Assessing the life cycle of existing maritime structures – application to a harbour bridge in Porto port

Abstract

Since the construction industry is the one that bears most expenses, both in financial and environmental terms, it is of the upmost importance that these expenses originate a product with a long term exploitation, so as to mitigate them. Having this problem in consideration, in this paper the bridge located in the north of Portugal, near Porto, in the oil tanker terminal at the Leixões port was studied. This structure is located in one of the most aggressive environments for concrete structures, a maritime zone. The most accepted durability models in the country, related to deterioration induced by sea chlorides penetration, were then implemented. Thereby, it was possible to identify which model better reflects reality, since the structure in analysis is now at the end of its lifetime, after 50 years of service and shows advanced degradation due to chloride attack.

In the context of this work, the structure and the test methods relevant to the theme being studied were described by inspection reports and in situ test results, made available by the Douro and Viana do Castelo Port Authority. From this data it was possible to study the structure deterioration by introducing them into durability models. These models range from prescriptive to performance based approaches, being possible to identify, from the later ones, a deterministic model, based on the Model Code 2010, a semi-probabilistic based on the E465 specification from the Portuguese National Laboratory for Civil Engineering (LNEC) and two probabilistic models, based on the same standards, for which a computer code was developed during this work. Through these deterioration prediction tools, different project scenarios were established, originating a list of minimal concrete covers to ensure 100 years of lifetime to a structure built in the studied exposure zone.