Vertical seismic isolated rocking-core system

Abstract

Mass isolation of structures is an efficient vibration-control technique for reducing earthquake effects on buildings. This paper introduces a vertical seismic isolated rocking-core system (VSI-RCS) in which a controlled rocking-core is separated from the frame by viscous fuses. The controlled rocking-core provides the self-centring capability while the viscous dampers limit the lateral displacement and dissipate the majority of the seismic energy. An analytical solution is proposed for estimation of the optimal damping constant of the dampers along with the corresponding fundamental frequencies and damping ratio of the VSI-RCS. A parametric study was carried out to quantify non-classical dynamic characteristics and spectral analysis was performed to examine the seismic performance of the VSI-RCS compared with rocking-core systems. The proposed formulas were found to be applicable for rapid eigen-analysis and, compared with non-isolated rocking-core systems, proper seismic efficiency of the VSI-RCS was observed.

Structural optimization of vertical isolated rocking core-moment frames

“…As can be seen, the considered variables for optimization analysis have considerable effects on responses. For further details on the non-classical solution of VI-RCMFs, refer to Nekooei et al (2020)…”

“…The considered search spaces for variables of X k are 0.1≤ α m ≤1, 0.1≤ α k ≤10, 0≤ ξ d ≤0.125. The upper bound of 0.125 is equal to 50% of the maximum damping ratio of the damper, ξdmax (Nekooei et al, 2020). As shown in Figure 4, the ξdmax can be 0–25% for different ranges of mass and stiffness ratios.…”

“…Several techniques are developed to minimize this drawback using either special detailing for MFs (Huang et al, 2020; Grigorian, 2021) or isolating RCs and MFs. Accordingly, a novel seismic vertical isolated RCMF (VI-RCMF) (Nekooei et al, 2020) has been recently introduced to mitigate the vulnerability of the MF sub-system. The VI-RCMFs is a unique passive control system equipped with viscous energy dissipation devices, as shown in Figure 1.…”

“…Moreover, the seismic acceleration and velocity of VI-RCMFs as well as the RC displacement are lower than RCMFs. Although the displacements of long-period isolated archetypes are lower than non-isolated counterparts, the deformations of MF subassemblies are higher for low-and mid-rise archetypes (Nekooei et al, 2020). Accordingly, the proper design parameters need to be adjusted for minimizing the MF displacement.…”

Functional recovery evaluation of hybrid self‐centering piston‐based braced frames

“…Examples of such systems encompass self-centering braced frames, [26][27][28][29] controlled rocking-core systems, [30][31][32][33][34] multiple rocking joints, 35,36 and isolated rocking cores. 37,38 While these innovative structural systems are designed to withstand seismic forces with minimal damage, they encounter challenges related to functional recovery. One significant challenge is the potential damage to non-seismic frames caused by the substantial displacements of self-centering cores, impacting structural connections and stairs, and hindering post-earthquake functionality and recovery efforts.…”