Abstract
After the 1995 Kobe strong earthquake, it has been greatly revised in Japanese highway bridge codes. It was secured a large gap size of the girder for the collision of girders by the Level 2 Earthquake Ground Motion of the seismic design. However, if a large gap size of the girder is adopted, the expansion joint have to be largely changed. Furthermore, the construction costs and the seismic reinforcement costs will be increased. It was considered that the gap reduction allowing the collision of girders, as a premise of preventing the collapse of the bridge, was one of the seismic reinforcement method in order to decease the construction costs and the seismic reinforcement costs. In addition, it is necessary that damage of the girder end and the pier bottom is decreased by attaching rubber shock absorber to the end of girder. In order to reduce gap size between girders, it is necessary that the resistance characteristics of the abutment due to the collision of girders and the dynamic response characteristics due to the damping at the bottom of pier are grasped. Although many studies on the collision phenomenon of bridge girders have been published, the effects of cost on seismic reinforcement allowing the collision of PC bridge girders have not been sufficiently considered yet. In this study, the resistance characteristics of the abutment due to the collision of girders and the dynamic response characteristics due to the damping at the bottom of pier will be verified by carrying out dynamic response analysis that the 3-dimensional finite element model (3D-FEM) of the PC bridge was built. In addition, the effects of cost on the proposed seismic reinforcement allowing the collision of concrete bridge girders will be considered. From the comparison of the total cost on both the current method and the proposed one, it will be confirmed that the proposed seismic reinforcement method is very effective.
Highlights
A large number of bridges were damaged during unexpectedly severe earthquakes, such as 1995 Kobe strong earthquake and 2011 Tohoku strong earthquake
It was found that the dominant natural frequency for Model-2 installed the seismic isolation rubber at the base of P1 pier was reduced by 59 %
The validity of the seismic isolation rubber was recognized. Based on these analytical results, it was found that there is a possibility of controlling of the allowance a certain amount of girder collision and a slight damage of the abutment and the pier bottom by using a girder bridge which consists the pier with seismic isolation rubber and the girder with the gap size 20 cm
Summary
A large number of bridges were damaged during unexpectedly severe earthquakes, such as 1995 Kobe strong earthquake and 2011 Tohoku strong earthquake. It has been suggested that allowing the girder collision at the abutment by restricting the girder bridges displacement, the size of expansion joints can be reduced These conditions are able to reduce the seismic design and seismic reinforcement cost. As one measure to reduce the seismic response without changing the existing bearing conditions, the effectiveness of the seismic response reduction method by seismic isolation of the pier bottom was examined in addition to the girder collision. According to this analysis, it was found that the effectiveness of the hybrid reduction method of the seismic response can be confirmed depending on the input earthquake motion by considering the beam end collision and the seismic isolation pier. Tomohisa Hamamoto et al.: Analytical Study on Seismic Response Reduction for PC Bridge: Effects of
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