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In contrast with the odd number based multiple tuned mass dampers (ON-MTMD) used conventionally, which is targeted at the central natural frequency, the arbitrary integer based multiple tuned mass dampers (AI-MTMD) is proposed for the convenient applications of MTMD by giving up the central natural frequency hypothesis. The total number of the TMD units constituting the AI-MTMD may be selected as an arbitrary integer according to the practical requirements. In terms of the dynamic magnification factors (DMF) of the AI-MTMD structure system, the criterion for evaluating the optimum parameters and effectiveness of the AI-MTMD is selected as the minimization of the minimum values of the maximum DMF of the structure with the AI-MTMD. Employing the maximum DMF of every mass block in the AI-MTMD, the stroke of the AI-MTMD is simultaneously evaluated. The results indicate that both the AI-MTMD and the ON-MTMD can practically render the same performance, thus demonstrating that the former can be more convenient in mitigating structural oscillations with respect to the ON-MTMD stuck to the central natural frequency hypothesis.

Intelligent and adaptive control systems are naturally suitable to deal with dynamic uncertain systems with non-smooth nonlinearities; they constitute an important advantage over conventional control approaches. This control technology can be used to design powerful and robust controllers for complex vibration engineering problems such as vibration control of civil structures. Fuzzy logic based controllers are simple and robust systems that are rapidly becoming a viable alternative for classical controllers. Furthermore, new control devices such as magnetorheological (MR) dampers have been widely studied for structural control applications. In this paper, we design a semi-active fuzzy controller for MR dampers using an adaptive neuro-fuzzy inference system (ANFIS). The objective is to verify the effectiveness of a neuro-fuzzy controller in reducing the response of a building structure equipped with a MR damper operating in passive and semi-active control modes. The uncontrolled and controlled responses are compared to assess the performance of the fuzzy logic based controller.

In the paper, the dynamic control of structural vibrations in ancient constructions is considered. Since the constituent material of the structure exhibits poor tensile resistance, an effective performance of the algorithm requires the nonlinearity of the structure to be considered at the very first stage of the design of the control algorithm. Inclusion of the material nonlinearity of the structure into the design of the control mathematical rule presents a number of issues of high complexity either from the theoretical or computational aspects, which make the topic poorly treated in literature, in particular through full mathematical approaches. In the first part of this paper, one sets up a full model for analysis of the spatial masonry constructions with holonomic plasticity taken into account, and, in the second part, one formulates an algorithm aimed at mitigating the dynamic effects on the structure. The implementation of the control algorithm, the development of original calculus codes and the numerical investigations show the high potential of the proposed approach in significantly improving the performance of the structure.

This paper presents a sensitivity analysis on the performance of optimal proportional–integral–derivative (PID) controller for use in nonlinear smart base-isolated structures with uncertainties. A set of nine performance indices is defined to evaluate the performance of the controller in the presence of uncertainties in the superstructure, lead rubber bearing (LRB) seismic isolation system, and applied loads. The time delay effect on the stability and performance of the PID controller is also examined. The results show that the PID controller is robust against the uncertainties up to $\pm 15$% in the damping and stiffness coefficients of the superstructure, the yield force of the LRB and the artificial earthquake. In the case with $\pm 15$% of uncertainty, the input energy entering into the structure is increased with respect to the nominal model. However, the changes of the performance indices related to the damage energies are negligible. An uncertainty of $-$20% in the stiffness coefficient and stiffness ratio of the LRB gives an increase of 15% in the maximum and root mean square (RMS) of the structural responses. In the case with $-$20% of uncertainty, the damage and damping energies do not change in comparison with the case of the nominal model, but a significant decay in the performance index related to the input energy response is obtained in this case. Not all performance indices are sensitive to time delay. For large time delays, the performance index for the seismic input energy increases significantly, while the maximum damage and damping energies increase up to 5% and 10%, respectively.

A footbridge is a structure designed for pedestrians or animals to cross roads, water or railways, safely. Modern ones are designed as slender and light structures to be more aesthetic and economic, but may lack enough stiffness and damping that might produce excessive vibrations under service conditions, overpassing comfort limits for users and compromise structural integrity. This work presents the synthesis of a nonlinear optimal control strategy for reducing vibrations in footbridges by means of using magnetorheological dampers. The proposed optimal controller considers both, the footbridge linear dynamics and the damper nonlinear dynamics, as the complete system to be controlled. For analysis purposes, the continuous structure of a footbridge is conveniently idealized as an $N$-degrees-of-freedom discretized model, such that it can be handled as an $N$-order system. Parameters from an actual footbridge are used to propose a discretized model system of 11 translational degrees of freedom and to analyze the system response as a case study. The dynamical response involves displacement, velocity and acceleration for different number of pedestrians crossing in groups. The investigation rests on comparing the structural response over time for two different conditions: with no control device installed and with one magnetorheological damper installed at the span center. Results obtained with the use of the proposed optimal controller show to be an effective way of reducing the structural motion response.

