Development of sliding bearing system for multi-level earthquake motions

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The aim of this study is to develop the sliding bearing system for bridges to meet the multi-level earthquakes. The integrated sliding bearing system utilizes rubber bearing plates to support the main loads, such as dead loads and live loads, and a slider-buffer system to reduce seismic response by frictional damping.It is almost impossible for any single bearing device to satisfy the functional requirements for both everyday general use and the reduction of the seismic response. Furthermore, the strength range of the earthquake motions is very wide to meet for a single device. However, it might be possible to combine one device that has everyday functionality with devices designed to meet the various range of the seismic responses.A multi-level buffer utilizes two different types of buffer in tandem. The stoppers between the two buffers would break under loads greater than Level-1 earthquakes. During Level-1 earthquakes, the displacement response would be limited not to collide with adjacent girders. In this case, the device functions as a joint protector. During Level-2 earthquakes, the stopper would break, enabling the girder to vibrate with large excursion in long natural period. This would result in large amounts of energy being absorbed by friction at the sliding interface of the bearings.The destruction probability of the stoppers was taken into account in the numerical simulations. The results showed that the variation in the strength of the stoppers did not affect the response of the whole bridge system. In this way, new systems developed from the current system would expand the application of integrated sliding bearings.