Collapse mechanism and robustness of precast segmental bridges

In the construction of multi-span precast concrete segmental bridges, in situ stitches are often cast to connect together adjacent cantilevers assembled from precast segments. Since the stitches are often lightly reinforced, the robustness of a segmental bridge could be adversely affected by the capability of the stitches to resist any large variations in moment during extreme events. While most previous studies have focused on methods to measure robustness, there has been little systematic examination of the effects of strength and behaviour of structural components on robustness of structures. As prestressed concrete is relatively non-ductile, finite-element analyses are carried out taking into account the full-range non-linear moment–curvature relationship to examine the formation of plastic hinges and possible collapse mechanisms. Three classes have been proposed for the evaluation of robustness, namely superb, adequate and inadequate. Recommendations to achieve good robustness are also put forward.