A constant friction coefficient model for concave friction bearings

This paper develops a constant friction coefficient model that best represents a velocity-dependent friction model for predicting structural response of buildings isolated with concave friction bearings. To achieve this goal, the effect of friction model on structural response of three hypothetical isolated buildings with different number of stories subjected to different earthquake scenarios was numerically investigated. The structural numerical models of the isolated buildings were developed in OpenSees with superstructure is represented by a shear frame model and isolation system using single friction pendulum bearings is modeled by a 3-D friction pendulum bearing element which accepts different friction models. The numerical models were subjected to 30 pairs of ground motions, representing service earthquake level, design basic earthquake level and maximum considered earthquake level at a strong seismic activity area in the world. The investigation reveals that friction coefficient models significantly affect the structural response and there is no constant friction coefficient model that simultaneously best predicts isolation system response and superstructure response. The constant friction coefficient that best predicts isolation system response produces a large error on prediction of superstructure response and vice versa. Based on the numerical results, a constant friction coefficient model for different criteria was developed. Keywords: friction coefficient model; friction bearing; isolation system; earthquake response; time-history analysis.

INFLUENCE OF MACRO AND MICRO DEFLECTIONS ON LOADING CAPACITY, FLOW RATE AND ENERGY CHARACTERISTICS OF FLUID FRICTION BEARINGS

The influence of technological deviations on the performance of fluid friction bearings is considered. A mathematical model of a hydrodynamic sliding bearing is presented, based on a joint numerical solution of the Reynolds equation and additional relations to take into account the microroughness of the bearing surfaces. Analysis of the numerical results made it possible to assess the effect of roughness on the bearing capacity, consumption and energy characteristics of fluid friction bearings.

CONTROLLABLE TEMPERATURE AND VISCOSITY WEDGE EFFECT IN FLUID FRICTION BEARINGS: RESULTS OF PHYSICAL EXPERIMENTS AND DESIGN OF A DIGITAL TWIN

The paper considers the use of lubricants with different temperatures and multi-zone supply of liquid for lubrication. The best lubrication combinations were identified, and graphical images of sensors were presented for better analysis. A simulation model of the rotary support system is designed, which also includes models of motion sensors and converters.

THE ANALYSIS OF THE TRAJECTORIES OF MOTION RIGID ROTOR IN THE CONICAL LIQUID FRICTION BEARINGS

The calculation procedure of the trajectories of motion of the rigid rotor in the conical liquid friction bearings is offered. The equations set of motion is written for two-bearing rotor in the conical liquid friction bearings.The results are illustrated by the plots of trajectories for the conical bearings with oil lubricant.

Numerical Simulation of Frictional Heating Effects of Sliding Friction Bearings for Isolated Bridges

Sliding friction bearings are effective passive devices to mitigate the seismic responses of structures. Extensive researches have been conducted on sliding bearings. However, most previous studies were based on the assumption that the effects of frictional heating are negligible. A three-dimensional thermal-mechanical-coupled finite element (FE) model of the friction pendulum system (FPS) was developed in this study. Good agreements between the numerical results and the data measured in the previous tests, in terms of the force–displacement curves and temperature time-histories, indicate that the proposed FE model can predict the response of the FPS. Based on the developed FE model, the surface temperature distribution, the effective stiffness and the energy dissipation of the double concave friction pendulum and multiple friction pendulum bearings were investigated and compared. In addition, the thermal states of the sliding bearings in the bridge during earthquake were evaluated. The numerical results indicate that the temperature rise in the sliding bearings leads to the degradation of the effective stiffness and less energy dissipation. The relative displacements of the bearings increase considering the frictional heating effects in the bearings. If the frictional heating of the bearings is ignored, the peak bearing displacements will be underestimated.