This study aims for a probabilistic assessment of active seismic control of structures in the presence of uncertainties of the structural model and the stochastic model of the ground acceleration. First, sensitivity analyses based on the Borgonovo sensitivity index are conducted to measure the effect of uncertainty sources on the maximum and root mean square (RMS) of the main structural responses in different seismic hazard regions. Then, the reliability analyses are conducted using Monte Carlo simulation (MCS) and importance sampling (IS) methods to the estimation of failure probabilities and reliability indices of the structures in different seismic hazard regions, force capacity of actuators, and seismic performance levels. Numerical studies carried out on a 10-story structure show that the uncertainties in peak ground acceleration (PGA) and story stiffness have the most effects on the seismic responses of the structure. The effect of the considered uncertainties is negligible on the maximum demand control force. The results also show that equipping the structure with an active control system results in a significant reduction in the failure probabilities of the structure. The target reliability index for the uncontrolled structure in life safety seismic performance level may not be satisfied in high and very high seismic hazard regions, it can however be easily dealt with, using the proposed technique, in the corresponding controlled structures. By increasing the control force capacity, an increment is observed in the reliability index. A high and suitable reliability index is given for both controlled and uncontrolled in the collapse prevention seismic performance level.

The toroidal tuned liquid column damper (TTLCD) has been known so far only for its multidirectional vibration control capabilities. The details of its liquid motion characteristics and energy dissipation capacity have been missing. To cover this gap, in this paper, experimental studies are carried out by shaking table tests and an effective three-dimensional computational fluid dynamics model of the TTLCD is developed. All parametric effects and the characteristics of the liquid motion in the TTLCD are addressed. The findings of the paper now clearly reveal that the TTLCD encompasses both an oscillatory liquid deflection as the first mode and a sloshing motion as the second mode vibration response. Accordingly, the results prove that the TTLCD operates not only multidirectionally but also as a unique multimodal device, which unites the properties of tuned liquid dampers (TLDs)/tuned sloshing dampers (TSDs) with tuned liquid column dampers (TLCDs).

The paper presents a parametric optimization of Tuned Liquid Column Damper (TLCD) to control the structural vibration of 5MW NREL offshore wind turbine (OWT) subject to the wind and waves random forces. In this work, the fluid–structure interaction of monopile with seawater are modeled as an added mass and the soil-structure interaction of monopile foundation is considered through simplified model of discrete coupled springs model. Using a proprietary genetic algorithm, the TLCD on nacelle has its parameters optimized to reduce the standard deviation or roots mean square (RMS) dynamic response on tower top. The displacement results are compared to the ones obtained by exhaustive search methods via a response map. From the stochastic analysis of the structure response, the ideal tuning ratio and damping ratio are determined for the liquid column damper to present its highest efficiency, i.e. the lowest RMS displacement at the tower top. The damper parameters achieved by both optimization methods show a significant agreement between them. In addition, the use of the genetic algorithm, a parametric optimization of the TLCD installed in OWT is carried out considering the random excitation of the wind, wave, and rotor forces (Kaimal, JONSWAP, and rotational spectra, respectively). In possession of the TLCD optimal parameters determined by the parametric study, the mitigation of displacements at the standard wind turbine top is analyzed. The fore-aft vibration at tower top with a TLCD attached shows a significant reduction for actions dynamic components. Finally, TLDC optimal parameters have a direct relation with the considered force spectrum and the turbine transfer function, and both must be considered for the damper optimization process.

Structural controllability is the generalization of traditional controllability for dynamical systems. During the last decade, interesting biological discoveries have been inferred by applied structural controllability analysis to biological networks. However, false positive/negative information (i.e. nodes and edges) widely exists in biological networks that documented in public data sources, which can hinder accurate analysis of structural controllability.

In this study, we propose WDNfinder, a comprehensive analysis package that provides structural controllability with consideration of node connection strength in biological networks. When applied to the human cancer signaling network and p53-mediate DNA damage response network, WDNfinder shows high accuracy on essential nodes prediction in these networks. Compared to existing methods, WDNfinder can significantly narrow down the set of minimum driver node set (MDS) under the restriction of domain knowledge. When using p53-mediate DNA damage response network as illustration, we find more meaningful MDSs by WDNfinder.

The source code is implemented in python and publicly available together with relevant data on GitHub: https://github.com/dustincys/WDNfinder.

In this paper a method for the identification of simplified linear models for building structures is applied to the case when acceleration, rather than displacement, is measured. A frame from benchmark structural controller studies is simulated, and from the input-output data of these simulations, simplified models for the acceleration response of the frame are obtained that have far fewer degrees of freedom. One of these simplified models is used to design a controller, which is tested using an evaluation model from the benchmark controller studies and found to be effective.

The paper investigates the effectiveness of a smart base-isolation system for seismic response mitigation of extra-large liquified natural gas (LNG) storage tanks. The mathematical model of the base-isolated LNG tank with smart dampers, the magneto-rheological (MR) dampers, is presented. The governing equations of motion of the smart system are derived and solved by the classical transition matrix method in the time domain. The linear quadratic regulator (LQR) control scheme is employed to command MR dampers. The LNG tank system is analyzed under six artificial accelerograms, compatible with operational basis earthquake (OBE) and safe shutdown earthquake (SSE) response spectrum, generated using a method of a random set of phase angles with amplitudes obtained from power spectral density function. A time-delay compensation procedure based on the Taylor series expansion is applied to reduce the deterioration of control performance due to time delay. To investigate the effectiveness of smart base-isolation, the responses are compared with the fixed-base tank, base-isolated tank, and tank with passive MR damper. The results show that the smart base-isolation is effective in reducing the seismic response of extra-large LNG tanks, especially the displacement at the isolation level without much altering other responses. The passive MR damper is also found effective and showed fail-safe behavior even under the failure of the control algorithm. Moreover, the application of time-delay compensation using the Taylor series increased the performance and overall efficiency of the LNG tank system.

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.