Study On The Influence Of Seismic Performance Caused By Design Parameters Of Extradosed Bridge

China is an earthquake-prone country,seismic research of structure has been a hotspot in the field of engineering structure.Because bridges as an important structure occupied a special position in the infrastructure,its seismic performance has always been paid attention to from engineering and academia.The extradosed bridge has been used widely after development of nearly 20 years,but its seismic performance remains to be studied further.This paper analyzed influence of seismic performance because of parameters variation of extradosed bridge from the aspect of structural design and investigated dynamic time-history response of structures in different seismic directions by selecting three design parameters that includes single-double pier,connection between pier and beam,ratio between pier height and middle span.The main contents and conclusions are introduced as follows:(1)Reviewed the origin and development of extradosed bridge and made a sketch about research status at home and abroad.(2)Prepared for subsequent calculation and analysis by introducing relevant design parameters,expounding all kinds of theory of seismic response analysis systematically and mainly introducing IDA analysis method used in this paper.(3)After introducing principle of establishing model and restoring force model of steel reinforced concrete,elastic plastic dynamic analysis model of Xijiang Bridge is established by using MIDAS/CIVIL which considers the plastic hinge.Through analyzed vibration character of model,corresponding cycles and frequencies of the first 30 modes was acquired which is providing relevant data for IDA analysis.(4)The IDA analysis of the model achieved by modifying the above benchmark model under the different design parameters such as single-double pier,connection between pier and beam,ratio between pier height and middle span.The calculated seismic response was sorted into the IDA curve and analyzing influence of seismic performance because of parameters variation based on curve.Comparing the results of different models,we found that the single and double piers show great differences on deformation and bending moment under different seismic directions,these differences were also found in other study of design parameters.Seismic response of piers increased in longitudinal direction but reduced in cross bridge direction after changing the connection between pier and beam to elastic connection.The reduce of ratio between pier height and middle span was beneficial under two directions earthquake,which the benefit was more obvious in single pie.Seismic response of piers increased under two directions earthquake increased after magnifying the ratio between pier height and middle span,which the increasing was more obvious in single pie under longitudinal earthquake.The law of analysis could provide reference for seismic design of the same type bridge in the future.