Keywords: abutment of a bridge, damper, highway bridge, simulation, earthquake, seismic design.

Various types of damper are now practically used for seismic isolation and structural control. However they are still quite limited in application to bridge systems. Kawashima et al. [1] studied the reduction effect of collision forces and variations of the response characteristics when a rubber buffer is installed in girders for eliminating collision. Unjo et al. [2] installed a buffer between the girder and the abutment for a bridge with elastic bearings and analytically studied the reduction effect of the buffer. On the other hand, Otsuka et al. [3] studied enforcement measures to improve the seismic performance of existing bridges by introducing a seismic isolation bearing. Nishioka et al. [4] analytically examined the effect of displacement control considering the natural period, the equivalent mass and the expansion gap in a bridge with an abutment at both ends. Ogura et al. [5] taking up bridges installed with rubber bearings, analytically studied the response characteristics and the seismic performance of the whole bridge system when girders collide with a parapet wall of the abutment in a large earthquake.

In this study, four spans of a continuous steel girder bridge were selected as a structure for examination. Originally this model was prepared for examination of the seismic reinforcement considering seismic isolation. In this examination, a damper is installed in the abutment of a bridge part at both ends. The seismic isolation bearing is changed to an elastic bearing. The whole bridge system was modelled as a plane framed model. A natural rubber bearing was assumed to distribute the reaction force. The reaction force distribution bearing was modelled as an elastic spring. The spring constant was so that the target natural period of the superstructure might be satisfied. The mass was distributed to the abutment of the bridge and the bridge pier. In this examination, the elastic spring and reaction force distribution bearing were set up so that the target natural period might be set to 2 sec, 3 sec, and 4 sec to the mass of a superstructure. A dynamic response analysis of a bridge with the dampers on its abutment has been conducted. The basic characteristics of a bridge system with a damper settled on the bridge abutment were evaluated. The seismic coefficient to the yield load of a damper, the maximum acceleration of the superstructure and the reaction force induced at the bridge abutment were confirmed as the characteristics of the damper. Damper performance has been assessed with a view to securing a rational seismic safety of the bridge system.

1

K. Kawashima, M. Shoji, "Effectiveness of rubber type restrainer to mitigate pounding effect between adjacent decks during a strong earthquake", Journal of infrastructure planning and management, No.612/I-46, 129-142, 1999.

2

S. Unjou, M. Kondou, S. Mikami, "Influence that collision of edge of superstructure and abutment exerts on behaviour at earthquake in the entire bridge (design method feature)", Civil Engineering Journal, 44-2, 20-25, 2002.

3

H. Otuka, T. Tanaka, K. Aikyo, T. Soma, "Seismic isolation system of existing continuous box girder bridges and countermeasures for seismic safety with stiffness of the abutments and back fill", Bridge and foundation engineering, Vol. 35, No. 10, 33-39, 2001.

4

T. Nishioka, S. Unjou, "Research about seismic action of existing continuous box Girder bridges had abutment at either end of the bridge", symposium journals about earthquake-proof brace of existing structure, 23-30,2002.

5

Y. Ogura, S. Unjou, "Characteristics abutment of a bridge's had beam's collision earthquake time", Society of civil engineers association for earthquake engineering journals, Society of Civil Engineers, Vol.27, 2003.

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