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Two geotechnical centrifuge tests were designed to elicit the influence of soil-foundation-structure interaction (SFSI) and structure-soil-structure interaction (SSSI) effects on the seismic demands of an inelastic frame structure founded on individual spread footings. Four experimental cases were considered: (1) SFSI of an individual inelastic frame structure (baseline case); (2) in-plane SSSI between the frame structure and a large elastic wall structure designed to respond predominately in a rocking mode; (3) anti-plane SSSI between the frame and wall structures; and (4) combined in-plane and anti-plane SSSI between the frame structure and two wall structures. Results from Cases 1, 2, and 4 are analyzed considering 13 demand parameters. The peak seismic demands from the baseline case are compared to the peak demands from the SSSI cases to elicit the impacts of building adjacency. The number of earthquake motions that resulted in increases or decreases in the seismic demands in the frame structure are tracked for the SSSI cases. For these tests, SSSI consistently results in increased peak foundation moment and foundation base shear demands, regardless of the geometric layout of the structures. These increases propagate throughout the superstructure, resulting in increases in moment, shear and curvature ductility demands in the structural components. SSSI effects are observed to be most significant for low-to-moderate intensity earthquake motions, suggesting that particular consideration should be given to the likelihood of SSSI for highly probable earthquakes. [ABSTRACT FROM AUTHOR]

The mechanisms that control the seismic liquefaction performance of shallow foundations are identified for the special, still common case of a clay crust separating the foundation from the liquefied ground. For that purpose, foundation response is first analyzed with the nonlinear dynamic finite-difference method and consequently evaluated in connection with published field and experimental evidence. Insight is given into the excess pore-pressure buildup under the foundation, the seismic settlement accumulation, the static-bearing capacity degradation, and the inertia-induced interaction with the superstructure. It is thus shown that a naturally or artificially created nonliquefiable soil crust may effectively mitigate the detrimental effects of liquefaction and allow for a performance-based design of surface foundations, without additional improvement measures. [ABSTRACT FROM AUTHOR]

This engineering educational module on the behavior of piles in soft clays during earthquake loading sought to introduce engineering as a viable career to eighth graders and teach students how geotechnical engineers design foundations in marginal soils to minimize damage to infrastructure during earthquakes. This module could also be used at various educational levels, from elementary to middle and high school, as well as at the undergraduate level, with appropriate modifications. A 5-h module was created to simulate the real-world behavior of piles in soft clays during earthquake loading and visually show the improvement in how these same piles behave after being stabilized with a deep-soil-mixing technique. In this module, soft soil was simulated using Jell-O, piles were simulated using Slim Jims, and soil stabilization was simulated using peanut butter, marshmallows, or cheese. Each student group had to design a stabilization procedure to improve the behavior of the piles. The students competed to see who could design a stabilized pile with the least amount of deflection for the least amount of money. An abbreviated module was also administered to a group of middle-school science and mathematics teachers. The students' and teachers' learning and perceptions were assessed by administering pre- and post-assessment questions, which were matched. [ABSTRACT FROM AUTHOR]