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Hurricane and tsunami events can generate extreme water flows in nearshore regions of the United States with catastrophic consequences to coastal structures. Field records have shown that light-frame wood structures exhibit high vulnerability to wave-induced forces due to their light construction characteristics, which feature flexible connections and slender pile foundation systems. Previous research has studied the behavior of these structures under wave action, but most studies used rigid body modeling, which is shown in this study to be insufficient for capturing the force demand on these structures. Using a fluid-structure interaction (FSI) framework, this research investigated the structural and soil flexibility effects in the interaction between elevated light-frame wood structures and water flows. Study variables included the flexibility of timber-to-timber connections, soil type, pile embedment, wavelength, and wave amplitude. The study concluded that structural and soil responses to water flows can introduce strong coupled motions. Neglecting this coupling effect may underestimate the force demand on the light-frame wood structures by more than 40%. Accounting for both structural and soil flexibilities is necessary to accurately quantify the wave force demand of these structures. [ABSTRACT FROM AUTHOR]

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]

Soil-structure interaction may play a major role in the seismic response of a bridge structure. Specifically, soil layers of low stiffness and strength may result in permanent displacement of the abutments and foundations, thus imposing important kinematic conditions to the bridge structure. A study to illustrate such phenomena is undertaken based on three-dimensional nonlinear dynamic finite-element (FE) modeling and analysis (for a specific bridge configuration under a given seismic excitation). A bridge-foundation-ground model is developed based on the structural configuration and local soil conditions of the Humboldt Bay Middle Channel Bridge. The FE model and nonlinear solution strategy are built in the open-source software platform OpenSees of the Pacific Earthquake Engineering Research Center. Based on the simulation results, the overall system seismic response behavior is examined, as well as local deformations/stresses at selected critical locations. It is shown that permanent ground deformation may induce settlement and longitudinal/transversal displacements of the abutments and deep foundations. The relatively massive approach ramps may also contribute to this simulated damage condition, which imposes large stresses on the bridge foundations, supporting piers, and superstructure. [ABSTRACT FROM AUTHOR]

A performance-based design methodology is aimed at controlling the structural damage based on precise estimations of the seismic response of the whole building–foundation system. This work presents a simplified procedure for practical damage analysis of structures considering the soil–structure interaction effects, with potential application to performance-based design of new buildings as well as to performance-based evaluation of existing buildings. A damage model based on maximum displacement and dissipated energy under monotonic loading is proposed, with the effects of cyclic load reversals being estimated by using a modified Park–Ang index. To simplify the consideration of the soil–structure interaction effects, an equivalent fixed-base oscillator with the same yield strength and energy dissipation capacity as the actual flexible-base structure is applied. Selected numerical results are presented in terms of dimensionless parameters for their general application, using a set of appropriate earthquake motions for ensuring generality of conclusions. The significance of soil–structure interaction in the structural performance is elucidated and the adequacy of the approach proposed is examined. [ABSTRACT FROM AUTHOR]