•The negative stiffness inertial amplifier tuned mass dampers is introduced.•The new closed-form expressions for optimal design parameters of NSIA-TMDs.•The H2 and H∞ optimization based closed-form ...expressions for optimal design parameters.•NSIA-TMDs shows 50% better vibration reduction capacity than conventional TMD.
The negative stiffness inertial amplifier tuned mass dampers (NSIA-TMD) are introduced in this paper. Another two novel tuned mass dampers such as negative stiffness tuned mass damper (NS-TMD) and inertial amplifier tuned mass damper (IA-TMD) are mathematically developed from the negative stiffness inertial amplifier tuned mass dampers (NSIA-TMD) and the static masses of these three novel dampers are retained constant. The exact closed-form expressions for optimized system parameters for these novel dampers are obtained using H2 and H∞ optimization techniques. The dynamic responses of the SDOF systems controlled by H2 and H∞ optimized novel tuned mass dampers subjected to base excitations are obtained analytically. The dynamic response reduction capacities of the novel tuned mass dampers are compared with the dynamic response reduction capacities of traditional tuned mass dampers (TMD). Therefore, the dynamic response reduction capacities of H2 optimized NS-TMD, NSIA-TMD, and IA-TMD are significantly 45.51%, 43.47%, 41.08% superior to the H2 optimized traditional tuned mass dampers. Furthermore, the dynamic response reduction capacities of H∞ optimized NS-TMD, NSIA-TMD, and IA-TMD are significantly 3.31%, 8.98%, 13.79% superior to the H∞ optimized traditional tuned mass dampers. The nonlinear negative stiffness inertial amplifier tuned mass dampers (NNSIA-TMD) are also introduced in this paper. As a result, the dynamic response reduction capacities of H2 optimized nonlinear negative stiffness tuned mass damper (NNS-TMD), NNSIA-TMD, and nonlinear inertial amplifier tuned mass damper (NIA-TMD) are significantly 24.54%, 21.92%, 19.12% superior to the H2 optimized traditional tuned mass dampers. Furthermore, the dynamic response reduction capacities of H∞ optimized NNS-TMD, NNSIA-TMD, and NIA-TMD are significantly 3.01%, 9.04%, 15.08% superior to the H∞ optimized traditional tuned mass dampers. The outcomes of this research are mathematically accurate and relevant to practical design applications.
Summary
Tuned mass dampers (TMDs) represent a quite mature technology for controlling human‐induced vibrations of footbridges, when they are tuned to the primary structure's fundamental frequency. ...However, the TMD is very sensitive to even a small change in the tuning ratio. This paper proposes a novel TMD named self‐adjustable variable mass TMD (SAVM‐TMD), which is capable of varying its mass and retuning its frequency on the basis of the acceleration ratio between the primary system and the TMD. The accelerations are obtained from two acceleration sensors, and the frequency adjustment is achieved by using a microcontroller and actuating devices. The acceleration ratio limit value should be set in the microcontroller firstly, and when the adjustment begins, the microcontroller will retune the TMD to a reasonable frequency region, under a specific harmonic excitation. The SAVM‐TMD can be regarded as a passive control device capable of adjusting its frequency. The performance of SAVM‐TMD is studied via both experimental studies and numerical simulations under different pedestrian excitations. It is found that the SAVM‐TMD is effective in reducing the response and improving the equivalent damping ratio of the primary system when the structural frequency changes, with little power consumption. The results obtained from the experimental studies and the numerical simulations agree with each other very well. More pedestrian vibration situations are studied in the numerical simulations, and the results also show that the SAVM‐TMD has excellent performance in controlling human‐induced vibrations.
A state-of-the-art review on the response control of structures mainly using the passive tuned mass damper(s) (TMD/s) is presented. The review essentially focuses on the response control of wind- and ...earthquake-excited structures and covers theoretical backgrounds of the TMD and research developments therein. To put the TMD within a proper frame of reference, the study begins with a qualitative description and comparison of passive control systems for protecting structures subjected to wind-imparted forces and forces induced due to earthquake ground motions. A detailed literature review of the TMD is then provided with reference to both, the theoretical and experimental researches. Specifically, the review focuses on descriptions of the dynamic behavior and distinguishing features of various systems, viz. single TMD (STMD), multiple tuned mass dampers (MTMDs), and spatially distributed MTMDs (d-MTMD) which have been theoretically developed and experimentally tested both at the component level and through small-scale structural models. The review clearly demonstrates that the TMDs have a potential for improving the wind and seismic behaviors of prototype civil structures. In addition, the review shows that the MTMDs and d-MTMDs are relatively more effective and robust, as reported. The paper shows the scope of future research in development of time and frequency domain analyses of structures installed with the d-MTMDs duly considering uncertainties in the structural parameters and forcing functions. In addition, the consideration of nonlinearity in structural material and geometry is recommended for assessment of the performance of the STMD, MTMDs, or d-MTMDs.
