Abstract
A bridge unseating prevention system is a safety system for bridge collapses caused by large earthquakes, beyond the assumption of aseismic design specifications. Presently, the system is generally adopted for newly constructed bridges and the seismic retrofitting of existing bridges. Cable type bridge restrainers are included in the system, and they are expected to prevent superstructures from exceeding the seat length of substructures. Although the bridge restrainer works during an earthquake, it is designed to be static in the current design. In addition, although the constituent elements of bridge restrainers include a rubber cushion to absorb energy during an earthquake, the effect is not included in the design. Thus, the current design lacks the dynamic effects of earthquakes and the cushioning effect of the rubber. Furthermore, in the case of a multi-span bridge, there is no particular decision as to where the restrainers should be placed or what kind of specifications they should have. Therefore, in this paper, a new design concept that considers the dynamic action of the earthquake and the cushioning effect of the rubber is proposed by coupling dynamic response analysis using a frame finite element (FE) model and a simple genetic algorithm (SGA).
Highlights
In order to prevent damage to bridge structures by seismic excitation, various types of countermeasures to bridge collapses are adopted in earthquake-prone regions
The results of the seismic response analysis, which was conducted to confirm the working condition of the bridge restrainer, show that the bridge restrainer did not work when assuming the breaking of all fixed supports
There is a risk of bridge collapse when the bridge restrainer is installed between girders, even though the relative displacement between the superstructure and substructure does not reach the working gap of the bridge restrainer
Summary
In order to prevent damage to bridge structures by seismic excitation, various types of countermeasures to bridge collapses are adopted in earthquake-prone regions. The bridge unseating prevention system (Figure 1) is well defined, specifies the girder seating length and requires bridge restrainers and lateral displacement constraint structures to be installed on bridges, according to the Japanese seismic design specifications for highway bridges [2]. The function of this system is to prevent superstructures from being displaced from substructures because of massive earthquakes beyond the assumptions of aseismic design specifications.
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