No abstract

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%.

In this paper, attempts are made to investigate the responses of torsionally coupling base-isolated structure supported on Triple Concave Friction pendulum bearing (TFP) subjected to near field ground motions. Nonlinear dynamic analyses are conducted to study the effects of essential parameters such as superstructure and isolation system eccentricity, and the uncoupled torsional to lateral frequency ratio of superstructure on seismic responses of TFP isolated structures. Further, the responses of base-isolated structure using TFP are compared with the same base-isolated structure using friction pendulum system (FPS) as well as double concave friction pendulum (DCFP). Results indicate that TFP isolated structure significantly outperforms other types of friction bearings. Moreover, increasing effective period causes TFP isolated structures to behave better than the others in reducing torsional responses of structure. It is concluded that effectiveness of TFP isolators in respect to others bearings is negligible on seismic responses of structures through increasing effective damping.

No abstract

In this research, the effects of rotational components of earthquakes on seismic responses of Triple Concave Friction Pendulum (TCFP) base-isolated structures are investigated elaborately. Although it is common to ignore the influence of rotational components of earthquakes on structural analysis, this investigation demonstrates the significant effects of these components on seismic responses of isolated structures mounted on TCFP bearings. Extensive base-isolated structures models with different superstructure specifications such as slenderness and aspect ratios as well as isolation properties such as effective period and damping are investigated. Essential seismic responses such as base shear, roof acceleration, isolator displacement and base slab rotation are studied while isolated structures subjected to the translational components of earthquakes as well as the rotational and translational components of earthquakes simultaneously. The results demonstrate the sensitivity of seismic responses to the superstructure properties such as the slenderness ratio and plan aspect ratio in presence of rotational components; whereas it does not show such sensitivity to isolation properties. Generally, the roof acceleration and the base shear can be affected by the rotational components, tremendously. For instance the roof acceleration can be raised 220% in a structure when its plan length is three times more than its plan width and the base shear can be increased 33% for a 9-story building in presence of rotational components.