Effect of vertical component of earthquake on seismic responses of triple concave friction pendulum base-isolated structures

The current investigation has been conducted to examine the effect of the vertical component of earthquake on the responses of base-isolated structures mounted on a triple concave friction pendulum (TCFP) bearing. The varying inherent stiffness and damping of this new generation of friction isolators make smart behavior to mitigate damages during different earthquake hazard levels. To investigate, the structure was idealized as a two-dimensional single story (single degree of freedom) resting on a TCFP isolator and the coupled differential equations of motion were derived and solved using state-space formulation. Based on these equations, a computer program was developed to study the influence of the vertical component of earthquake on the seismic responses of a TCFP isolated structure such as bearing displacement and base shear of the isolated structure. The variation of essential parameters such as superstructure period, isolation period and friction coefficient of sliding bearing surfaces was studied when the TCFP isolated structure was subjected to seven near field earthquake motions. This study demonstrates the significant effects of the vertical component of earthquakes on seismic responses of base-isolated structure mounted on TCFP bearings, which is why the maximum error caused by neglecting the vertical component of earthquake in calculating the base shear of the structure is 29.5%.