Professor Jonathan Stewart, Chair of the Civil & Environmental Engineering Department, will present collaborative work with Scott J. Brandenberg, George Mylonakis, and he on “Kinematic Framework for Evaluating Seismic Earth Pressures on Retaining Walls” at the ASCE Los Angeles Geo-Institute dinner meeting. September 23 2015, 5:30 pm, Stevens Steak House. Reservations to .
Professor Stewart’s technical expertise is in geotechnical earthquake engineering and engineering seismology, with emphases on seismic soil-structure interaction, engineering characterization of earthquake ground motions, seismic performance of levees and other embankments, and seismic ground failure
During earthquake ground shaking earth pressures on retaining structures can cyclically increase and decrease as a result of inertial forces applied to the walls and kinematic interactions between the stiff wall elements and surrounding soil. The application, based on limit equilibrium analysis, of a pseudostatic inertial force to a soil wedge behind the wall [the mechanism behind the widely-used Mononobe–Okabe (M–O) method] is a poor analogy for either inertial or kinematic wall–soil interaction. This paper demonstrates that the kinematic component of interaction varies strongly with the ratio of wavelength to wall height (λ/H), asymptotically approaching zero for large λ/H, and oscillating between the peak value and zero for λ/H<2.3. Base compliance, represented in the form of translational and rotational stiffness, reduces seismic earth pressure by permitting the walls to conform more closely to the free-field soil displacement profile. This framework can explain both relatively low seismic pressures relative to M–O predictions observed in recent experiments with λ/H>∼10, and relatively high seismic earth pressures relative to M–O from numerical analyses in the literature with λ/H=4.