Influence of loading path on cyclic mechanical response of small-scale shallow strip footing on loose sand

Abstract

This paper aims at experimentally exploring the behaviour of a small-scale 1g shallow strip footing on loose dry sand, subjected to vertical and horizontal cyclic loads. An experimental apparatus has been developed and calibrated, and some series of monotonic and cyclic tests with different combinations of load direction and cycle amplitudes have been carried out. Results are presented and discussed in terms of evolution of foundation global stiffness, damping properties, and settlement accumulation along both vertical and horizontal directions with increase in the load cycle’s number. The coupling effect between vertical and horizontal loads is highlighted, underlying its important role even at a low number of cycles, when, in the design practice, the behaviour of the system is often considered to be linear elastic and path independent. The observation also allowed the inference that a variation of the inclination of the cyclic loads may induce significant differences (up to one order of magnitude) in the global stiffness and damping properties. Far from having exhaustively investigated the subject and from the aim of proposing a new empirical quantitative relationship to be directly employed in the design practice, this paper was primarily focused on highlighting some aspects of the mechanical behaviour of the system that are still rather unknown. A further in-depth study allowed the analysis of experimental results within the framework of a meaningful physical interpretation, showing the results to be particularly useful in the perspective of a displacement-based design approach, as required by the current design standards.