Mitigation of Seismic Accelerations by Soft Materials Embedded in the Ground

Seismic Loading And Soft Materials

Seismically-induced accelerations create many problems for structures on the ground surface. Excessive shaking can cause many types of failure, as summarised by, e.g., Wiegel (1970). Ordinarily, seismic structural design is performed by generating a surface motion for the site soil profile, using a site response code such as SHAKE (e.g. Schnabel et al., 1972), and then using this as an input motion for further seismic analysis. Soil would normally be expected to amplify the accelerations as they are transmitted from bedrock to surface, depending on its natural period (e.g. Iwasaki et al., 1978). Response spectra are commonly used to quantify the effects of soil on the response of single degree-of-freedom oscillators at the surface, for particular earthquake motions. Whether this motion is affected by interaction with the soil would not normally be considered, although recent evidence suggests that such soil-structure interaction can significantly affect structure response, either positively or negatively (Gazetas & Mylonakis, 1998; Ghosh & Madabhushi, 2005; Mylonakis & Gazetas, 2000).