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Difficulty in maintaining tuning due to water depth fluctuation makes overhead water tanks (OWTs) ineffective as tuned liquid or mass dampers. Recently, a semi-active damper involving OWT, that varies the stiffness of the tank-supporting columns with liquid depth variation to maintain the impulsive frequency of the tank constant at a value required for tuning, has been proposed. In this paper, the concept is extended to develop a passive tuned damper involving the OWT (PTD-OWT), which is more reliable, cost-effective, and has a simpler configuration than its semi-active counterpart but achieves the same objective as the latter. For the PTD-OWT, a novel mechanism involving a spring-supported platform, a rigid frame, and tank-supporting columns is developed. The working principle and mathematical model of the PTD-OWT are presented followed by an illustrative design example considering the host building undergoing base excitation. The results revealed that the PTD-OWT remains tuned and thereby performs consistently despite wide variations in water depth in the tank. Significant reductions have been achieved by the PTD-OWT in peak and root-mean-square displacement and acceleration responses of the structure for a variation in liquid depth between 100% full tank to empty tank condition, with the maximum fall in control achieved as only 6.8%. A comparison of PTD-OWT is made with the case when the tank is designed as a conventional passive tuned mass damper (TMD) without the provision for maintaining tuning. The conventional mass damper suffers significant performance degradation as liquid depth fluctuates in the tank. [ABSTRACT FROM AUTHOR]

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]

This paper focuses on the dynamics of a submerged compound pendulum (SCP). The considered pendulum consists of a horizontal cylindrical element at its lowermost portion and a plate between the cylindrical element and the pivot. An approximate analytical expression for the natural frequency of the submerged compound pendulum is proposed. Further, a two-dimensional (2D) numerical model of the pendulum is developed using ANSYS (FLUENT). The natural periods of the SCP are determined for different geometric configurations. The analytically estimated natural periods of the pendulum match well with those obtained from numerical simulation. [ABSTRACT FROM AUTHOR]

In a laterally excited, partially liquid-filled U-shaped container, oscillation is the predominant motion of the liquid. However, there would be some sloshing in the liquid free surface at the vertical limbs of the container. Due to the presence of high-energy velocity pulses, near-fault ground motions can cause significant sloshing in the vertical limbs of the container. Thus, it is necessary to examine the effect of near-fault earthquake excitations on the sloshing liquid height, sloshing-induced hydrodynamic pressure, and shear stress at the walls of the U-shaped containers. The same is attempted in this paper. The standard "k-epsilon" turbulence model with enhanced wall function is considered in this study. The outcome of this study reveals that the time-wise frequency variation of the near-fault ground motions significantly affects the sloshing response of the liquid stored in the U-shaped containers. It is observed that the sloshing-induced hydrodynamic pressure is severely influenced by the frequency content of the ground motion records rather than their peak ground acceleration. [ABSTRACT FROM AUTHOR]

Passive tuned liquid dampers, being cost-effective, easy to implement, and reliable structural vibration control devices, have received significant attention from designers and researchers. Considerable works devoted to the extraction of higher damping, increase in volumetric efficiency, improvement in architectural adaptability, and use in a large spectrum of structures have led to the development of a variety of configurations of passive tuned liquid dampers. Rigorous research efforts are being devoted to the utilization of different forms of tuned liquid dampers for the vibration control of buildings, bridges, chimneys, wind turbines, etc. However, till now, only a few varieties of tuned liquid dampers have been implemented in real-life structures, while the others require further refinement. This necessitates the present work, through which a systematic review on tuned liquid dampers of various configurations for structural response reduction is presented, with a focus on the design of the dampers. To organize the review in a structured manner, the large family of tuned liquid dampers is categorized into five groups based on their energy dissipation mechanism, namely the tuned sloshing damper, tuned liquid column damper, combined tuned sloshing damper-tuned liquid column damper system, compliant liquid damper, and liquid damper with submerged tuned oscillator. The modeling, analysis, design, and performance-related aspects of the different varieties of tuned liquid dampers are covered. The advantages and applicability of the different types of tuned liquid dampers are highlighted along with their real-life installations. The current gaps in the development of the various tuned liquid damper configurations and scope of future developments are also identified. [ABSTRACT FROM AUTHOR]

