Multi-hazard vulnerability of buildings to debris flows

Landslide hazards often occur in succession with multiple hazardous processes. The elements at risk such as buildings are therefore exposed to a multi-hazard environment. Multi-vulnerability assessment is a critical component of multi-hazard risk analysis. In this paper, effect of hazard interactions on the physics of building damage is formulated from the perspective of triggering and temporal relations. A fragility analysis framework for generating physics-based vulnerability models for sequentially and concurrently occurring hazards is proposed. Monte Carlo simulation is used in the framework to include the uncertainties from both hazard intensity and building properties. The framework is illustrated by evaluating the failure probability of a typical reinforced concrete building impacted by multiple surges of debris flows. Considering specific debris flow-building interaction mechanisms, nonlinear finite-element pushover analysis is adopted to obtain the building response under debris flow impact. By quantifying the physical damage caused by the primary debris flow, the cumulative damage effect of the sequentially occurring debris flows is formulated. The amplified damage effect of the concurrently occurring debris flows is however case specific. The proposed methodology shows potential to address more complex multi-hazard scenarios and enhance the multi-vulnerability assessment, filling the research gap on multi-vulnerability assessment for landslide hazards.