Seismic Performance Evaluation of Novel Segmented Arch bridge

Abstract

This study presents a seismic assessment of a voussoir arch bridge in Delhi, a region with high seismic activity. The arches are comprised of individual concrete voussoirs, which serve as discrete blocks. Interestingly, no binding agents are utilized at the contact joints to connect these blocks. Additionally, these blocks do not have any reinforcement. As a result, the blocks are held together solely by the dry joints. The contacts between the blocks do not possess tensile strength, but this is typically not a concern under serviceability loads as arches primarily endure compression forces and are not subjected to tension. However, it is important to acknowledge that arch sections do experience in-plane shear forces under the effect of serviceability load. The absence of binding agents and dowel action through reinforcement at the joints presents a significant challenge in terms of shear strength and the blocks rely solely on frictional resistance at the contacts to maintain their structural integrity under shear. But, during seismic events, arches can experience both in-plane and out-of-plane tensile forces. This can cause the joints to open up, forming hinges due to rocking of adjacent blocks. If a sufficient number of such hinges are formed, the structure may transition into a mechanism in both the longitudinal and transverse directions. In addition, during an earthquake, there can be a substantial increase in in-plane shear forces and the introduction of out-of-plane shear forces within the arch section. If these forces surpass the frictional shear resistance, it can result in the sliding of adjacent blocks in both the longitudinal and transverse directions. These actions indicate that during earthquake arch’s integrity and global behaviour are predominantly dependent on the stability of the voussoir assemblage rather than material’s inelastic damage. Hence, a 3-dimensional discrete element model (DEM) of the bridge is developed assuming individual voussoirs to be discrete rigid bodies in cohesionless frictional contact. A general-purpose finite element tool ABAQUS is used to develop the DEM. Accuracy of the model is validated by simulating the static and dynamic response of simpler rigid bodies in rocking as well as sliding mode. It is noteworthy that lateral load resisting mechanism of the bridge differ in the in-plane and out-of- plane directions, behaving as an arch and a stack of concrete blocks, respectively. Interestingly both these load resisting systems are severely sensitive to the vertical excitations. Thus, a series of nonlinear time history analysis of is performed under simultaneous excitation using 3 component of earthquake ground motions. The seismic input is based on a set of ground motion records that align with the design spectrum for Delhi city. The seismic performance of the bridge was evaluated by defining distinct limit states of damage in sliding and rocking modes, corresponding to different performance levels. The study and its findings indicate that the investigated voussoir arch bridge is more susceptible to in-plane sliding failure. These results contribute to a better understanding of the bridge and its behaviour under seismic loading and can inform future design and retrofitting strategies for similar structures in seismically active regions.