An appendage, in the form of a submerged suspended plate (SSP) in a liquid-containing deep tank, is proposed for converting functional liquid storage tanks into passive tank dampers for structural vibration mitigation. The oscillating frequency of the SSP is designed to be tuned to the structural frequency so that the tank damper is independent of detuning effects that could be caused by liquid level fluctuations. Further, the impulsive, rather than the sloshing, liquid mass is utilized here. This alleviates the disadvantage of low energy dissipation associated with the relatively smaller proportion of sloshing liquid mass of a deep tank. The theoretical model and working mechanism of the deep tank damper with submerged suspended plate (DTD-SSP) are developed and the expression for the tuning frequency derived. A time-domain formulation for the structure-DTD-SSP system is presented and the design and effectiveness of the DTD-SSP for an example structure under base excitation examined. Further, the performance sensitivity to tuning ratio and comparison with the traditional tuned mass damper (TMD) are presented. Results indicate that with the proposed design, liquid storage tanks installed for other functional requirements can be converted into DTD-SSPs that can achieve significant response reductions comparable with that of TMDs. [ABSTRACT FROM AUTHOR]

Despite the proven effectiveness of tuned liquid dampers (TLDs), readily available liquid storage tanks are rarely utilized for vibration control of laterally-excited structures, as these are deep tanks with low inherent damping. Further, the fluctuation in liquid level in these tanks also causes variation in the fundamental sloshing frequency, leading to detuning. To overcome these problems, a novel TLD with floating base (TLD-FB) is proposed, in which a constant and shallow liquid level is maintained between the free liquid surface and the floating base. The liquid above the floating base acts as a conventional shallow TLD that always remains tuned to the structural frequency. The paper demonstrates how the TLD-FB can be incorporated into a water storage tank system on an example building without disturbing its functionality and achieves structural response reduction, despite water level fluctuations in the tanks. [ABSTRACT FROM AUTHOR]

The possibility of controlling two modes of structural vibration due to earthquake excitation by considering the sloshing action in the vertical limbs of the liquid column vibration absorber (LCVA) has been explored in this paper. The structure has been modeled as a linear, viscously damped multi-degree-of-freedom (m.d.f.) system. The governing differential equations of motion for the damper liquid and for the coupled structure-LCVA system have been derived from dynamic equilibrium. The nonlinear orifice damping in the LCVA has been linearized by a stochastic equivalent linearization technique. A displacement transfer function formulation for the structure-LCVA system has been presented. The study has been carried out on a 2-d.f. example structure for which both the modes have significant contribution to the total response. The performance of the LCVA has been evaluated in the frequency domain with the base input characterized by a white noise power spectral density function and through a simulation study by subjecting the example structure-LCVA system to a recorded accelerogram. The results are compared with that of the liquid column damper and indicate superior performance of the LCVA. Furthermore, an LCVA has been designed for the example structure. [ABSTRACT FROM PUBLISHER]

The potential of the liquid column vibration absorber (LCVA) as a seismic vibration control device for structures has been explored in this paper. In this work, the structure has been modeled as a linear, viscously damped single-degree-of-freedom (SDOF) system. The governing differential equations of motion for the damper liquid and for the coupled structure-LCVA system have been derived from dynamic equilibrium. The nonlinear orifice damping in the LCVA has been linearized by a stochastic equivalent linearization technique. A transfer function formulation for the structure-LCVA system has been presented. The design parameters of the LCVA have been identified and by applying the transfer function formulation the optimum combination of these parameters has been determined to obtain the most efficient control performance of the LCVA in terms of the reduction in the root-mean-square (r.m.s.) displacement response of the structure. The study has been carried out for an example structure subjected to base input characterized by a white noise power spectral density function (PSDF). The sensitivity of the performance of the LCVA to the coefficient of head loss and to the tuning ratio have also been examined and compared with that of the liquid column damper (LCD). Finally, a simulation study has been carried out with a recorded accelerogram, to demonstrate the effectiveness of the LCVA. [ABSTRACT FROM AUTHOR]