Numerical evaluation of tsunami debris impact loading on wooden structural walls

Abstract

Water-based disasters such as tsunami, hurricane, and flood can cause significant structural damage to coastal areas and ultimately result in human and socioeconomic losses. Recent studies have highlighted the difficulties associated with estimating tsunami impact loads on residential structures with greater challenges pertaining to estimating the debris impact loads. The main challenges are associated with large variations in debris mass, shape, velocity, and impact angle. According to FEMA P-646 [1], although impact of floating debris is required to be considered by the codes, the added mass of water behind the debris and/or the potential for damming when debris is blocked by structural elements are ignored. Additionally, there is a lack of 3D numerical models that can accurately predict debris impact loads. Due to the three-dimensional dynamic nature of the problem, coupled with highly variable factors affecting debris loads, a 3D finite element (FE) analysis is necessary to determine the debris impact on structures as accurately as possible. To date, one of the major obstacles in modeling tsunami impact on structures is the intense computational demand linked with such models. This paper presents the formulation of an efficient 3D FE model with computational fluid dynamic (CFD) capabilities to study debris impact on interior and exterior wood structural panels. Several important parameters such as initial water volume, water velocity, debris shape, and debris density are varied throughout the analysis in order to determine the individual effect of each parameter as well as the overall effect on wood structural walls. The results for an interior wall panels showed that contribution from water height and velocity is more significant the debris mass in the impact force as water height and velocity increase. Additionally, as the water height increases, the impact force due to debris decreases for an interior panel when debris mass is constant. An exterior panel is significantly closer to a rigid structure, therefore, an increase in impact force due to debris is observed with the increase in water height and debris mass. The results can be used by engineers to estimate debris impact load on wood panels with similar dimension and material properties.