Experimental and Analytical Study of Water-Driven Debris Impact Forces on Structures1

Abstract

Experim ental and Analytical Study of W ater-D riven Debris Im pact Forces on Structures1Water-driven debris generated during tsunamis and hurricanes can impose substantial impact forces on structures that are often not designed for such loads. This paper presents the design and results of an experimental and analytical program to quantify these potential impact forces. Two types of prototypical debris are considered: a wood log and a shipping container. Full-scale impact tests at Lehigh University (LU) were car ried out with a wooden utility pole and a shipping container. The tests were carried out in-air. The purpose of these tests was to provide baseline, full-scale results. Because of size limitations, a 1:5 scale shipping container model was used for in-water tests in the Oregon State University (OSU) large wave flume. These tests were used to quantify the effect o f the fluid on the impact forces. Results from both experimental programs are pre sented and compared with analytical predictions. The predictions are found to be in suffi cient agreement such that they can be used for design. A fundamental finding is that the impact forces are dominated by the structural impact, with a secondary effect provided by the fluid. Both forces are quantified in the paper.

NHERI Lehigh Experimental Facility With Large-Scale Multi-Directional Hybrid Simulation Testing Capabilities

“…The tsunami debris impact force testbed is used to study waterborne debris impact forces on structures (Riggs et al, 2014). The testbed is shown in Figure 2C, where impact forces from a cargo shipping container are being investigated.…”

“…(2) large-scale real-time hybrid simulation (RTHS), which is a HS conducted at the actual time scale of the physical models and excitations (Chen et al, 2009;Karavasilis et al, 2011;Chae et al, 2014;Dong et al, 2015); (3) large-scale real-time hybrid simulation with multiple experimental substructures, where several experimental specimens are used in an RTHS (Chen and Ricles, 2012;Al-Subaihawi et al, 2020); (4) geographically distributed hybrid simulation (DHS), which is an HS with physical models and/or numerical simulation models located in different laboratories and connected through the internet (Ricles et al, 2007); (5) geographically distributed real-time hybrid earthquake simulation (DRTHS), which combines DHS and RTHS (Kim et al, 2012); (6) dynamic testing (DT), which use high speed servo-controlled hydraulic actuators at real-time scales to impose predefined force or displacement histories (Ricles et al, 2002a;Chae et al, 2013b;Riggs et al, 2014); and (7) quasi-static testing (QS) of physical models using predefined force or displacement histories (Ricles et al, 2002b;Zhang and Ricles, 2006;Perez et al, 2013). A broad array of instrumentation, large-scale data acquisition systems, and advanced sensors is available to acquire the system-level data needed to support the goal of advancing computational modeling and simulation.…”

Tsunami-Driven Debris Motion and Loads: A Critical Review

“…The study found very little difference in the peak impact force between the in-air and in-water tests. Moreover, Riggs et al (2014) determined that the difference in impact force between the in-air and in-water tests was unaffected by the debris impact velocity. Based on these findings, Riggs et al (2014) did not support the use of the added mass coefficient in the evaluation of debris impact force.…”

“…Moreover, Riggs et al (2014) determined that the difference in impact force between the in-air and in-water tests was unaffected by the debris impact velocity. Based on these findings, Riggs et al (2014) did not support the use of the added mass coefficient in the evaluation of debris impact force. However, Shafiei et al (2016) performed a similar study examining the effect of the added mass coefficient with denser debris and found the peak impact force to be up to 1.5 times greater in-water than in-air.…”

“…More research is needed to determine if the added mass coefficient is necessary in the design for debris impact at full scale. Aghl et al (2014) expanded upon the work by Riggs et al (2014) to develop a 1-D bar model that accurately estimated the impulse demand of a debris impact event. The model considered the structure to be rigid, therefore the impact force which was fully dependent on the properties of the debris.…”