Reliability study on uncertainty parameters and flood duration on scouring around unprotected and protected bridge piers

Abstract

ABSTRACT Empirical equations for predicting local scour depth around bridge piers only consider the effects of hydraulic parameters and do not take into account the uncertainties involved in them. Empirical equations also assume steady-state condition which means the flood peak flows for a long time. In the present study, a methodology is presented for the reliability assessment of bridge piers against scouring considering the uncertainties involved in effective parameters and duration of the flood. Additional necessary experimental studies were also carried out to develop an equation for time development of scouring around a protected pier by a collar. Monte Carlo simulation technique was used for estimating the probability of bridge failure. In addition, Fault Tree analysis was employed for combining the interactions of various parameters and calculating the overall probability of failure. For unprotected piers, results showed that at lower flow intensities, flood time has a lower influence on probability of bridge failure. It was also concluded that the collar protection increases the reliability of bridge piers significantly, especially at lower flow intensities. Furthermore, the model was applied to find a relationship between the reliability index and safety factors under various flow conditions.