Most impacting conventional design parameters on the seismic permanent displacement of shallow foundations

Japan's previous large earthquakes have caused minimal harmful damage to shallow foundations for highway bridges. Conventional earthquake designs have ensured stability within the conventional safety standards effective against small-to mid-scale seismic forces. Although such conventional stability checks are empirically thought to provide a sufficient margin of safety for highway bridge foundations, and even against larger earthquakes, this perception has not yet been thoroughly justified. CAESAR, at PWRI, has recently developed a new macro-element capable of expressing the seismic behavior of shallow foundations with reasonable accuracy. Accordingly, this paper presents a parametric study confirming the importance of conventional design criteria and computing the differences in the seismic permanent displacement of pier-shallow foundation systems by differentiating the values of safety factors incorporated in the conventional design criteria. Within the several conventional design parameters reviewed, this study finds that checks using the pseudo-static bearing capacity may not be as important as commonly assumed.