Parameter Optimization of a Vertical Spring‐Viscous Damper‐Coulomb Friction System

Abstract

A vertical spring-viscous damper-concave Coulomb friction isolation system was firstly proposed, and their parameters were firstly optimized to achieve the best performance under earthquakes. An incremental dynamic analysis method (IDA) and a performance-based assessment framework were used to calculate the system and assess its seismic vulnerability, respectively. Results show that both the friction force and the horizontal component of spring force gradually increase when an earthquake enforce the isolator to slide from its central location. Although other papers propose that an increase of spring force and a decrease of friction force can reduce the structural residual displacement, this paper can minimize the residual displacement value to be 0 by using a super lubrication in the middle of contact surface and a variable increment ratio of concave friction distribution. The reason is that the horizontal component of spring force is always greater than the friction force within any relative displacement between the structure and the ground in this paper. As for the peak relative displacement and peak acceleration of structure, one is reduced while the other is increased when selecting the optimal isolation parameters. If the structure is very sensitive to the acceleration response, a low friction parameter, a small spring constant, and a small and even zero damping constant could be adopted to yield a small peak acceleration of system. The tightness of vertical spring can be adjusted to be appropriately loose to continuously reduce the structural acceleration response.

Performance-based seismic isolation design using the theory of spatially concave friction distribution

“…However, the energy dissipation efficiency of frictional action is less than that of viscous damper [16]. Therefore, the viscous damper is still needed to reduce the structural relative displacement response, although the spatially concave friction distribution is used [17]. If the requirement of structural relative displacement is very loose during earthquakes, the expensive viscous damper is not needed and the seismic isolation system becomes a spring-friction system.…”

A Numerical Investigation on Scaling Rolling Friction Effects in Shaking Table Model Tests

“…e distribution range of these ratios RR becomes wider with an increase of the friction variation coefficient; however, it becomes less with an increase of the damping constant C. e latter rule is more obvious for case 3, with a more considerable friction variation in space. e reason is that the friction and the viscous damping have the same function of energy dissipation [33], and the increase in the damping constant reduces the influence of friction variation on the energy dissipation and seismic responses.…”

“…As the friction coefficient is a dimensionless quantity, it does not need to be scaled in theory. However, different friction coefficients are always distributed along the length of contact surface, which are described as the Coulomb friction changing in space in the second question [33]. ere is a new question: should the positions of specific friction coefficients move with the scaled length of contact surface?…”

Analysis of an Isolation System with Vertical Spring-viscous Dampers in Horizontal and Vertical Ground Motion

“…Therefore, it is necessary to study isolators that can simultaneously insulate horizontal and vertical vibration for earthquakes and excitations. Wei et al [36][37][38] published a related study on a vertical spring-viscous damper-concave Coulomb friction isolation system. However, this method was structurally simplified and optimized by the relation of force for the one-degree-of-freedom motion of the superstructure.…”