Multi-span steel–concrete bridges with anti-seismic devices: A case study

Abstract

Seismic protection for structures in general, and bridges in particular, is very complex. Indeed, any analysis of bridges with fluid viscous dampers and shock transmitting devices must be completed using a sophisticated finite element (FE) model. Furthermore, a large number of factors must be accurately considered and followed in order to effectively and efficiently protect human life. When dealing with complex structures, as is the case of the viaduct under examination, which contains numerous devices, the starting point is an assessment of the consistency of fluid-viscous dampers and shock transmitters integrated with bearings. This paper, a case study of design and static-dynamic testing procedures on multi-span steel–concrete viaduct provided with fluid viscous dampers and shock transmitters devices, deals directly with this process. To these ends, the FE modeling of the viaduct required an updating procedure model to ensure optimization. Those viaducts built during the “Caltagirone Project,” can be defined as works of great interest due both to the construction methods adopted and to the techniques of stress control during the seismic stage. The design process allowed a rectification of those seismic issues deriving from structural irregularities (altimetric and planimetric), as well as from the high seismicity of the area. The analyses were carried out using a Capacity Design approach, employing non-linear seismic dissipative devices integrated as supports while validating that the substructures are maintained substantially elastic. For this reason, the piers were modeled on their non-linear behavior using Takeda's hysteretic model. Moreover, fluid viscous dampers and shock transmitters integrated with bearings were designed in accordance with the substructures' different stiffness; this partially dissipates those stresses induced by earthquakes, in order to keep the deck and the substructures substantially elastic, establishing a Life-Safety Limit State condition (at the Ultimate Limit State—ULS). The verifications carried out demonstrated the capability of structures to withstand stresses under the Collapse Limit State (CLS) condition without damage and at the same time to ensure the curvature capability from the piers. The comparisons between experimental and numerical results together with the demanding qualification tests carried out by this study demonstrate that the hydraulic devices are an efficient solution to assess seismic stresses induced on the viaduct and in its substructures, confirming the reliability of the aforesaid devices, thus ensuring better structural safety.