Water-Driven Debris Impact Forces on Structures: Experimental and Theoretical Program

Abstract

Water-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 theoretical 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 were carried out with a wooden utility pole and a shipping container. The tests were carried out in-air, and were designed to provide baseline, full-scale results. A 1:5 scale shipping container model was used for in-water tests in the Oregon State University large wave flume. These tests were used to quantify the effect of the fluid on the impact forces. Results from both experimental programs are presented and compared with theoretical predictions. The analytical predictions are found to be in sufficient agreement such that they can be used for design. A fundamental takeaway is that the impact forces are dominated by the structural impact, with a secondary affect provided by the fluid. Both forces are quantified in the paper.

Estimation of demands resulting from inelastic axial impact of steel debris

“…The impact force for the elastic bar model is obtained from the solution of the one-dimensional wave equation [23,24]. This formulation assumes that the projectile impacts a rigid structure (i.e., k s ?…”

“…Recently, full-scale in-air axial impact tests of a wood utility pole, steel tube and shipping container have been conducted [22]. The main focus was on the elastic behavior of wood poles and shipping containers, and a simplified elastic model for debris impact force estimation was developed [22][23][24][25]. A small-scale model of the shipping container was tested in a wave flume to investigate the effect of water on debris impact forces [23,27]; see also [26] for related experiments and simulation.…”

“…The main focus was on the elastic behavior of wood poles and shipping containers, and a simplified elastic model for debris impact force estimation was developed [22][23][24][25]. A small-scale model of the shipping container was tested in a wave flume to investigate the effect of water on debris impact forces [23,27]; see also [26] for related experiments and simulation. The contribution of water to the debris impact demands was found to be secondary to the ''pure'' structural impact [23,27].…”

“…A small-scale model of the shipping container was tested in a wave flume to investigate the effect of water on debris impact forces [23,27]; see also [26] for related experiments and simulation. The contribution of water to the debris impact demands was found to be secondary to the ''pure'' structural impact [23,27]. In FEMA P646 [9], for a 20-ft shipping container axial impact it is suggested to increase the peak force by 14% to account for the ''hydrodynamic mass'' effect of the fluid.…”

Effect of nonstructural mass on debris impact demands: Experimental and simulation studies

“…The main focus was on the elastic behavior of wood poles and shipping containers and a simplified elastic model for debris impact force estimation was developed [14][15][16][17]. Additionally, an inelastic model was developed and validated by experimental and simulation results to estimate the debris impact demands [18].…”