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.

Integral abutment bridges (IAB) have become increasingly popular in the past few decades due to their design simplicity. UK design rules limit the length of IABs to 60 m, due to the issues associated with thermal strains, settlement, and pressure build-up behind the abutment. A cyclic loading test, representing seasonal thermal fluctuations, was conducted on a 1/12 scaled-down retaining wall of a conventional full-height IAB. The test was then repeated with the inclusion of displacement compensation units (DCU) in the form of conical disc springs (CDS) and hollow rubber cylinders (HRC), which operate in a pre-deformed shape. The results show some remarkable improvements in the IAB performance with DCUs. The soil backfill pressure was reduced to 30% and 47% with CDSs and HRCs, respectively. Furthermore, no settlement was observed, as compared to the conventional IAB test which recorded a 20 mm settlement after 100 cycles. Non-linearity in the force-deflection behaviour of DCUs enables expansion and contraction of the deck to be accommodated with minimal fluctuation of backfill pressure. Finally, a finite element (FE) model of an HRC applied with two temperatures has been analysed and compared with the IAB wall test, which suggests that both analyses showed some correlation.

Integral abutment bridges (IABs) have been widely applied in bridge engineering because of their excellent seismic performance, long service life, and low maintenance cost. The superstructure and substructure of an IAB are integrally connected to reduce the possibility of collapse or girders falling during an earthquake. The soil behind the abutment can provide a damping effect to reduce the deformation of the structure under a seismic load. Girders have not been considered in some of the existing published experimental tests on integral abutment-reinforced-concrete (RC) pile (IAP)-soil systems, which may not accurately represent real conditions. A pseudo-static low-cycle test on a girder-integral abutment-RC pile (GIAP)-soil system was conducted for an IAB in China. The experiment's results for the GIAP specimen were compared with those of the IAP specimen, including the failure mode, hysteretic curve, energy dissipation capacity, skeleton curve, stiffness degradation, and displacement ductility. The test results indicate that the failure modes of both specimens were different. For the IAP specimen, the pile cracked at a displacement of +2 mm, while the abutment did not crack during the test. For the GIAP specimen, the pile cracked at a displacement of -8 mm, and the abutment cracked at a displacement of 50 mm. The failure mode of the specimen changed from severe damage to the pile top under a small displacement to damage to both the abutment and pile top under a large displacement. Compared with the IAP specimen, the initial stiffness under positive horizontal displacement (39.2%), residual force accumulation (22.6%), residual deformation (12.6%), range of the elastoplastic stage in the skeleton curve, and stiffness degradation of the GIAP specimen were smaller; however, the initial stiffness under negative horizontal displacement (112.6%), displacement ductility coefficient (67.2%), average equivalent viscous damping ratio (30.8%), yield load (20.4%), ultimate load (7.8%), and range of the elastic stage in the skeleton curve of the GIAP specimen were larger. In summary, the seismic performance of the GIAP-soil system was better than that of the IAP-soil system. Therefore, to accurately reflect the seismic performance of GIAP-soil systems in IABs, it is suggested to consider the influence of the girder.

Given the horizontal low cycle reciprocating motion of the integral abutment bridge pile foundation under cyclic loading of temperature, the traditional reinforced concrete (RC) pile cannot be applied to accommodate the large longitudinal deformation appropriately because of its significant lateral stiffness and its weak cracking resistance; the surface area of the H-shaped steel (HS) pile is small, it cannot provide enough friction in deep soft soil areas, and due to its high cost and easy buckling during pile driving, it is not suitable for domestic popularization. This paper proposes a new concept of composite stepped pile consisting of HS and rectangular RC piles, the RC pile in the lower provide sufficient friction, reduce the length of the pile to save materials, and the stability is also good; the HS pile in the upper has good horizontal compliance, which can meet the horizontal deformation requirements of the integral abutment bridge. Pseudo-static tests of model piles were carried out of one HS pile and two HS-RC stepped piles with different stiffness ratios of 0.25 and 0.5. The test results show that the cracking displacements of HS-RC (0.25) and HS-RC (0.5) stepped piles are 10 similar to 15 mm and 5-8 mm, respectively, and the corresponding cracking loads are 4.66-5.99 kN and 3.22-4.52 kN, indicating the stepped pile with a smaller stiffness ratio has a stronger crack resistance; The HS-RC stepped pile has larger plastic deformation capacity, and its initial stiffness of pile-soil system is smaller, 0.48 times and 0.57 times that of RC piles, respectively, and can be applied to integral abutment bridges. Based on these tests, a finite element (FE) model using OpenSees software was validated and used for a detailed numerical simulation analysis considering the pile-soil interaction of HS-RC stepped piles. Simulating the low-cycle reciprocating motion of full-scale stepped piles under the control of displacement loads, the effects of stiffness and length ratios on the load-bearing performance of stepped piles were studied and analyzed. The FE simulation found that the stepped pile's crack resistance can be improved by reducing the stiffness of the HS pile's upper section. Still, the stepped pile's horizontal load-bearing capacity (deformation) is very low if the stiffness is unreasonably small. Furthermore, increasing the upper HS pile length cannot significantly change the horizontal load-bearing capacity of the stepped pile because the deeper pile below the inflection point will not significantly take part in the bending deformation. According to the simulation, the theoretical optimum ratio is 0.33. With the practical construction and soil property variance, it is recommended that the length ratio of the stepped pile be around 0.33 to 0.5.

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.

Integral abutment bridges (IABs) are a family of jointless bridges that have gained popularity owing to their simplified designs and sustainable construction practices. IABs are small- and medium-span bridges that do not have expansion joints or bearings, thereby reducing the cost of maintenance. The span of IABs is primarily dependent on the magnitude of the thermal stresses considered during the design process. However, the adoption of IABs has been limited globally because of the inherent complexity of the design caused by the large number of indeterminacies originating from rigid connections and soil-spile interactions. This has led to variations in the design of IABs among transportation agencies worldwide. This literature review aims to highlight the variations in major IAB projects constructed worldwide. Additionally, the bibliographic analysis performed for IABs identified key topics studied by researchers, which are discussed in detail in the current state-ofthe-art. The objective of this literature survey is to provide practical bridge designers and researchers with an understanding of previous and ongoing developments in IABs.