Reliability-based formulation of building vulnerability to debris flow impacts

Abstract

Physical building vulnerability to debris flows is defined as the potential damage degree of buildings for a given debris-flow intensity. In this paper, the physical characteristics on both debris flow intensity and building response are considered. Uncertainties in building capacity and debris flow intensity are explicitly quantified to evaluate the damage probability of a typical reinforced concrete building subject to debris flow impact. Four damage states with clear failure mechanisms are defined using multi-source information from field observations, numerical simulation and expert experience. Two series of fragility models have been proposed based on practical debris-flow impact pressure models. Several debris flow intensity measures are investigated. A better indication can be provided using the intensity measure that represents specific failure mechanism, for example, impact force (hv2) for force-dominated failures or overturning moment (h2v2) for moment dominated failures, where h and v are debris flow depth and velocity, respectively. The corresponding fragility surfaces best express the potential building damage. The intensity thresholds in the proposed fragility curves are consistent with those in empirical vulnerability curves. The methodology presented in this paper promotes the vulnerability assessment using physics based modeling, leading to a more reliable evaluation of building damage caused by debris flows.

Physical vulnerability of reinforced concrete buildings under debris avalanche impact based on GF-discrepancy and DEM-FEM

“…Figure 11, where the dispersion of the results makes it difficult to find a representative vulnerability curve; this problem has also been encountered by Luo et al (2022).…”

“…The velocities of debris avalanches produced by landslides range from several meters per second to hundreds of meters per second; we only consider impact situations with relatively low mass flow speeds because of the strong destructive nature of high-speed debris flows. The velocity and height of a debris event in a flow channel are generally assumed to follow a uniform distribution (Luo et al 2022), with the velocity range a debris flow being 1-12 m/s (Table 5). Usually, when the height of a debris flow exceeds the height of the building, resulting in the building being completely buried, it is assumed that the building is completely destroyed, losing its value in the vulnerability assessment.…”

“…After determining the damage status of each case, we first divided every intensity indictor into several continuous intervals and calculated the probability of occurrence of the different damage levels, namely, the damage probability , which was obtained by dividing the total number of cases in the same damage level by the total number of cases falling within that interval. Then, the exceedance damage probabilities of the different intensity indictors ( , , , and , which were used by Luo et al (2022)) were calculated using the equations listed in Table 9 with intervals of 3 m 2 /s, 12 m 3 /s, 0.1, and 0.15, respectively. In the expression of , and are the limit of the velocity in the study and the Froude number defined as , that is, the ratio of the inertial force to the gravity.…”

“…These authors used numerical methods to provide accurate simulation data, saving a large amount of on-site investigation time; however, the interaction process between debris flows and buildings has been ignored to a certain extent. Interestingly, this issue attracted the attention of Luo et al (2022), who established a simplified equivalent impact model in which the impact force is estimated via hydrodynamic models with uniform (Figure 1 the uncertainties of the debris in an explicit manner. Although interactions between debris flows and buildings have been considered, true dynamic contact models, in which the impact force is a variable value over time rather than a constant, have not yet been applied to vulnerability assessments of buildings impacted by debris flows because of the large computational costs, both in time and money.…”

“…However, one important issue needs to be addressed: how can real debris flow impact scenarios with samples, including all of types of impact cases, be selected as accurately as possible considering the uncertainties of debris flows (Luo et al 2020, Luo et al 2022. The most commonly used sample methods to solve this problem are Monte Carlo simulation (MCS) and Latin hypercube sampling (LHS), which has been widely used in probability analyses (Shields et al 2016).…”