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 section provide sufficient friction, reduce the length of the pile to save materials, and the stability is also good; the HS pile in the upper section 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.

来源平台：OCEAN ENGINEERING