ABSTRACT
Tunnels typically comprise large scale infrastructure projects, where a demand for an increased service life is present. On the other hand, temporary structures often do not need to be designed for a service life longer than a few years only or they can form part of the permanent structure. In addition to this, the use of composite or combined primary and secondary concrete tunnel linings (considering the conventional tunnelling approach) can significantly influence the CO2 equivalent emissions footprint of tunnel projects – particularly during construction. The present paper discusses a reliability life-cycle based methodology to adjust safety factors used in the design of tunnel linings in order to reach a specified service life, i.e. a variation of the safety factors used leading to an analogous reliability level at the start of the structures’ lifetime, which in turn provides a modification of the expected service life duration. Furthermore, the outcome of this approach is assessed in terms of sustainability under the spectrum of the recently introduced climate-change limit state. The results indicate the possibility to deploy a novel design concept which allows to improve a tunnel structure’s profile holistically, i.e. with consideration of traditional design criteria such as construction costs and structural safety, but also acute future oriented needs such as the service life and the climate impacts of tunnel infrastructure.
