INFLUENCE OF NEAR-FIELD VERTICAL GROUND MOTIONS ON THE SEISMIC RESPONSE OF LRB BASE-ISOLATED STRUCTURES

This paper mainly concerns the influence of near-field vertical ground motions on the seismic response of base-isolated structures equipped with lead rubber bearings. Firstly, a relatively precise finite-element model was presented in ABAQUS finite element software. The fiber model was adopted to simulate the superstructure as plastic deformation may occur under the near-field ground motion, and the "Ryan-Kelly" mechanical model was introduced into the software as a user-defined element to consider the coupling effects between the horizontal and vertical mechanical behavior of the bearings. Moreover, to analyze the influence of near-field vertical ground motion on the failure mode of the bearings, a failure boundary was determined by comprehensively considering the maximum horizontal displacement, the buckling limit under pressure and the maximum tensile stress of the bearings. A comparative study based on the model was conducted to analyze the influence of near-field vertical ground motions on the seismic response of base-isolated structures. The results show that the vertical ground motion significantly affects the failure mode of the bearings and may cause the bearings to buckle under pressure or to be damaged under tension before they exceed the horizontal displacement limit. The results also show that in some cases, the seismic response of the superstructure is reduced when the vertical ground motion is taken into consideration.