Wave-Current Impulsive Debris Loading on a Coastal Building Array

Waterborne debris impacts during inundation events are a widely observed threat to structures in coastal communities. This study investigates the probability of impact and magnitude of wave-current (N = 1,170) and current-only (N = 156) debris events on exposed and sheltered buildings within a 10 x 10 building array, using laboratory measurements of structural loading response, flow hydrodynamics, and video recordings of flow transport and impact. A methodology based on a structural system with a single degree of freedom is implemented to estimate the applied debris impulse from collisions and to investigate the dynamic impact of waterborne debris on structures. Results show that the debris collision probability varies greatly, between 42% for unsheltered rows and 2% for nine rows of sheltering. Given a collision, the normalized debris impulse in sheltered buildings is at maximum 0.8 times the impulse for unsheltered conditions, and this reduction increases as the number of sheltering rows increases. Using empirical exceedance probabilities of the applied debris impulse, a framework is developed to estimate the maximum structural loading response within a building array, along with a comparison with data and existing standards. The effect of the impact duration on the relation between the applied debris impulse and the maximum structural response is also discussed.