Structural behavior of reinforced concrete segments of tunnel linings strengthened by a steel-concrete composite

Abstract

Structural defects of existing segmental tunnel linings call for strengthening techniques. This was the motivation for conducting real-scale bearing-capacity tests and computational analysis of strengthened segments by means of a steel-concrete composite (SCC). Two load cases were considered: (i) a sagging moment, resulting in intrados and extrados fibers in tension and compression, respectively, and, conversely, (ii) a hogging moment. The experimental observation has shown that, for both load cases, the strengthened segments failed in a ductile fashion. In case of sagging moments, the strengthening effect of the SCC is characterized by the fact that the yield moment and the post-cracking stiffness of the strengthened segments with a 40-mm-thick SCC are by 393% and 315%, respectively, larger than those of the unstrengthened segments. As for hogging moments, the strengthening effect of the SCC is considerable, albeit less significant than that for sagging moments. The derived formulae allow for description of the structural behavior of the strengthened segments and for quantification of the tractions at the interface between the steel shell and the concrete. Two main conclusions are drawn from the computational analyses: (i) Concerning the increase of the strengthening effect, in case of a sagging moment, an increase of the thickness of the steel shell is more efficient than that of the new concrete. The converse situation occurs in case of a hogging moment. (ii) For a sagging moment, the interface is in shear-tension, whereas for a hogging moment it is in shear-compression.