Resilient Earthquake-Resistant Bridges Designed for Disassembly
AuthorVarela Fontecha, Sebastian
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Ordinary reinforced concrete (RC) highway bridges complying with current seismic design provisions are expected to be severely damaged during a strong earthquake. Previous earthquakes have shown that closing a bridge for repair or having to replace the bridge because of extensive damage and permanent tilting of the structure can be very costly and detrimental to the transportation in major urban areas.When RC bridges reach their useful life, only a small portion of the concrete and steel debris from demolition is recycled, while the rest goes to landfills. This is not the ideal end-of-life for construction materials because their extraction and manufacturing emits greenhouse gases, consumes energy, and depletes natural resources, all of which are negatively affecting the environment.In an attempt to link seismic resistance and resiliency with sustainability in bridge engineering, a new generation of earthquake-resistant and resilient highway bridges designed for disassembly (DfD) was developed in this study for the first time. The global objective of developing these bridges is to (1) minimize the economic impact of losing bridge functionality after strong earthquakes, and (2) reduce the environmental impact of producing new construction materials.The new bridge concept first involved the development and shake-table testing of three 1/4-scale deconstructible column models under simulated strong near-fault motions from the 1994, Northridge, California earthquake. The models were then disassembled and inspected, and subsequently reassembled and retested. Three replaceable plastic hinge elements and connections were developed incorporating advanced materials such as engineered cementitious composite (ECC), shimmed flexural rubber bearings, Nickel-Titanium (NiTi) and Copper-Aluminum-Manganese (CAM) superelastic shape memory alloy (SMA) bars, and prefabricated fiber-reinforced polymer (FRP) tubes were integrated in the column models. An additional cast-in-place column combining ECC and CAM SMA was designed and tested to develop an insight into the behavior of large-scale CAM-reinforced members under seismic loading before this type of SMA was adopted in the replaceable plastic hinge elements. The tests confirmed the feasibility of DfD columns. The experimental investigation was then complemented by analytical studies in OpenSees, in which analytical models were developed to replicate the measured response of the column models.To determine the feasibility of the columns within a bridge system, a 1/4-scale, three-bent, two-span bridge model was designed, constructed and tested under simulated near-fault earthquakes on three shake-tables. Upon successful performance of the original bridge, the bridge model was disassembled, all the components were inspected, and the bridge was subsequently reassembled and retested. Extensive evaluations of the behavior of the columns, connections, plastic hinges, as well as the entire system were made during the experimental investigation. The performance of the reassembled bridge demonstrated the feasibility of the proposed elements in a bridge system. Analytical studies using OpenSees were also conducted to develop a baseline for future studies.