Research On Torsional Vibration Of Friction Pendulum System To Bi-directional Horizontal Earthquake

In recent years, Friction Pendulum System technology gradually has emerged as anew thinking of all seismic friction isolation technologies, based on a great manyliteratures on the study of the seismic friction isolation. However, the structure isusually simplified in those previous studies as a single particle system or a multitudeparticle system in the interest of calculation and designing when designing thebase-isolated structure. The assumption of the calculation is that the structure performshorizontal displacement and no torsional displacement. But with the diversification andcomplication of tall building structures, structure performs coupling torsional responsesbesides horizontal movement under bi-directional horizontal earthquake ground motionbecause the quality center does not coincide with the stiffness center and that leads todiscontinuity of the building structures. Therefore, a study about responses of torsionalvibration of Friction Pendulum System to bi-directional horizontal earthquake groundmotion is of great significance.In this thesis, Friction Pendulum System to bi-directional horizontal earthquake areexamined in the following three aspects:First, the basic principles of torsional vibration in building structures are studied inthis thesis. The primary causes and control methods of torsional destruction in buildingstructures are elaborated. It shows that the irregular structures highly prone todestruction by torsion. In this case, torsional displacement ratio and torsional periodratio are deemed two control indexes of resisting torsional vibration destruction.Second, the seismic reduction behavior of torsional vibration of Friction PendulumSystem is analyzed. The model of series-wound rigid body system is adopted as thedynamic analysis for bi-directional horizontal earthquake ground motion, and dynamical equation of the structure performing coupling torsional responses isestablished. The time-history analysis for a six-storey reinforced concrete framebuilding on lateral-torsional coupled seismic response of the friction isolation structureand base-fixed structure is carried out. It shows that the Friction Pendulum System isvery effective in reducing structure seismic response under bi-directional horizontalearthquake ground motion. Besides, it can also reduce the response of torsionalvibration under bi-directional horizontal earthquake ground motion. Therefore, it canimprove the stability of series-wound rigid body system and avoid the destroying oftorsional vibration, and thus ensures the security of the structures.Third, the responses of torsional vibration of the spreading layer upon layer arediscussed. The results show that torsional period ratio on responses of torsionalvibration and the specified measures for control index need to be revisited. The primarycauses of torsional period ratio exceeding, the limit value are analyzed throughtheoretical reasoning. It shows that the torsional period ratio cannot guarantee responsesof torsional vibration in certain situations, as in the case of the spreading layer uponlayer. It is concluded accordingly that the limitation of the period ratio in current codecan be cancelled in some situations. According to that, the ratio of lateral energy totorsional energy is proposed as an alternative.