Vertical Load Path Failure Risk Analysis of Residential Wood-Frame Construction in Tornadoes

Abstract

Since the devastating 2011 tornado season, there has been renewed interest in understanding tornado wind loads and developing methodologies to reduce the risk of tornado damage. This study focuses on the assessment of the system-level performance of five different residential light-frame wood building archetypes subjected to tornado winds. The system-level performance considered three critical components along the vertical load path within each building, namely, the roof sheathing, roof-to-wall connection, and wall-to-foundation anchorage. Although there has been significant work on each of these components independently, combined uplift and lateral forces have received less attention. Therefore, a laboratory testing program for wood shear walls, reported herein, was performed to determine the wall-failure mechanisms and capacities when subjected to combined shear and uplift forces. Each building archetype was designed at varying locations across the United States based on the current residential building code and/or observed practice. Fragilities were developed, based on the assumption that failure of any component along the vertical load path results in failure of the system. Because the forces in each connection along the vertical load path arise from the same tornado wind load, the connection failures are not statistically independent, and Monte Carlo simulation was applied to perform the system reliability analysis.