental centrifuge tests. The findings indicate that IABs supported by reinforced concrete piles with a 0.8 m diameter (RCC8) experience greater displacement at the abutment top, while alternative piles, such as 0.5 m (RCC5), HP piles with weak and strong axis (HPS and HPW), steel pipes (HSST) and concrete-filled steel tubes (CFST), show pronounced rotational displacement at the abutment bottom. Maximum stress, strain and bending moments occurred at the pile tops and at the interface between liquefied and non-liquefied soil. Notably, CFST piles resisted buckling under seismic excitation, suggesting their superiority for supporting IABs in liquefied soil.

The absence of a defined allowable pile ductility in integral abutment bridges (IABs) creates a critical gap in determining the maximum safe bridge length. This paper introduces a design aid procedure to assist bridge engineers in establishing the length limits of jointless bridges. Numerical and analytical approaches were used in formulating the design aid procedure. A total of 66 finite difference models were established to obtain pile equivalent cantilever length considering various design parameters (soil stiffness, pile size, pile orientation, axial compressive load, and lateral displacement magnitude). The analytical approach incorporates a strain compatibility and equilibrium model to generate moment -curvature diagrams and load -deflection curves for standard HP sections commonly used in IABs construction. The validity of the developed design aid procedure was examined and tested with available experimental and numerical results. Lateral buckling displacement capacity of HP sections ranged from 50 to 100 mm (2 - 4 in.). Based on these displacement capacities, length limits for IABs were established and compared with existing studies. The maximum length limits for steel integral bridges fall within the range of 162 - 320 m (530 - 1050 ft), while concrete integral bridges have limits ranging from 210 to 390 m (680 - 1285 ft). These limits depend on factors such as pile size, soil stiffness, and climate conditions.