Forensic study of structures for durability

Abstract

Structural durability is becoming an important issue of forensic engineering. General principles on probabilistic approach to structural design for durability are provided in a newly developing international standard ISO “General Principles on the Design of Structures for Durability”. It appears, however, that the operational use of the new procedures in practice would require additional studies focussed primarily on forensic criteria, physical models of material deteriorations, and theoretical models of basic variables. It is shown that forensic criteria should be differentiated taking into account the character of the relevant limit state, consequences of its infringement and costs of safety measures. Three limit states are distinguished in general: initiation limit state, serviceability limit state and ultimate limit state. Probabilistic methods of cost optimisation are used to provide background information facilitating specification of appropriate target reliability levels. General principles on forensic assessment of structures for durability are illustrated on an example of a reinforced concrete members exposed to carbonation. It is shown that the total cost of the member including cost of durability failure depends on the thickness of the concrete cover, design service life and discount rate. The optimum concrete cover increases