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During a tsunami or storm surge event, coastal infrastructure and ports are subject to a series of disparate physical hazards that can cause significant damage and loss of life. Among these, debris impact loading during inundation events is chaotic, complex, and thus far minimally understood, especially when considering the accumulation of individual debris into a large debris field. This work provides the results of a comprehensive experimental study of the impact and subsequent damming of chaotic debris fields, including more than 400 individual trials; this scope of this paper describes the experimental design and initial analysis of wave-driven debris-induced loading for select configurations. These data include both the impact phenomena and subsequent damming by debris accumulation and find strong correlation between increasing debris field density and high impact forces. High frequency impact forces and low frequency damming signals are considered via fast Fourier transform methods. Overall trends in wave-induced debris forcing from large debris fields are presented.

Studies of recorded ground motions and simulations have shown that deep sedimentary basins can greatly increase the damage expected during earthquakes. Unlike past earthquake design provisions, future ones are likely to consider basin effects, but the consequences of accounting for these effects are uncertain. This article quantifies the impacts of basin amplification on the collapse risk of 4- to 24-story reinforced concrete wall building archetypes in the uncoupled direction. These buildings were designed for the seismic hazard level in Seattle according to the ASCE 7-16 design provisions, which neglect basin effects. For ground motion map frameworks that do consider basin effects (2018 USGS National Seismic Hazard Model), the average collapse risk for these structures would be 2.1% in 50 years, which exceeds the target value of 1%. It is shown that this 1% target could be achieved by: (1) increasing the design forces by 25%, (2) decreasing the drift limits from 2.0% to 1.25%, or (3) increasing the median drift capacity of the gravity systems to exceed 9%. The implications for these design changes are quantified in terms of the cross-sectional area of the walls, longitudinal reinforcement, and usable floor space. It is also shown that the collapse risk increases tomore »2.8% when the results of physics-based ground motion simulations are used for the large-magnitude Cascadia subduction interface earthquake contribution to the hazard. In this case, it is necessary to combine large changes in the drift capacities, design forces, and/or drift limits to meet the collapse risk target.

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