Centrifuge Investigation of the Effects of Liquefiable Soil Interlayering and Structural Strength on the Seismic Performance of Soil-Structure Systems

Abstract

This paper discusses the results of dynamic centrifuge tests performed on 9-story model structures with different yield capacities founded on a layered liquefiable deposit with and without a silt cap. The goal was to evaluate the interacting role of soil interlayering and structure’s yield capacity on the response of soil-foundation-structure systems. The first test evaluated the seismic performance of a 9-story, steel, moment-resisting frame structure (B1) on a layered liquefiable deposit without a silt cap. The second test simulated simultaneously two models of a 9-story structure (B1 and B2) on a similar soil profile, but with a silt cap. Structure B2 was designed to have a greater yield capacity compared to B1, with other dynamic properties kept constant. The presence of a silt cap and resulting void redistribution did not notably change Structure B1’s average settlement, but it amplified residual rotations, foundation, and roof accelerations, and deformation demands on the superstructure. The stronger Structure B2 also experienced large rotations but less than B1, because of smaller flexural deflections and P-Δ moments imposed about its columns and foundation. These results point to the importance of characterizing soil interlayering as well as structure’s strength and other dynamic properties when evaluating the consequences of liquefaction.