Stressing sequence of steel cable-stayed bridges built by cantilevering

Abstract

The construction of cable-stayed bridges by cantilevering implies several changes of geometry, stress and strain patterns during the assemblage of segments. The main target to be satisfied in the construction process is the achievement of the required final geometry and of a convenient state of stress for self-weight and sustained loads. The sequence of stay stressing and the values of prestressing forces at each stage of segment assembling have the main role for reaching the desired result of design, due to the large redundancy of cable-stayed structures.Among the different procedures proposed in the literature for initial cable force determination, the Partial Elastic Scheme (PES) Method has been already applied to cable-stayed bridges of small-medium spans. In this study the same methodology is extended to cable-stayed bridges with larger spans and steel decks, by considering the effects of geometric nonlinearity attributable to the cable sag. In this paper PES method is modified to take into account the axial stiffness of stays and the related nonlinear behaviour of the bridge. Nonlinear analyses are performed with forward staged-construction finite element procedures and different strategies for establishing the initial value of stay stressing at each stage are proposed and compared. A case-study is investigated applying different approaches of stressing sequence. Results show the applicability of PES method to large cable-stayed bridges, when nonlinear staged construction analyses are performed and initial prestressing axial forces are found by linear partial elastic schemes.