A series of experiments have been carried out in the large wave flume (LWF) at Oregon State University to quantify tsunami bore forces on structures. These tests included "offshore" solitary waves, with heights up to 1.3 m, that traveled over aflat bottom, up a sloping beach, and breaking onto a flat reef. Standing water depths on the reef varied from 0.05 m to 0.3 m. Resulting bores on the reef measured up to approximately 0.8 m. After propagating along the reef, the bores struck a vertical wall. The resulting forces and pressures on the wall were measured. The test setup in the LWF is described, and the. experimental results are reported. The results include forces and pressure distributions. Results show that the bores propagated with a Froude number of approximately 2 and that the forces follow Froude scaling. Finally, a design formula for the maximum impact force is given. The formula is shown to be an improvement over existing formulas found in the littérature.
A series of experiments have been carried out at Oregon State University to quantify tsunami bore forces on structures. Phase 1 of the tests was carried out in the Tsunami Wave Basin (TWB), while Phase II of the tests were carried out in the Large Wave Flume (LWF) at approximately twice the scale of the Phase I tests. These latter tests included ‘offshore’ solitary waves, with heights up to 1.3 m, that traveled over a flat bottom, up a sloping beach and breaking onto a flat ‘fringing reef’. Standing water depths on the reef varied from 0.05 m to 0.3 m. Resulting bores on the reef measured up to approximately 0.8 m. After propagating along the reef, the bores struck a vertical wall. The resulting forces and pressures on the wall were measured. The test setup for the Phase II tests in the LWF is described and the experimental results are reported. The results include forces and pressure distributions. Results show that the bores propagated with a Froude number of approximately 2, and that the forces follow Froude scaling. Finally, a design formula for the maximum impact force is given. The formula is shown to be an improvement over existing formulas found in the literature. The lateral forces are shown to be quite significant compared to traditional lateral loads on vertical wall elements.
Debris driven by tsunamis pose a significant threat to structures, and yet most building codes that include debris impact are based on rigid-body dynamics. However, the debris will most likely not be rigid compared to the structural components, such as walls and columns, that they impact. Impact by flexible, water-borne wood poles and shipping containers is considered in this paper. A relatively simple one-dimensional model for acoustic wave propagation, for which an analytical solution is obtained, is shown to provide a good estimate for the initial impact force and duration. This model is validated with small-scale, in-air tests. The simple model is also validated with two-dimensional fluid-structure interaction using a finite element code. The acoustic model works well for initial impact as long as the debris rebounds from the impact target. When the water prevents separation, then the acoustic model significantly overestimates the asymptotic force. The effect of the gravitational waves resulting from impact is to retard re-impacts, as compared to the acoustic model.
In active control of structures, it may be necessary to determine real-time displacements from measured deformations. Recently an inverse finite element method, iFEM, has been proposed to recover ‘small’ displacement fields for plate and shell structures from (small) strain measurements. A procedure to handle large displacements and nonlinear strains is presented in this paper. A similar least-squares error functional as in linear iFEM is used, but the linear strains are replaced with the Green-Lagrange strains, and a ‘total Lagrangian’ formulation is developed. As in the linear iFEM, the focus is again principally towards plate and shell structures. The functional is minimized with the finite element method. The nonlinear iFEM formulation is presented in detail and applied to a cantilever beam undergoing very large displacements. The relatively simple example is used to explore the formulation’s performance to recover large displacements. The results indicate that the approach is able to recover the large displacement field. Additional work is required to develop the method for practical application.
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