Performance assessment of the KDamper as a seismic Absorption Base

Abstract

Summary The KDamper is a novel passive vibration absorption concept based essentially on the optimal combination of appropriate stiffness elements, one of which has a negative value. In this paper, the implementation of the KDamper as a seismic Absorption Base (KDAB) is considered. The performance of the KDAB is assessed in three characteristic test cases, namely, a rigid body and two flexible buildings with fundamental periods of 0.5 and 1.0 s, respectively. In all three cases, the structures are excited by real and artificial accelerograms. The performance of the KDAB is compared not only with the original structure but also with the cases of conventional and highly damped base isolation systems, as well as with the case of a tuned mass damper inerter. Alternative options for the selection of the KDamper nominal frequency are considered, leading to two cases. In the first one, the nominal KDamper frequency is selected equal to the low frequency of a conventional base isolation system, resulting in a drastic improvement of the overall structural performance (i.e., superstructure accelerations and base drifts). In the second one, the KDAB is implemented with a much higher nominal frequency, leading to a drastic reduction of the relative base displacement, in the order of few centimeters, combined with acceptable structural performance. As a consequence, the KDamper can be implemented as a supplement of a conventional base isolation system or, alternatively, as a “stiff absorption base,” overcoming the disadvantages of seismic isolation approaches, leading towards new seismic protection technologies.

Feasibility Assessment of Stiff Seismic Base Absorbers

“…In the second and third cases, the SBA's maximum inerter coefficient is bmax=1 (100%) and 2 (200%) respectively. The performance of the SBA-AF is compared with the previous optimal design of KDamper, as presented in [37]. For this reason, two sets of parameters of each concept, that present similar results, in terms of the structure's dynamic responses, are selected and compared in Table 1.…”

Feasibility Assessment of Stiff Seismic Base Absorbers

“…The design of KDamper follows the procedure described in Kapasakalis et al [37], for optimal acceleration response, and is implemented as a stiff vibration absorber with a nominal frequency of 1 Hz. The Transfer Functions It is observed that the inerter manages to reduce the natural frequency f0, as in the case of the QZS oscillator, without having to reduce the stiffness of the system (Figure 2.B) or increase the seismic load ( Figure 2.A).…”

“…According to previous work of KDamper [32][33][34][35][36][37], an additional mass of 5% is efficient. In an effort to make the device more realistic and easier to implement, mD is selected as 0.1% of the structure mass.…”

“…The KDamper has been examined for the protection of bridge structures [23][24][25][26][27], Wind Turbines [28,29] and structural systems [30,31]. In addition, the KDamper is effectively implemented as an Absorption Base (KDAB) in the bases of structures [32][33][34][35][36][37].…”

Vibration Control of Offshore Wind Turbine Towers

“…The KDamper is essentially an extension of the traditional TMD, by introducing an appropriate negative stiffness (NS) element to the the oscillating mass of the TMD. The amplitude of the inertia force of the additional mass and the amplitude of the NS force are exactly in phase, due to the negative value of the implemented stiffness element [26,27]. Although the KDamper oscillator incorporates a NS element, it is designed to be statically and dynamically stable.…”