Probabilistic assessment of the durability performance of concrete structures

Abstract

In recent years, much research work has been carried out in order to obtain a more controlled durability and long-term performance of concrete structures in chloride containing environments. In particular, the development of new procedures for probability-based durability design has proved to be very valuable. In order to provide more data and experience with probability-based durability design, two relatively new concrete structures in Norwegian harbours were selected for detailed investigations in the field and subjected to durability analysis. For each structure, the field investigation included a large number of chloride penetration measurements, electrochemical surface potential mapping and measurements of concrete cover. The equation used for modelling of the chloride penetration was based on Fick’s Second Law of Diffusion in combination with a time dependent diffusion coefficient. The probability analysis of the durability performance was performed by use of a Monte Carlo Simulation. For the most exposed beam elements, the durability analysis showed that the probability of failure in the form of onset of steel corrosion exceeded 10 % within a period of 10 to 15 years, while the field investigations revealed that the chloride front had already reached a depth varying from 40 to 50 mm after a service period of 7 to 8 years. For the most exposed anchor slab, a 10 % probability of failure was exceeded within a period of 10 years, while a depassivation of the embedded steel had already taken place after 8 years. If a probability-based durability design had been carried out as an integral part of the original design of the structures, such a poor durability would probably not have been acceptable.