Study On Seismic Behavior Of Continuous Rigid-frame Bridge With High Piers

Holding the development trend of higher piers and longer span in China,the continuous rigid-frame bridge has won the appreciation in the bridgeconstruction field by outstanding crossing ability, smooth driving condition andmore convenient construction methods itself. The Great Wenchuan Earthquakebrought an unprecedented shock to the traffic lines in western China, the veryonly continuous rigid-frame bridge in the meizoseismal area demonstrated adifferent damaged form from the traditional girder bridge. Considering a shortconstruction history and little seismic experience, such kind of bridge urgentlycalls for the relational seismic research in our earthquake-prone country.Through the structural study, seismic hazard delving，pseudo-dynamicexperiment and structural simulation analysis, the seismic performance of cont-inuous rigid-frame bridges with high piers was studied. The main work and se-veral understanding are stated as following:1. It is considered that the thin-walled beam theory is suitable for the anal-ysis of the thin-walled pier under lateral earthquake load, structural propertyanalysis and four specifically described results of bridge seismic experimentssuggest that stress at the bottom of the thin-walled pier subjected to lateral loadon the top of the pier presents uneven distribution with a lager stress and moreremarkable failure in the corner of the pier than that in the middle side.2. The earthquake damage of Miaoziping bridge was delved. It is revealedthat the tip of side span girder is the seismic weakness part under earthquakewith the squeeze damage of bearings and the impact damage of girder end andblocks which were caused by huge transverse seismic displacement of girderend. It is conjectured that the longitudinal projection form of composite displa-cement revealed as a shell via the seismic damage of bearings and blocks.3. Based on modal test of one typical continuous rigid-frame bridge withhigh piers—Niulanjiang bridge, a1:12scale model was designed to performethe pseudo-dynamic test on its seismic weakness direction.The experiementresults that the specimen designed by1:1acceleration scale achieved only hor-izontal ring cracks at the bottom of the pier subjected to input ground motionof PGA=1.5g but neither spall of concrete nor reinforcement yielding and thepeak strain of longitudinal reinforcements was less than its ultimate strain showed such kind of bridge possessed extraordinary seismic ability.4. Based on design documentation of the very bridge above, the seismicresponse analysis was run under computing platform of the general finite elem-ent(Midas/Civil). The simulation analysis showed that the side span of girderachieved magnificently greater transverse displacement response than that onthe top of the traction pier with the magnification corresponding to the peakgroud acceleration and the frequency components of the input ground motion,the longitudinal projection form of spatial girder movement was similar to ashell.The stress distribution of the steel fiber at the bottom of the pier insistedthe trend that the stress in the corner reminded lager than that in the middle,and the strain-stress curve of the steels at the bottom of the pier acted a plastichysteretic feature of ductility column under the input of strong ground motionsimutanouesly.