Study On The Computation Method For The Seismic Analysis And Control Of The Multi-spanned Continuous Type Bridge

A large number of seismic investigations have shown that the damages for the continuous system typed bridge are very serious.As a result,In order to protect continuous system typed bridge from seismic damages,it is very important to study the seismic resistance design and analysis method and seismic control method for continuous system typed bridge.Nowadays,with the great efforts put by the bridge seismic researchers,a large steps have been made in the bridge seismic resistance study.For example,performance based bridge seismic ductility design idea has been adopted as the core by the Chinese highway bridge seismic design criteria published in 2008.And another resistance idea,seismic isolation,is applied widely on a large number of lately constructed large span bridges in China.Besides,a new strategy,seismic active control,which is based on the feedback control theory,are now under study and development by some researchers,and so far,this technology appears only on a few of large spanned cable stayed or suspensioned bridges.To apply the latter on the continuous system bridges,in this thesis,the author firstly conducted some studies on soil-pile dynamic interaction,the bridge seismic isolation analysis and design and the seismic resistance ductility design,using the spectrum response method,nonlinear time history analysis method and the nonlinear pushover method respectively based on three different continuous system bridges.Then based on a typical 4×50m continuous system bridge,the applicability of two active control schemes and one hybrid control scheme will be checked on this bridge.Upon all the studies conducted in this thesis,the following achievements and results can be summarized as below:1.Firstly,three different traditional seismic resistance analysis methods for the multispanned continuous system typed bridge are studied.Based on the linear seismic spectrum analysis,one novelty approach in considering the soil-structure dynamic interaction is proposed and is illustrated successfully further with one 6×75m reinforced concrete and steel composite bridge of one cross sea bridge project.Then Based on the nonlinear time history analysis method,and illustrated by a 6×110m continuous steel girder bridge of one cross sea bridge project,an extensive study is conducted on the behavior of seismically isolated continuous bridges,of which transverse and longitudinal seismic input are considered simultaneously.Finally,based on the ATC-40 Nonlinear Pushover method,with an overhead viaduct bridge project,an in-depth ductility seismic design is conducted in detail for each primary element using Sap2000 BRIDGE.2.Based on the above mentioned studies,the emphasis will be put on the active and hybrid seismic control study for one typical 4x50 m continuous system bridge.Since so far there is no any commercial software could be used to conduct active and hybrid seismic control study for the continuous system typed bridge,a MATLAB&SIMULINK 3D nonlinear program NLBA1.0 is coded by the author,considering Matlab's powerful function in control domain,NLBA1.0 based bridge model could be effectively used for the seismic control study.Besides,NLBA1.0 could be used for the complex modal analysis and the mass,stiffness and damping matrix output.Based on NLBA1.0,a 3D frame finite-element model for a 4x50 m continuous(rigid frame)bridge is developed,and the modal analysis is conducted and the results is compared with that of the corresponding Sap2000 model,so that the validity of the NLBA1.0 linear bridge model is finally verified.3.In order to assure the reliability of the active and hybrid seismic control studies for the continuous system bridge,NLBA1.0 is capable of modeling both the nonlinear plastic hinge with the moment-axial force yielding interaction being considered,and the seismic base isolator.Besides,8 indexes in evaluating the seismic damages of the bridge are specified in NLBA1.0 so that the performance of the ductility design,the base isolation and the active or hybrid control strategies could be compared.The coupled differential equations could be solved using the direct nonlinear time history method by NLBA1.0,and in this way,the control force could be placed easily in the bridge model.Besides,8 indexes in evaluating the seismic damages of the bridge pier are specified in NLBA1.0 so that the performance of the ductility design,the base isolation and the active or hybrid control strategies could be compared.Based on the functions mentioned above,using NLBA1.0,a nonlinear finite-element model for the 4x50 m continuous(rigid frame)bridge is developed with the nonlinearities of the piers and base isolators being considered.One nonlinear time history analysis is performed and compared with that of the corresponding Sap2000 nonlinear bridge model,and finally the validity of the NLBA1.0 nonlinear bridge model isverified.4.A MATLAB&SIMULINK platform NLAHC1.0 is established for the first time by author to conduct the seismic active and hybrid control for the continuous system typed bridge.Through the interface coded in NLAHC1.0,NLBA1.0 nonlinear bridge model could be introduced into the platform,therefore,NLAHC1.0 is able to perform accurate control simulation in considering nonlinearities from the pier hinge and base isolator.Besides,NLAHC1.0 is able to easily and accurately simulate the different sensors and actuators alignment,transverse and longitudinal actuator force could be exerted simultaneously by NLAHC1.0 either.Apart from those mentioned above,one Kalman filter acts for the first time as the seismic observer to estimate the bridge seismic response in NLAHC1.0,and an eigenmode reduction method in NLAHC1.0 is for the first time being introducded to reduce the sizes of the evaluation model and speed the control process so that the static and dynamic characteristics of the original evaluation model could be kept as intended.Of the most importance,based on the functions listed above,NLAHC1.0 is capable of manipulating the LQG(Linear Quadratic Gaussian)controller to conduct a variety of acvie and hybrid seismic control schemes with different type of seismic input.5.Finally using NLBA1.0 and NLAHC1.0,three active or hybrid LQG control schemes are taken into account in conducting the bridge nonlinear seismic response analysis respectively for the 4x50 m continuous system bridge.Through the comparisions among the study results,the optimal scheme is found to be used as the best choice for the multispanned continuous type of bridge.