Effect of Different Constraint Systems on the Seismic Response of Double-Deck Curved Girder Bridges

Double-deck curved girder bridges can achieve large climb in a short distance, and their seismic response differs from that of regular bridges due to their special structural form. The constraint system of bridges, which consists of bearings and shear keys, has a key influence on the seismic response of the bridge structure. Accordingly, this research aims to develop a reasonable constraint system for double-deck curved girder bridges. A finite element simulation of a double-layer curved steel box girder bridge is also conducted to compare some indexes, which are the displacement of bearings with the curvature of the pier section. The shear bolt is selected as the limit device to study the influence of shear bolts and different bearings on the seismic response of the double-deck curved girder bridge structure. Under the influence of ground motion, the displacement of the upper bearings of double-layer curved girder bridges is generally larger than that of the lower bearings. The double-layer constraint system makes the section curvature and ductility in the middle of the pier smaller than that at the top and bottom of the pier. The spherical steel bearings have a small displacement, whereas the pier has a large internal force. After setting the shear bolts, the displacement of the spherical steel bearings decreases, whereas the damage to bridge piers does not show obvious changes. When the displacement of elastomeric pad bearings increases, sliding occurs under a low ground motion intensity, thereby reducing the degree of damage to the bridge pier. Moreover, the application of shear bolts limits the displacement of bearings and subsequently increases the seismic force being transmitted to the pier whose damage is the most serious. However, the displacement of pot bearings is relatively small, and the displacements of the upper and lower layers are close. In addition, the seismic inertial force of the superstructure is relatively uniform, thereby protecting the piers to a certain extent. After setting the shear bolts, the deformation falls within an allowable range, whereas the damage to the bridge piers slightly increases. Therefore, combining pot bearings with shear bolts creates a reasonable constraint system for double-deck curved girder bridges.