The combination of negative stiffness devices and inerters to traditional base isolators (TBI) and tuned mass dampers (TMD) does not exist in any state-of-the-art. Therefore, to pursue the research ...using the above-mentioned research scope, the negative stiffness inerter passive dampers such as negative stiffness inerter-based base isolators (NSIBI), negative stiffness base isolators (NSBI), negative stiffness inerter-based tuned mass dampers (NSITMD), and negative stiffness tuned mass dampers (NSTMD) are introduced in this paper. H2 and H∞ optimization methods are applied to derive the exact closed-form expressions for the optimal design parameters of these novel passive vibration dampers. Newton’s second law applies to derive the governing equations of motion of the controlled structures. The transfer function formation and Newmark-beta method are applied to determine the dynamic responses of the controlled structures analytically and numerically. Hence, H2 optimized NSIBI and NSBI have 45.98% and 46.71% more dynamic response reduction capacities than optimum TBI. In addition, H∞ optimized NSIBI and NSBI have 58.36% and 57.32% more dynamic response reduction capacities than optimum TBI. Furthermore, the optimum NSITMD and NSTMD have 0.42%, 10.84%, and 4.5%, 13.48% more dynamic response reduction capacities than traditional TMD. All the derivations are mathematically accurate.
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•Combination of NSD and inerters to TBI and TMD does not exist in state-of-the-art.•Negative stiffness inerter passive dampers are introduced.•H2 and H∞ optimized design parameters are introduced.•Vibration reduction capacities of NSIBI and NSBI are 45% more than TBI.•NSITMD and NSTMD have 10% more vibration reduction capacities than TMD.
Compared with fixed offshore wind turbines, the vibration problem of floating offshore wind turbines is particularly prominent, and further reduction of the vibration of floating offshore wind ...turbines has become an engineering challenge. In order to solve this problem, a novel vibration suppression device, inerter-based absorber (IBA) is introduced, and the vibration control of semi-submersible offshore wind turbines is studied. A comprehensive optimization method, namely the structure-immittance approach, is utilized to design the IBA in a systematic way. In order to search for the optimum vibration suppression performance, a simplified dynamic model of the semi-submersible offshore wind turbine, and the IBA dynamic equations are established using D’Alembert’s principle. Simultaneous suppression of the vibration response of the floating platform and tower of a semi-submersible offshore wind turbine is realized using the dual IBA control strategy. Furthermore, by implementing the optimum IBA in the OpenFAST
Tall chimneys have become necessary due to growing industries and changing environmental norms. Chimneys are tall and slender structures and thus they are sensitive towards wind loads. Thus, it ...becomes necessary to analyze their performance along both the direction i.e. along the wind and across the wind accurately, and to improve their performance by providing suitable measures. Now a days, Tuned Mass Dampers (TMDs) are provided to improve the performance of structures against dynamic loadings However, there are very few reported studies on the effect of TMDs on wind response control of tall chimneys. Hence, it is important to paper the use of different TMD systems and their performance in chimneys. Two RC chimneys of height of 200 m and 220 m of varying thickness are considered for dynamic wind paper using CFD in ANSYS. Modal response of chimney without and with TMD are also studied. The spring mass analogy is used for the connection of chimney and Tuned Mass Dampers. Gust Factor Method as per IS 875 (III) 2015 and IS 4992-1992, for along and across wind load calculation has been studied. Excel Programme file also prepared for the analysis of wind loads using IS codes. Three TMD systems are considered viz. Single Tuned Mass Damper system (s-TMD) and Multiple Tuned Mass Damper system (m-TMD-1 and m-TMD-2).The analysis results of TMD system are compared with the results of without TMD system. The results are compared on the basis of peak displacements of chimney. It has been found that Multiple TMD systems are more effective than Single TMD system. The reduction in deflection of about 25–30% is observed for m-TMD systems.
