Design models for steel encased high-strength precast concrete piles under axial-flexural loads

Abstract

The use of steel-encased precast concrete (SC) piles has risen rapidly for the construction of earthquake-resilient foundation systems for buildings in Japan and Southeast Asia. SC piles are used near the pile-pile cap connection owing to their increased ductility, and resistance against large bending moments and axial forces, compared to the other precast concrete piles. However, there are no official guidelines available for the design of SC piles in severe earthquakes, except for a proposed draft by the AIJ committee for the determination of bending capacities. In this work, a database of 79 tests on SC piles, all tested under axial-flexural loads, was created. The bending capacities obtained from these tests were used to verify the provisions of the proposed draft and the provisions for composite member design in AIJ, Eurocode 4 and, AISC. Furthermore, a distributed plasticity formulation was adopted to develop a non-linear static model, that takes into account the concrete confinement and local buckling of steel casing, for prediction of moment and drift capacities. The accuracy of the model was verified against various experiments, and the capability to reproduce the moment-drift relations was confirmed.