Structural behaviour of segmental concrete continuous bridges with unbonded prestressing and dry joints

This work presents a finite-element method (FEM) analysis of the behaviour of continuous segmental concrete bridges with external prestressing and dry joints, focusing on the response under combined shear and flexure, at the service limit state (SLS) and at the ultimate limit state (ULS). A previously validated FEM model has been applied to simulate the structural behaviour of continuous bridges until failure. A geometrically non-linear analysis has been performed, where the particular behaviour of the dry joints, the concrete plasticity and the slipping of the prestressing tendons at the deviators have been considered. Results of the analysis have been compared with the available data of the modelling of simply supported bridges, and the different behaviour introduced by the support redundancy has been pointed out. Analysis proves that the SLS can govern the design of the prestressing force, whereas in simply supported bridges, it is the ULS that always governs the design. Concrete and steel remain essentially linear under ultimate loads, which implies that there is an extra safety factor against failure. Before failure, when support and mid-span joints are opened, moment redistribution has occurred and an arch springing from the bearings is formed within the concrete, which equilibrates the external loads.