Seismically Resilient Bridge Columns with Polyurethane-Enhanced Damage-Resistant (DR) Joints and Replaceable Energy Dissipating (ED) Links

Abstract

In this dissertation, the concept of seismically resilient bridge columns with polyurethane (PU)-enhanced damage-resistant (DR) joints and replaceable energy dissipating (ED) links is proposed. The proposed system introduces the component of explicit damage control and accelerated low cost post-earthquake retrofit/repair in the design of bridges for moderate to high seismicity regions; hence, expanding the focus of the bridge engineering community from ABC to ABC&AR, where AR stands for “accelerated retrofit/repair”. PU-enhanced column with ED links offer: (i) explicit damage control through PU damage-resistant end segments (ii) self-centering through internal unbonded post-tensioning, (iii) energy dissipation and flexural stiffness/strength through external replaceable ED links. The mechanical properties of selected PU materials with various compositions, was characterized through a comprehensive experimental program accounting for environmental conditions, loading conditions, and long term effects. The performance of the proposed system was assessed through three-dimensional finite element analysis for various PU segment geometries and various ED link properties in terms of strength, stiffness, ductility capacity, energy dissipation properties, self-centering capabilities, and damage resistance. Novel uniaxial visco-elastic/plastic constitutive models were developed capable of capturing the salient response features of the selected PU materials. The constitutive; models were calibrated using the test data. The developed constitutive models are implemented in the OpenSEES structural analysis software. Seismic performance of the proposed system was assessed through numerical models of the proposed system generated in OpenSEES structural analysis software. The monotonic and cyclic response of the proposed system was investigated and compared with the response of a conventional reinforced concrete (RC) monolithic and rocking column. Moreover, the seismic performance of the proposed system was investigated via fragility analysis accounting for various damage states. The performance of the proposed system was experimentally evaluated and compared to a conventional RC rocking column through large scale (~1:1.25) quasi-static cyclic tests. Finally, the performance of the numerical models was validating with the test data. In summary, the proposed column design demonstrated a high ductility capacity associated with the damage in the replaceable ED links and the minor or no damage in other components of the system, and high re-centering capacity upon releasing/removing the ED links.