Study Of Base Isolation Systems Under Vertical Earthquake Considering Inerters

Earthquake is one of most destructive disaster in nature.Most damages caused byearthquakes relate to the horizontal component of them,but the increasing amount of facts and studies show the vertical component will also be destructive.Under vertical earthquakes,some components of the vertical support system of structure will be in tension state and that will weaken ability of the shear resistant.Or the component will suffer from excessive axial force and crush,which will increase the instability of structures.The vertical andthree-dimensional isolation systems can control the structural responses well.However,those systems achieve good control effect by reducing the vertical stiffness of the isolation layer.The reduction will lead several problems:large vertical static displacement,concentration of displacement in the isolation layer,high possibility of the crash between the structure andbase and high possibility of the damages of the non-structural components.Besides,it will also lead to large rocking displacement under horizontal excitation and big challenges when repairing or replacing the instruments.Therefore,to study a novel vertical ormulti-dimensional isolation system has important values in engineering.Base on thechallenges the conventional isolation systems are facing with,this study will take advantage of the increasement of the dynamic mass that the inerter brings with to control the structural responses.The main contents and results of this study are:?1?This study analyzed the effect of inerter in the one-layer structure.In details,theinerter and clutching inerter damper were applied in vertical direction to control the structural responses of a one-layer but three degree-of-freedom?DOF?structure,including thehorizontal,rocking,and vertical DOF.And analyses of the structural mode,transfer function,H₂ norm and time history analysis were conducted.Results show that those inerters affect lightly on the horizontal response of the center of the mass.However,they control well on the vertical responses,and more importantly,the rocking responses,which balance the responses of different parts of the structure.?2?This study analyzed the effect of inerter in the multi-layer structure.In details,the inerter and clutching inerter damper were applied in the isolation layer to control the vertical structural responses.And the study also analyzed the relationship between the inertance and the stiffness of isolation layer,the variation of the structural mode,transfer function andH₂norm under different sets of inertance and vertical stiffness.Results show that the inerter and clutching inerter damper can control the structure well in the situation of relatively highvertical stiffness.And those instruments control effectively on the responses of the isolation layer,including displacement and acceleration responses;and have a similar control effect on the upper layers compared with the conventional isolation system.?3?This study analyzed the effect of inclined inerter in multi-dimensional isolation.In details,the inclined inerter and clutching inerter damper were applied in the one-layerstructure to control both horizontal and vertical responses.And the study also analyzed the influence of inclined inerter on the structure mode,and the variation of the transfer function of the horizontal-vertical-coupling system.Besides,the study conducted the optimal design of the inclination under different site condition and analyzed the effectiveness of the novelsystems under unidirectional excitation.Results show that,the inclined inerter affects on the structure non-linearly by the inclination angle,and can prolong the structural periods just like the inerter set unidirectionally.Then,the inclination angle is in some range making the inerter controls the acceleration responses of both direction well,and the effectiveness of the inerter is better than equivalent conventional isolation system in average,especially for thedisplacement responses.