Comparison Of Seismic Design Schemes For Long-span Concrete Continuous Highway Girder Bridges

Long-span concrete continuous girder bridge normally has heavy concrete girder with several bridge units, the type of the structures are usually rigid. Therefore the original seismic design with one fixed bearing and pier is difficult when earthquake comes. The new type of seismic device and isolation technology is less in use in our country, so the seismic technology is quite necessary to be integrated and analyzed for improving the seismic level of long-span continuous girder bridges.The seismic design methods and the development of seismic isolation technology are detailed in this paper, seven seismic designs schemes are investigated combined with a five span concrete continuous girder bridge. Seismic design with single fixed bearing, double fixed bearing, lock-up device and the functional bearing system, isolation seismic design with LRB bearing, FPS bearing and SMA bearing are comparatively analyzed. The main study contents and results of this paper are presented as follows:(1) The finite element simulation for different part of the continuous bridges and the corresponding seismic analyze methods are summarized. Two-dimensional finite element model of background bridge is built by the computer program MIDAS/Civil.(2) Effectiveness of the four seismic design schemes is analyzed. Operating principle, placement effect and pier height effect are discussed. The result shows that the inner force of fixed pier can be improved by Lock-up device under earthquake, however the stiffness of the structure is increased. The Lock-up device is more suitable for continuous bridges with high piers.(3)The theory conception, mechanical model and design process of functional bearing system are summarized. Functional bearing is a system that use frictional sliding to do the isolation and elastic-plastic hysteresis curve to stimulate the mechanical model.(4)The basic construction, mechanical model and working principle of three isolation designs are discussed, the effectiveness, placement effect, key parameter and pier height effect of the isolation seismic designs were analyzed. The results shows all devices can play effective roles in isolation, FPS is the best in extending structure period, SMA is the best in reducing the seismic action of substructure.(5)Seven seismic designs scheme with the typical parameters is picked, the seismic performance, economical efficiency and construction convenience are compared, in order to get the optimal seismic design for long-span concrete continuous girder bridge. The comparison and results show that the functional bearing system is the most suitable plan for seismic design of continuous bridges.