Time-dependent risk assessment of combined overtopping and structural failure for reinforced concrete coastal structures

Rising sea levels and increased sea storminess have resulted in higher frequency of wave overtopping and greater magnitude of hydrodynamic action on coastal defenses. The situation has been exacerbated for reinforced concrete coastal structures due to the seawater induced corrosion of reinforcing steel in concrete which reduces the load carrying capacity of the structure. This combined effect has posed higher risk to the public and necessitated a thorough assessment for coastal structures. The present paper introduces a time-dependent reliability method to predict the risk of failures due to the increased wave overtopping and reduced structural capacity, and some basic applications to illustrate its use. A stochastic process is proposed to model the time variant and random nature of severe waves. Also proposed is a structural deterioration model to allow for seawater induced steel corrosion in concrete. It is found in the example that the rising sea levels and increased sea storminess reduce the safety and serviceability of coastal defenses. The method presented in the paper can provide useful information for structural engineers, operators, and asset managers in developing a risk-informed and costeffective management scheme for coastal defenses. The timely maintenance of coastal defenses has the potential to prolong their safe service life