Vibrations In Civil Structures Research Articles

Calibration of Viscous Damping–Stiffness Control Force in Active and Semi-Active Tuned Mass Dampers for Reduction of Harmonic Vibrations

Tuned mass dampers (TMDs) are commonly used to mitigate vibrations in civil structures. There is a growing demand for new solutions that offer similar effectiveness as TMDs but with reduced mass. In this context, this paper investigates active (ATMD) and semi-active (STMD) tuned mass dampers with relative displacement and velocity feedback. The control force of the ATMD is assumed to be the sum of viscous damping and either positive or negative stiffness forces. This control force is calibrated for a specific parameter K such that the effectiveness of the ATMD in reducing harmonic vibrations matches that of the TMD with K times larger mass. The optimal calibration is derived based on the mathematical reformulation of an existing optimal acceleration feedback control algorithm. The control approach for the ATMD is then applied to the STMD. Subsequently, the sub-optimal STMD is analyzed, with a focus on its limitations arising from the clipping of active forces. Finally, the paper presents a calibration of the STMD using a numerical optimization method. It is demonstrated that the maximum achievable performance of the numerically optimized STMD matches that of the TMD with three times larger mass.

Passive vibration control in a civil structure: Experimental results

The problem of vibrations in civil structures is common; nevertheless, its negative effects can be significantly reduced using structural control methods with intention of maintaining structural welfare as much as possible. This work deals with the study of structural vibration control in a model of a civil-like structure, which consists of three-level building with a tuned mass damper implemented as a passive vibration absorber, mounted on the top of the structure, to attenuate the harmonic vibrations provided by an electromagnetic actuator connected at the base of the primary system. The action of the tuned mass damper is evaluated from an energy approach. The dissipation of energy in the overall system is conducted in an experimental way, where the passive control technique is designed to minimize the undesirable forced dynamic response of the main structure via the tuned mass damper. Experimental results are provided to show the effective performance of the proposed passive vibration absorption scheme to suppress resonant frequency harmonic excitations disturbing the primary system, evaluating the performance energy and contribution of the dissipative device for the energy release in the overall system.

Nonlinear optimal control for reducing vibrations in civil structures using smart devices

The frequently excessive vibrations presented in civil structures during seismic events or service conditions may result in users\' discomfort, or worst, in structures failure, producing economic and even human casualties. This work contributes in proposing the synthesis of a nonlinear optimal control strategy for semiactive structural control, with the main characteristic that the synthesis considers both the structure model and the semiactive actuator nonlinear dynamics, which produces a nonlinear system that requires a nonlinear controller design. The aim is to reduce the unwanted vibrations in the response of civil structures, by means of intelligent fluid semiactive actuator such as the Magnetorheological Damper (MRD), which is a device with a low level of power consumption. The civil structures for which the proposed control methodology can be applied are those admitting a state-dependent coefficient factorized representation model, such as buildings, bridges, among others. A scaled model of a three storey building is analyzed as a case study, whose dynamical response involves displacement, velocity and acceleration of each one of the storeys, subjected to the North-South component of the September 19th., 2017, Puebla-Morelos (7.1M), Mexico earthquake. The investigation rests on comparing the structural response over time for two different conditions: with no control device installed and with one MRD installed between the first floor and the ground, where a nonlinear optimal signal for the MRD input voltage is determined. Simulation results are presented to show the effectiveness of the proposed controller for reducing the building\'s dynamical response.

Performance of accelerated oscillator dampers under seismic loading

Structure control techniques have been used to control vibrations in civil structures from natural and other types of hazards for many years. However, it is difficult to achieve effective reduction...

Active vibration control design using the Coral Reefs Optimization with Substrate Layer algorithm

Active vibration control (AVC) via inertial-mass actuators is a viable technique to mitigate human-induced vibrations in civil structures. A multi-input multi-output (MIMO) AVC has been previously proposed in the literature to simultaneously find the sensor/actuator pairs’ optimal placements and tune the control gains. However, the method involved local gradient-based methods, which is not affordable when the number of possible locations of actuators is large. In this case, the computation time to obtain a local solution may be huge and unaffordable, which limits the number of test points and/or actuators/sensors considered. This paper proposes an alternative approach based on a recently proposed meta-heuristic, the Coral Reefs Optimization (CRO) algorithm. More concretely, an enhanced version of the CRO is considered, the Coral Reefs Optimization with Substrate Layer (CRO-SL). The CRO-SL is a competitive co-evolution algorithm in which different exploration procedures are jointly evolved within a single population of potential solutions to the problem. The proposed algorithm is thus able to promote competition among different search methods to solve hard optimization problems. In terms of structural design, this work provides an important step to improve the applicability of AVC systems to real complex structures (with a large number of vibration modes and/or with a large number of test points) by achieving global optimum designs with affordable computation time. A finite element model of a real complex floor structure is used to illustrate the contributions of this paper.

Modeling and Validation of a Passive Resettable Stiffness Damper

AbstractThe resetting semiactive stiffness damper (RSASD) has been shown to be effective at controlling vibrations in civil structures in the presence of near-field earthquakes. Although it has the advantages of being mechanically simple and relatively inexpensive, the RSASD requires a multicomponent feedback control system consisting of sensors, a microcontroller, a servo valve, and a battery to operate, rendering it less reliable during a seismic event. In the present work, the resetting passive stiffness damper (RPSD) is presented as an improvement to the RSASD, whereby the RSASD feedback control system is replaced by a novel mechanism to achieve resetting of the damper force. The results of laboratory studies on a small-scale RPSD demonstrate that the resetting mechanism performs as proposed. Results of numerical simulations performed for a five-story base-isolated building subject to four benchmark earthquakes indicate that the RPSD is capable of a similar control performance as the RSASD. Furthermor...

