Influence of vertical ground motion on seismic responses of triple friction pendulum interlayer isolation structures

In order to investigate the influence of vertical ground motion on seismic responses of story-isolation structures mounted on triple friction pendulum (TFP) bearings, the finite element model of a six-story building with various types of interlayer isolation TFP bearings under far field or near fault ground motions is established and analysed. A discrepancy rate function of peak interlayer shear, acceleration and displacement results is adopted to discuss the influence of the vertical seismic motions on isolation structural responses. Furthermore, the isolation form, the isolation period and the friction coefficient of bearings are changed to study their effect on the vertical seismic component's influence. The results show that the influence of the vertical seismic component is considerable on the isolation layer especially under near-fault ground motions, so it should not be overlooked during the structural design; The change of isolation forms will greatly affect the influence of the vertical seismic component especially in the isolation layer and isolation systems with isolation devices set on higher stories or with less isolation layers will have less vertical seismic effect on story acceleration; The increase of the isolation period will globally result in the decrease of the influence of vertical seismic components, though in some cases it shows some sort of fluctuation before the final decrease; The increase of the friction coefficient will lead to the global decrease in the influence of the vertical seismic component in single-layer isolation structures, while it does not obviously affect those in the multi-layer isolation systems.