Reliability-based analysis of Lázaro Cárdenas breakwater including the economical impact of the port activity

Abstract

A formulation to assess the reliability and cost of a breakwater, including the economical impact of port operations, is proposed. The limit state function is the stability performance of the core elements and aleatory uncertainties on the wave height and the weight of these elements are considered. Also, epistemic uncertainty on the modeling of the mean wave height is introduced and its impact on the results is appraised by sensitivity analysis. The formulation identifies percentiles for the breakwater reliability providing an opportunity to make conservative decisions by taking into account specific percentiles of the reliability index as an improvement of the traditional consideration of the mean value. Also, target values of the breakwater reliability are calculated from the minimum expected life-cycle cost. In addition, a curve of the breakwater initial cost vs. reliability is proposed, as a tool towards the optimal decision making on design and maintenance. Reliability calculations are performed via FOSM (First Order Second Moments) approximation and MCS (Monte Carlo simulations techniques), the cost of consequences include potential fatalities and the economic loss of maritime and port activities. It is found, for a case study, that the reliability index through FOSM is 2.37, underestimated due to the linear approximation, whereas for MCS the index is 3.7. Sensitivity analysis showed that epistemic uncertainty on the mean wave height and on the core elements mean weight has significant impact on the breakwater reliability index. However, the standard deviation of the core elements weight has a minor impact on these index. 1