Equivalent-input-disturbance approach to active structural control for seismically excited buildings

A new method of active structural control, which suppresses vibrations in civil structures due to seismic shocks, has been developed. It is based on the equivalent-input-disturbance (EID) approach, which estimates the effect of a seismic shock and produces an equivalent control signal on the control input channel to compensate for it. A system designed by this method can be viewed as a conventional state-feedback control system with an EID estimator plugged in. Unlike conventional control systems, this one has two degrees of freedom, which yields better control performance. Simulations on a model of a ten-degree-of-freedom building demonstrated the validity of the method. In addition, the effect of the parameters of the low-pass filter in the EID estimator on the vibration suppression performance was examined. A comparison revealed that this method is superior to a linear-quadratic regulator and sliding-mode control.

A ModifiedD-KIteration Approach for the Decentralizedℋ∞Control of Civil Structures with Parametric Uncertainties

This paper presents a robust decentralizedℋ∞controller design method to suppress the vibration of civil structures with the consideration of parametric uncertainties. The decentralizedℋ∞controller design is motivated by the double homotopy approach, which approximates the bilinear matrix inequality (BMI) derived from bounded real lemma to linear matrix inequality (LMI), and gradually deforms a centralized controller to a decentralized controller. The centralizedℋ∞controller can be designed for the civil structures with the parametric uncertainties throughD-Kiteration method inμsynthesis, which can consider the diagonal block pattern of the uncertain matrix. This paper combines the double homotopy approach andD-Kiteration method to design the robust decentralizedℋ∞controller for the civil structures with parametric uncertainties. The proposed method is validated numerically with a four-story building example.

Discrete direct adaptive ELM controller for active vibration control of nonlinear base isolation buildings

Hybridization of base isolation and active control is a promising alternative to suppress the seismic vibrations in civil structures. The base-isolation system introduces hysteretic/frictional nonlinearity into the structure and hence there is a need to develop a nonlinear adaptive control approach to subdue the vibrations. In this paper, the authors propose discrete direct adaptive ELM controller for active control of nonlinear base isolated building, subjected to a set of near-fault earthquakes. A single hidden layer neural controller with random selection of input weights compensates the nonlinearity and provides desired vibration suppression. The neural controller is based on the extreme learning machine algorithm with random input weight selection and output weights are updated using Lyapunov like adaptation rule. The proposed discrete adaptive control law provides necessary stability and vibration suppression in nonlinear base isolated building. Simulation studies have been carried out using the full-scale three dimensional benchmark eight-storey building comprising hysteretic lead-rubber base-isolation. One earthquake record and perturbed model is used to train the controller offline. The offline trained controller is adapted online using the actual full-scale model for a wide range of near-fault earthquakes. The results clearly show that the proposed controller suppresses the vibration significantly without increasing superstructure responses. The comprehensive performance measures are compared with existing results reported in the literature.

Vibration Control on Smart Civil Structures: A Review

Smart civil structures are capable of partially compensating the undesirable effects due to external perturbations; they sense and react to the environment in a predictable and desirable form through the integration of several elements, such as sensors, actuators, signal processors, and power sources, working with control strategies. This article will focus on reviewing the main control techniques applied to suppress vibrations in civil structures using smart materials, remarking on the advantages and disadvantages of smart actuators and control strategies tendencies in smart civil structures.

Tunable Energy Harvesting from Ambient Vibrations in Civil Structures

AbstractEnergy harvesting from ambient vibrations in civil structures provides a potential permanent power source for sensor networks used in structural health monitoring. These structures exhibit a narrow, natural frequency-response range, which is generally one to two orders of magnitude lower than the operating frequency spectrum of most piezoelectric-scavenging devices. This considerably limits the levels of harvestable power and thus hinders the implementation of advanced sensing functionalities. In this paper, the improvement of the energy-harvesting characteristics of a bimorph cantilever lead zirconate titanate (PZT) piezoelectric beam is studied. The application of a variable prestress-loading condition is used as a solution to modify the system’s properties. A generalized model that takes into account all the vibration-mode shapes of the beam and the back-coupling effect is derived using the Hamiltonian principle. The model describes the effect of the prestress parameters on the harvestable ener...

Control of a Civil Structure Using an Electric Machine with Semiactive Capability

This paper concerns the implementation of a brushless DC machine as a force actuator, for use in suppressing vibrations in civil structures. The machine has the dual capability of operation as an active as well as semiactive device. It operates semiactively by using the machine as a generator to convert mechanical energy to electrical energy which is then dissipated. The electrical network uses electronic switching to control the power flow from the machine. With the machine shaft connected to a gear reducer and ballscrew mechanism, the result is a device that resembles a linear damper with a controllable damping coefficient. The only external electrical power required is that which is needed to support the control system intelligence and to control the transistors, enabling the device to be operated on battery power. As an example of an application of such an actuator, simulations are performed in which the semiactive device is used to control a three-story structural model, with acceleration feedback control. The structural control system design approach is the well-established “clipped-optimal” method. Results suggest that this actuator is effective in simultaneously suppressing the interstory drifts and the absolute accelerations of the structure. A comparison is made to a similar configuration using a magnetorheological damper as the semiactive force device.