Earthquake Control Of Space Asymmetric Frame Structure

At present, in practical design and construction of project, there exist lots ofasymmetric buildings due to the limitation of site and requlrement of using functionand building configuration. The experiences indicate, the damage of asymmetricsmicture subected to earthquake motion is severe, Which may be thebuted to theeccentric torsional effect. In recen years, the involved literatures note that adoptingthe base-isolated technique to control torsional vibration is one of alterative methodsto tackle this kind of problem. However the detailed research achievement controllingtorsion vibraion is scarce, and it has been yet an outstanding problem in buildingengmeermg.In this paper firstly in terms of the character of spatial asymmetric RC framestruture and the requirement of controlling torsion vibration, a 3-D member-storymodel is established with taking the Bearing and Lead the Bearing asisolators. Based on the hypothesis of floor rigid membrane to concern the spatialrestraint of floor panel, the static condensation technique is employed in the model.Therefore, through adopting the model, the DOF of dynamic system is reduced, andthe shortcoming of algorithm instability of member model is overcome. Furthermore,the numerical accuracy is improved. Because of these advantages the 3-D memberstory model is a calculating model feasible widely for linear and nonlinear seismicanalysis of space frame structure.Based on the model mentioned above, the author develops a 3-D linear andnonlinear dynamic time-history analysis program of frame Structure under the multi-dimension ground motions considering the directional relationShip of restoring forcemodel of noulinear seismic isolation bearing. Secondly, two typical multistoryasymmetric RC for Structures with the pratical engineering background subjectedto unidirectional and bi-directional El Centro and Taft or San Fernado earthquakewaves are served as studying object, adopting conventional fixed-base and RB orLRB base-isolated methods respechvely Then, series of translation-torsion couplingseismic responses are analyzed comparatively.The calculated results show making use of the base-isolated technique, theeccentric torsion effect of multistory asymmetric frame structure can be controlledeffectively and conveniently under not only unidirectional but also bi-directionalearthquak excitations.The oPtimal disposihon of seisndc isolation devices is also discussed in this paPerThrough adjuSting the thess Center Of isolators to aPPrach the pec masswt of suPersghCtUre, the torson reopase of suPerStrUCtUr is reduced sighficantiy,Whch attains the desi~ god of OPtimal mitgatin disasters.Finally, as COmpe the halation-tOrsion couPling seismic reSPonse ofaSycoetric boe eq subjected to bi-ditectional with unidirectional earthqUakeW the rech lilusha, the aseisInic caPacity of StrUCtUr in the case of bi-directiond earthqUake is worse. It accords with the conclusion tha Code for seismicdesign Of building (ReVision Version, China) emPhasizes. Tha is the torsion effectunder bi-directional wtpe action on the struCtUre with remarkabIy uneven andasynunetric diStribution Of mass and stiffeess should be considered.