Thesis or Dissertation Seismic performance of curved highway bridges with steel bearings under serious earthquakes

田, 欽

As urban areas have become more congested and highway interchanges have becomemore complex, horizontally curved composite steel I girder bridges have become an essentialcomponent in highway infrastructure. These types of bridges are key to providing smoothtransitions from one highway to the next, allowing for a seamless flow of traffic.Unfortunately, bridges with curved configurations may sustain severe damage owing torotation of the superstructure or displacement towards the outside of the curve due to thecomplex vibrations that occur during serious earthquakes. So how to improve the seismicbehavior of curved viaduct becomes important during strong earthquakes. Stopper installed atboth sides of roller bearing in tangential direction, cable restrainer equipped between adjacentsuperstructures, viscous damper installed at expansion joint and shock absorber device setbetween roller bearing and stopper are all evaluated respectively in this thesis.Traditional steel bearings are very common, but they are easy to be broken in earthquakes.Recently roller bearings equipped with stopper are installed on top of piers. Because stoppercan be easily installed and the price is not expensive, so it has wide application prospect infuture. Therefore, the effect of stopper together with cable restrainer on mitigating curvedviaduct damage during serious earthquake is carried out. The relationship between differentstopper values and the different types of damages is obtained. The advice for the seismicdesign of viaduct based on the appropriate stopper values has been put forward.Recently, cable restrainer installed at curved viaduct can significantly reduce thepossibility of deck unseating damage. In this thesis, the effect of stiffness and slack value ofcable restrainer on curved viaduct damage is presented. According to the evaluation results,the seismic design of curved viaduct based on the cable restrainer with appropriate stiffnessand slack value can be put forward. In addition, a comparison between restrained andunrestrained curved viaduct is also presented. Finally, the use of cable restrainer reducingcurved viaduct damage is proved in this thesis.In addition, application of viscous dampers to viaducts has gained significant attention inrecent years. Due to its large resistance force and energy dissipation capacity, viscousdampers have wide application prospect. The most advantage of viscous dampers is that itshows no resistance forces under slow relative movements of segments results from thermalchanges, creep and shrinkage effects. It is only activated when earthquake happens. Therefore,this thesis analyzes the overall performance of highway viaducts with different kinds ofviscous dampers and different stopper values. Different kinds of viscous dampers havedifferent stiffness and different resistance forces. So the relationships between different kindsof viscous dampers, different stopper values, and curved viaduct damage have been foundrespectively. A comparison between curved viaducts equipped with viscous dampers andwithout viscous dampers is also carried out. The calculation results demonstrated that stoppervalue plays a more important role in piers damage than viscous damper.In recent years, the effects of shock absorber devices installed between adjacent viaductsegments on reducing pounding forces, have been studied by many researchers. But theeffectiveness of shock absorber devices installed between roller bearing and stopper onreducing pounding damage, is lack. In this thesis, calculation results clearly show that thecurved viaduct with shock absorber devices between roller bearing and stopper present lessdamage. In addition, the effect of stiffness and thickness of shock absorber devices onmitigating curved viaduct damage is evaluated respectively. Besides, strain hardening, strainsoftening and elastic shock absorber devices are also analyzed in this thesis. Conclusively,shock absorber devices with large stiffness and large thickness present less viaduct damage.Curved viaduct with strain softening shock absorber devices exhibits less viaduct damage.
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Hokkaido University(北海道大学). 博士(工学)

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