| Viaducts play an important role in modern highway transportation and citytransportation, and continuous girder bridges shares a high proportion, but the multi-point seismic response of them has been seldom taken into consideration. Some newaseismatic design principles of viaducts should be abtained according to the largequantity and various destructional forms of destroyed viaducts during Wenchuanearthquake, while the effect of seismic response under spatial earthquakes excitationsis not ruled in detail. On the other hand, the improved energy-dissipation technologyis more and more used in large-span bridges, while there is few study and applicationof the technology on the continuous viaducts. Therefore, this paper takes the two-column pier continuous girder bridge, the common type of viaducts, as the majorobject of study, and conducts some research in multi-point seismic response andenergy-dissipation theory. The main research and conclutions are as follows.1. The dynamic equations, separately based on the Base Absolute DisplacementMethod (BADM), relative motion method (RMM) and large mass method (LMM) arededuced. As a matter of fact, the ultimate equations of BADM and LMM are mainlythe same ones. The effects of additional base mass and damping ratio on the LMMprecision are discussed in use of SAP2000, and it is recommended that the additionalbase mass can be set the104times of base reaction force and the damping ratio affectsa little the LMM precision. Meanwhile, the damping ratio can affects a little on theBADM. The FE model of typical viaduct is established and the effects of the multi-point seismic response is analyzed considering some factors, including span, spannumber, pier height, travelling wave velocity, coherency and local site effect. Somequalitative conclusions are obtained.2. The calculation module of the pounding models in common, including linearmodel, Kelvin model, Hertz model and Hertz-damp model, are developed based onANSYS. The effects on the seismic response on of pounding is analyzed, and it isclearly can be deduced that the pounding can lead to the bearings' damage andaggravate the plastic hinge damage near the bottom of pier. The seismic response ofviaduct under multi-point and near-fault earthquake excitations are calculated, whichconfirms that the multi-point and near-fault earthquake excitations can severelyenlarge the pounding force and response. A type of damper, Metal Alloy Brace (MAB),which possesses the characteristics of two stages of damping force, is recommendedto reduce even remove the pounding force and decrease the dynamic response of theviaduct. However, the seismic control of pounding response is more superior undernear-fault earthquake inputs.3. A1:10scaled bridge model of a typical viaduct designed and manufactured, andthe model bridge is placed on the shaking table array. The dynamic characteristic parameters are identified according to the artificial excitations and white noiseexcitations, and compared with the calculation value of FE model, which reveals thatthe parameters values match each other perfectly. Furthermore, it is verified that abilinear model should be used to simulate the traverse rigidity of the sliding bearings.4. The shaking table tests of the scaled viaduct are conduct under differentearthquake excitations. Four artificial earthquake records witch fitted the designedfour site types and four earthquake records which accord with the four site types areused to be as the one dimensional and two dimensional uniform excitations, whichreveal the impact on the viaduct's seismic response of site factor. It is confirmed thatthere is a great deal of difference of the viaduct under different earthquake excitationsaccording to different sites. Besides two earthquake records and one artificialearthquake record are chosen to conduct the one dimensional travelling waveexcitations considering different travelling velocity, and the results are compared withthe seismic response under uniform excitations. At last, the artificial earthquakerecords which considering the incoherence effect and local site effect are generated toconduct the one dimensional shaking table tests to explore the seismic response ofviaducts under multi-point earthquake excitations.5. Four viscous dampers are designed and manufactured, and the damping force-displacement curves and damping force-velocity curves are gained under differentfrequency sine excitations. It is demonstrated that the relationship between thedamping force and velocity is closed to linear under high frequency sine excitation.Further, the Maxwell model is suitable to simulate the viscous dampers, while thetested hysterrisis curve is plumper than the calculated curve. Fit the dampers betweenthe side piers and the girder, and the damping effect of the viscous dampers is testedunder longitudinal uniform and multi-point excitations. The test dynamic responsecomparison of the viaduct between with dampers and without dampers shows that theviscous dampers play a part in energy dissipation.6. The Incremental Dynamic Analysis (IDA) theory is introduced and the IDAanalysis of the viaduct is conducted under uniform excitations. Meanwhile thedamage measure and intensity measure indexes are discussed during the analysis. It isrecommended that the plastic hinge rotation, the bearing displacement and the bearingshear force all should be taken as the DM indexes and the traverse bearings' shearforce is not sufficient to resist the earthquake excitations. An artificial earthquakerecord is selected to conduct the IDA shaking table test and the tested results arecompared with the FE model analysis. The IDA is also conducted on the viaductunder the travelling wave excitations and multipoint excitations consideringcoherency and local site effect, and the results are also compared with the resultsunder uniform excitations. It is deduced that the distinction of the dynamic responseof the viaduct under multi-point dynamic response and uniform excitation of the viaduct changes along with the intensity of the earthquake excitations.
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