Balancing protection and risk: Understanding the dual impact of trees on low-rise buildings during extreme wind events

Abstract

This study investigates the dual role of trees in either mitigating or exacerbating wind-induced damage to low-rise buildings during extreme wind events. Trees can act as natural windbreaks that reduce wind loads, but they also pose significant risks when uprooted or broken. To explore the shielding aspect, large-scale wind tunnel tests were conducted at the Natural Hazards Engineering Research Infrastructure (NHERI) Wall of Wind (WOW) Experimental Facility. Four 1:20 scale T-shaped low-rise building models surrounded by various tree densities were tested, and wind pressures were measured across multiple directions. The results showed that trees can reduce localized peak pressure coefficients by over 50 % in certain orientations but may intensify them in others.

To quantify the risk of tree-induced damage, a built-in house Monte Carlo Simulation-based probabilistic framework was introduced. This model estimates tree failure probabilities and resulting building damage by accounting for wind speed, direction, and tree characteristics. A case study demonstrated how tree placement and wind direction critically influence damage likelihood. Fragility curves were derived to identify wind angles at which trees offer protection versus when they pose hazards. The findings of this study highlight the importance of considering both the protective and damaging effects of trees in risk assessment models. The study offers insights for enhancing urban planning and improving disaster resilience in tree-populated communities.