Prediction of service life of existing structures by applying probabilistic service life design (SLD) procedures

Due to bad experiences corresponding with very costly maintenance and repair measures on existing structures, durability issues of reinforced and pre-stressed concrete structures receive more and more attention from the operator/owner. In order to minimise costly repair or globally spoken to optimise a structure from the economical point of view, considering the planning-, construction- and utilisation-phase, a new service life design concept for reinforced concrete structures has been developed within an European funded Brite-Euram research project DURACRETE [1]. This new concept enables designers to perform a fully probability based service life design (SLD), always related to relevant (exposure dependent) limit state formulations. This method gives the contractor/operator/owner the possibility not only to target the durability of new structures but also to assess the performance of already built structures with regard to durability. If the required reliability can not be achieved by the actual structural lay-out of an already existing structure in consequence further inspection/monitoring and/or intervention (maintenance, repair, strengthening) might be necessary to control/increase the structural reliability. This paper illustrates the effects of different options concerning the thereby increased reliability of the already existing structure.