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The effectiveness of the tuned mass damper inerter (TMDI) in reducing the vibration of building structures under site-specific earthquake excitation is investigated. The site is Guwahati, Assam, which lies in the most severe seismic intensity zone in India. In this paper, the optimization of the TMDI design parameters is carried out for the site-specific input derived for the building site by a modulated Clough-Penzien (C-P) spectrum fitted to the power spectral density function obtained from a strong motion model of the site. All possible topologies of the TMDI, with one terminal of the inerter being connected to the damper mass attached to the top storey of the example buildings, and the other terminal being connected to any other floor, are investigated. The structure-TMDI system is analyzed both in the frequency-domain and in the time-domain. A numerical study is conducted with two example building structures. Optimization of design parameters of the TMDI is carried out using the technique of simulated annealing in the frequency-domain using the site-specific modulated Clough-Penzien spectrum as input. The performance of the optimal TMDI cases is evaluated by subjecting the example structures to 10 site-specific synthetically generated accelerograms. Results indicate that the TMDI is superior to the TMD for all topologies of the TMDI in case of the 3-storieed structure; and for topologies of the TMDI in which the inerter spans more than 4 floors for the 8-storied structure, with improved reductions in top-floor displacement, acceleration, and stroke length. [ABSTRACT FROM AUTHOR]

Sloshing water in the overhead water tank of a multi-storeyed building may be utilized to act as a tuned liquid damper for vibration control under wind and earthquake excitation. In conventional rectangular or circular water tanks, tuning presents difficulties as the sloshing frequency varies significantly with change in the depth of water in the tank. To address this issue, in this paper, we find shapes of tanks wherein the sloshing frequency is essentially independent of water depth over a large and useful range of water levels. Both two-dimensional as well as axisymmetric (three-dimensional) tank shapes are found. We use a direct boundary element method to find the sloshing frequencies in each case. In each case, a tentative simple analytical form for the tank shape is chosen with three free parameters, and these parameters are adjusted to obtain shapes where the first lateral sloshing frequency has negligible variation with water depth. For axisymmetric tanks, the circumferential (azimuthal) variation in field variables is restricted to the first harmonic, in the interest of lower computational effort. For both planar and axisymmetric cases, the working range of water depths is taken to be from 0.2 to 2 times the tank width. In both cases, the variation in first lateral sloshing mode frequency is found to be under 0.2% over the working range. In comparison, for constant width tanks such as the rectangular or circular ones, over the same range of water depths, the corresponding variation is more than 60 times greater. [ABSTRACT FROM AUTHOR]

The Ccmpliant Liquid Column Damper (CLCD) is a variation of the conventional Liquid Column Damper (LCD) that is applicable for the vibration control of relatively short period structures. Along with the long period structures short period structures are also highly vulnerable to the seismic excitation, as the frequency content of earthquake excitation is generally more broad-banded and richer in high frequency as compared to that of wind excitation. In the present study the equations of motion of the SDOF structural system with attached CLCD are formulated and a time domain parametric study with real earthquake input data is carried out. For a short period model structure the sensitivity of the design damper parameters are investigated and optimum values of the same are identified. Further, an experimental study on a base-excited stiff scaled structural model with CLCD is carried out for white noise and random loading. Identification of designed structural model followed by an experimental sensitivity study of the CLCD design parameters are presented. The optimal values of design parameters are identified and the performance of the optimally designed CLCD is examined for random base excitation. The efficacy of the CLCD for vibration mitigation of short period structures is thereby validated. [ABSTRACT FROM AUTHOR]

This paper focuses on the seismic vibration control of elevated water tanks (EWTs) by the passive tuned liquid damper (TLD). Because of the fluctuating water content, the EWT is a variable-mass system resulting in a continual modification of its natural frequencies. The problem of identifying the optimal tuning of the damper for robust performance over the range of fill depths of interest in the EWT is addressed here. The nonlinear model based on shallow water wave theory simulating sloshing motion of the liquid (here water) in the TLD is utilized. The sloshing of water in the EWT itself is considered by modeling the EWT as a two-degree-of-freedom system, one representing the lateral vibrational mode of the supporting tank structure, tank container and impulsive mass of the water and the other denoting the fundamental sloshing mode of the water. A time domain study on a realistic reinforced concrete shaft supported EWT with TLD subjected to harmonic and recorded accelerogram input indicates that the TLD achieves significant response reduction and that it should be tuned to the structural frequency corresponding to the half-full to three-fourth full tank condition for robust performance. [ABSTRACT FROM AUTHOR]