Effectiveness of resettable energy dissipating devices in seismic response modification of elastic SDoF systems

Abstract

Summary Semi‐active variable stiffness resettable devices can reduce seismic demands and damages in structures. Despite their advantages, variable stiffness resettable devices are under‐utilized mainly because of the shortage of fundamental research in quantifying the sensitivity of key seismic response parameters, and losses, in structures that use such systems for seismic hazard mitigation. Within this setting, the research summarized herein measures the effectiveness of semi‐active resettable energy dissipating devices in the Single‐Degree‐of‐Freedom domain aiming at quantifying the sensitivity of their seismic response to variation in control parameters and generating the required knowledge to utilize such semi‐active devices in the Multi‐Degree‐of‐Freedom domain. The performance (i.e. maximum relative displacement and peak absolute acceleration demands) of Single‐Degree‐of‐Freedom systems with an array of semi‐active control logics under various dynamic excitation regimes is studied. Two sets of 40 ground motions representing various seismic loading conditions (i.e. pulse‐like and rock‐site ground motions) are used, and an efficient control logic for mitigating these seismic demands is proposed. Numerical results show that proposed control logic enables a decrease of 40–60% for both maximum relative displacement and seismic base shear and 15–25% decrease for peak absolute acceleration. Copyright © 2016 John Wiley & Sons, Ltd.

Effects and distribution of semi‐active resettable springs on the seismic response of asymmetric structures

“…The device is used to vary or increase the stiffness of the system in real‐time. Fardadi et al 20 . investigated the seismic response of a SDOF system using a SRS whereby the stiffness is added through a bracing system, shown in Figure 1.…”

“…Three control laws were implemented in prior work, 20 denoted as 1‐4, 1&3, and 2&4, referring to the active quadrant of the figure representing the bracing system's load‐displacement curve. From the three control laws, it was found that control law 1‐4 was most effective in reducing the displacement of the frame.…”

“…The device is used to vary or increase the stiffness of the system in real-time. Fardadi et al 20 investigated the seismic response of a SDOF system using a SRS whereby the stiffness is added through a bracing system, shown in Figure 1. To quantify the amount of stiffness provided by the SRS, the brace-to-frame (BFS) factor is introduced, denoted by BFS, and defined as BFS = stiffness of the brace stiffness of the frame…”

“…SRSs provide energy dissipation while providing additional stiffness rather than damping control in MR dampers. Control algorithms for the utilization SRSs for seismic response reduction of symmetric structures were studied by several research groups on single-degree-of-freedom (SDOF) 20,21 and multi-degree-of-freedom (MDOF) [22][23][24][25] systems as well as experimental results. [26][27][28] A control algorithm for utilizing SRSs towards seismic response mitigation of asymmetric structures is presented herein.…”