The physical vulnerability of different types of building structure to debris flow events

Vulnerability assessment of elements at risk is a key component for risk assessment. The representative element at risk for debris flow is a residential building in downstream mountain, and the physical vulnerability of such a building depends on the structural characteristics of a building. The main objective of this paper was to construct physical vulnerability curves for different types of building structures in Korea to enable a quantitative assessment of debris flow risks. The physical characteristics of debris flows were analyzed based on 11 debris flow events that occurred in July and August, 2011. A total of 25 buildings that were damaged during these events were investigated in detail to determine the characteristics and patterns of damage. This study analyzes the relationship between the degree of building damage and the intensity of the debris flows through field survey data, spatial data, and empirical formula. Three different empirical vulnerability curves were obtained as functions of the debris flow depth, the flow velocity, and the impact pressure. Furthermore, the vulnerability function was characterized according to the structural type of the buildings. In the case of non-RC buildings, complete destruction occurred with an impact pressure greater than 30 kPa. For RC buildings, slight damage occurred with impact pressures less than 35 kPa. The impact pressure of debris flows corresponding to slight damage to RC buildings could result in complete destruction of non-RC buildings. The physical vulnerability curves suggested here have potential applications in quantitative assessment of the structural resistance of buildings to debris flow events.