ABSTRACT
A hybrid connection has been developed for prefabricated concrete bridge superstructures by combining unbonded longitudinal post-tensioning and axial mild steel dissipaters. The connection aims to increase energy dissipation, introduce self-centering and improve overall structural performance during seismic loading. It can be used as an alternative to seismic isolation, resulting in reduced maintenance costs. The connection was tested in a large-scale precast concrete bridge specimen at the University of Canterbury. The specimen exhibited a desirable flag-shape hysteretic response when subjected to transverse quasi-static cyclic loading. The experimental results were extrapolated to various bridge geometries and design target values through parametric analysis. The effects of superstructure beam type, length of bridge, number of spans and target ductility on the transverse force-displacement relationship of the superstructure configurations was investigated. The structures were designed using a direct displacement-based (DDBD) method and analyzed with a modified version of the revised monolithic beam analogy (rMBA). The results show that higher target ductility values decrease the superstructures’ secant stiffness, increase their fundamental period and significantly reduce the base shear and necessary reinforcement ratio (for both mild steel dissipaters and post-tensioning). For low ductility levels (μ=1) greater superstructures lengths generally result in higher ratios of base shear demand to seismic weight due to their larger seismic mass. However, as target ductility levels increase, the secant stiffness of the structures decrease, and greater superstructure lengths result in a decrease in the ratio of base shear demand to seismic weight. Finally, an expression to find the equivalent viscous damping in dissipative rocking superstructures was found by calibrating results from the parametric analysis to theoretical values.
