Parametrized Wind–Surge–Wave Fragility Functions for Wood Utility Poles

Abstract

Wood poles are among key components of the overhead grid infrastructure that are highly vulnerable to wind hazards. In coastal regions where hurricanes are often accompanied with a storm surge, in addition to high wind pressure, poles may experience significant surge and wave loads with the potential of triggering multiple failure mechanisms. However, multihazard pole fragility models that consider various modes of failure are lacking. This paper proposed a set of parameterized fragility models that are a function of wind-, surge-, and wave-related intensity measures and properties of poles. For this purpose, a design of experiment was conducted to generate realizations of intensity measures and pole-specific deterministic and uncertain parameters. For each realization, the state of survival/failure of pole was estimated for each mode of failure. Subsequently, for each class of pole and soil type, a logistic regression was carried out to generate fragility models for pole rupture at the ground line and pole overturning due to foundation failure. The results indicated that both pole rupture and foundation failure can be significant modes of failure conditioned on the type of soil. For example, for medium-strength cohesive soils, both modes of failure were significant, whereas for very-stiff-strength cohesive soils, pole rupture was the dominant mode of failure. The results of this study are key for risk and resilience analysis of coastal electric power systems and provide useful insights for decision making and risk management processes.