Seismic Response Analysis Study Of Three-dimensional Isolated Bridge Structure

Isolated bridge technique is an effective approach to improve seismic resistanceperformance of bridges which play a prominent role in the urban lifeline system.Theory analysis and experiment research are mainly performed in domestic andoverseas, but researches on multi-dimensional seismic action and three-dimensionalseismic isolation technique are seldom investigated. Isolated bridge technique havebeen extensively applied to practical project in overseas, but seldom in domestic. Anew bridge three-dimensional seismic isolator is proposed in this dissertation andcorrelative theory analysis and experiment research are carried out, its horizontal andvertical isolation effect is validated, influence of bearing parameters, multi-directionseismic action and height of pier on earthquake response of continuous bridges andseismic isolation effect of the isolator. The contents of this dissertation are mainly asfollows:(1) Many documents are consulted, in order to comprehend the basic principle ofisolation system and chief type and performance of isolated equipment, comprehendand predominate the developing history and research present state in domestic andoverseas of absorption of vibration and isolation technique of bridge, be familiar withthe research progress of three-dimensional isolation technique, finally giving theresearch content of this paper.(2) Dynamic response characteristics and analysis method of three-dimensionalseismic response of isolated bridge structure are studied. One side, the influencefactor of dynamic response characteristics are analyzed of isolated bridge, accordinglyeducing some significative conclusions; on the other hand, the analysis method ofthree-dimensional seismic response of isolated bridge structure is given, which areexact frequency-domain seismic response analysis and qualitative random seismicresponse analysis methods, at the same time introducing several seismic motionrandom modal in normal.(3) According to the principle of three-dimensional isolated technique, a thick-layerrubber isolator is designed, which has the ability of generate horizontal and verticaldeformation simultaneously. The thick-layer rubber isolator is the important elementof bridge three-dimensional isolator that giving in this paper. Study and analyze thestructure, mechanical property characteristics and calculated modal and method ofparameters of thick-layer rubber isolator, and systemic testing research conventionalrubber bearing and lead rubber bearing and new-type thick-layer rubber bearing. The conclusion is the horizontal and vertical mechanical characteristics of thick-layerrubber bearing satisfying the design condition of bridge three-dimensional isolatoraccording to the test data.(4) According to the principle of three-dimensional isolated technique and physicaland mechanical properties of lead, firstly, design a deformed lead damper which hashorizontal and vertical dissipative ability simultaneously, study and analyze thestructure, mechanical property characteristics and calculated modal and method ofparameters of all elements. Secondly, describe the test method and contend, inductand generalize the mechanical property characteristics of deformed damper accordingto analyze test data. Finally, educe some significative conclusions according to theoryand test analysis.(5) Artificial analyze a continuous beam bridge installed a three-dimensional isolator.A three-dimensional finite element modal of three-span continuous beam bridge isestablished on the base of rigid foundation assumption. Firstly, dynamic characteristi-cs of continuous beam bridge are analyzed. Then seismic response of the bridge iscalculated with dynamic time-history analysis method, validating horizontal andvertical seismic isolation effect, influence of factors such as parameters of isolator,multi-directional seismic action and height of pier on seismic isolation effect arestudied. Results show that the bridge three-dimensional isolator has favorablehorizontal and vertical isolation effect. Horizontal reduction efficiency will rise withthe increase of the ratio of pre-yield and post yield stiffness of the isolator. Theinfluence of multi-directional seismic action on isolated and non-isolated bridges areprominent. With the increase of height of pier, horizontal isolation effect will increasebut will be gently.The proposal of bridge three-dimensional isolator and its design method haveimportant developed meaning to vertical and three-dimensional isolation in China.Configuration of the isolator is simple, its capacity performance is reasonable and itscost is relatively low, it can be applied as three-dimensional isolator in engineeringstructures such as buildings and bridges, but also as vertical vibration isolation inlarge-scale mechanical equipments, possessing great practical future.