Experimental investigation of the rocking response of SDOF systems on sand

Abstract

Highly inelastic foundation response is inevitable in a strong earthquake event. Shallow foundations supporting bridge piers or building columns and frame walls may experience sliding and/or uplifting from the supporting soil or bearing capacity failure. Such nonlinear foundation response does not necessarily lead to collapse of the system due to the cyclic and kinematic nature of earthquake loading. In fact, it may be beneficial for the overall system performance since high energy dissipation occurs at the foundation level, thus limiting the ductility demand exerted on the structural components. A series of centrifuge tests were performed at the CEES Centrifuge Facility in order to study the rocking response of a relatively slender single degree of freedom system on a surface foundation. The system was subjected to monotonic and slow cyclic lateral loading. The effectiveness of a shallow soil improvement that can reduce the rocking induced settlement was explored. A qualitative comparison between the centrifuge tests and equivalent reduced scale 1g tests was also performed in order to highlight the effects of the low confining stresses prevailing at 1g tests.