Bridges play an important role in society, especially during the post-earthquake period that enables emergency vehicles and traffic for safe egress and ingress to minimize the loss of property and life. However, some past earthquakes have resulted in large horizontal displacements on the superstructure that have lead to unseating of bridge spans and unexpected pounding forces that damaged critical components such as bearings and anchor bolts. To this end, a new bearing system, referred to as a stopperbearing system (SBS), is proposed as one solution to address the vulnerability of bridge bearings and other components. The horizontal displacement of a deck can be limited to a desired range using the SBS. The nonlinear load-deformation behavior of the SBS is obtained from ABAQUS and used to define the SBS within reinforced concrete analytical bridge models developed in SAP2000, which are subjected to the 1999 Chi- Chi, Taiwan earthquake ground motion (1.01g - E-W component and 0.43g - N-S component). The results from the nonlinear time history analyses show that the SBS is effective in limiting bridge deck displacements and pounding effects. Preliminary analytical modeling of the SBS shows promise as a solution to displacement control of bridge decks for overall enhancement of bridge performance during seismic events.

The feasibility of using superelastic shape memory alloys in the retrofit of multiple frame bridges is investigated. First, three shape memory alloy constitutive models with various levels of complexity are compared in order to determine the significance of including subloops and cyclic loading effects on the structural response. The results show that the structural response is more sensitive to the shape memory alloys strength degradation and residual deformation than the sublooping behavior. Next, two parametric studies are conducted to explore the sensitivity of hinge opening to the mechanical behavior of the superelastic shape memory alloys. The first study is focused on the hysteretic properties of the alloy that could vary depending on the chemical composition or the manufacturing process of the alloy, while the second study targets the changes in the mechanical behavior of shape memory alloys resulting from the variability in the ambient temperature. The results show that the hysteretic behavior of shape memory alloys has only a slight effect on the bridge hinge opening as long as the recentering property is maintained. A detailed study on the effect of temperature shows that a reduction in the ambient temperature tends to negatively affect the hinge opening while an increase in temperature results in a slight improvement. Next, a parametric study is conducted to examine the effectiveness of shape memory alloy retrofit devices in limiting hinge openings in bridges with various properties. In addition, a comparison is made with other devices such as conventional steel restrainers, metallic dampers, and viscoelastic solid dampers. The results illustrate that superelastic shape memory alloys are superior in their effectiveness compared to other devices in the case of bridges with moderate period ratios and high level of ductility, especially when subjected to strong earthquakes.