Collaborative Research: Experimental Quantification of Tsunami-driven Debris Damming on Structures

This project will investigate how the accumulation of debris in front of buildings, i.e., debris damming, during tsunami events leads to an increase in the forces imposed by tsunami flow on structures. To better understand the magnitude of increase in tsunami forces due to damming, the mechanisms that cause increased forces, and the variability in damming loads, experiments will be conducted on elevated buildings in the large wave flume at the National Science Foundation (NSF)-supported Natural Hazards Engineering Research Infrastructure (NHERI) facility at Oregon State University.

A better understanding of tsunami-driven debris damming loads can be used to (1) improve existing design guidelines to construct safer buildings, (2) identify factors that affect debris damming to determine measures that help reduce or mitigate the damming loads, and (3) improve tsunami vulnerability assessment of existing buildings for characterizing risk and resilience. The project will also include outreach activities to engage high school students in the experiments, research opportunities for undergraduate and graduate students to participate in the experiments and computational modeling, and webinars for researchers and practicing engineers to promote the adoption of the research findings.

This research will contribute to the NSF role in the National Earthquake Hazards Reduction Program (NEHRP).

The experiments in the large wave flume will focus on identifying the mechanisms that cause tsunami-driven debris damming and associated loads on the first floor columns of an elevated structure, such as a vertical evacuation structure. These mechanisms include, but are not limited to, debris-structure, debris-flow, debris-debris interactions, changes in flow and velocity fields, and changes in effective building projected area.

The experiments will use homogeneous debris as well as non-homogeneous debris mixtures with varying shapes, sizes, densities, and quantities. A novel iterative experimental design strategy will be used to address the exponentially large number of potential experimental conditions and to quantify the aleatory uncertainty in the loads. Additionally, new dimensionless parameters will be used to quantify the likelihood of damming and the probability of exceeding design damming loads.

The results from the analysis of experimental data and supplementary computational fluid dynamics simulations will provide new knowledge on how debris interacts with other debris and the structure, and how tsunami flow fields (speed and depth) change because of debris damming. The resulting data set will be shared with the research community via the NHERI Data Depot (https://www.DesignSafe-ci.org).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.