Structural Failure Modes of Single-Story Timber Houses Under Tsunami Loads Using ASCE 7’S Energy Grade Line Analysis

The structural response of single-story timber houses subjected to the 27 February 2010 Chile tsunami is studied in San Juan Bautista, an island town located nearly 600 km westward from the earthquake’s rupture source, in the Pacific Ocean. The ASCE 7-22 energy grade line analysis (EGLA) is used to calculate flow depths and velocities as functions of the topography and recorded runup. To understand the structural response along the topography, reactions and displacements are computed at six positions every 50 m from the coastline. Houses are modeled using the Robot software, considering dead and live loads cases under the Load and Resistance Factor Design (LRFD) philosophy. The results show that houses located near the coastline experience severe displacements and collapse due to a combination of hydrodynamic forces, drag and buoyancy, which significantly reduces the efficiency of the foundations’ anchorage. Structures far from the coastline are less exposed to reduced velocities, resulting in decreased displacements, structural demand and a tendency to float. Finally, the methodology is validated by applying a nonlinear analysis of the structures subjected to tsunami loads at the different positions considered in this study. Despite their seismic resistance, lightweight timber houses are shown to not be suitable for areas prone to tsunamis. Tsunami-resilient design should therefore consider heavier and more rigid materials in flooding areas and the relocation of lightweight structures in safe zones.