• Structural Engineering and Mechanics
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• v.15 no.6
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• pp.669-683
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• 2003

The stochastic optimal nonlinear control of coupled adjacent building structures is studied based on the stochastic dynamical programming principle and the stochastic averaging method. The coupled structures with control devices under random seismic excitation are first condensed to form a reduced-order structural model for the control analysis. The stochastic averaging method is applied to the reduced model to yield stochastic differential equations for structural modal energies as controlled diffusion processes. Then a dynamical programming equation for the energy processes is established based on the stochastic dynamical programming principle, and solved to determine the optimal nonlinear control law. The seismic response mitigation of the coupled structures is achieved through the structural energy control and the dimension of the optimal control problem is reduced. The seismic excitation spectrum is taken into account according to the stochastic dynamical programming principle. Finally, the nonlinear controlled structural response is predicted by using the stochastic averaging method and compared with the uncontrolled structural response to evaluate the control efficacy. Numerical results are given to demonstrate the response mitigation capabilities of the proposed stochastic optimal control method for coupled adjacent building structures.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.103-111
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• 2009

Multi-climbing hydraulic robots are used to lift construction factory (CF) synchronously for applications in the automation of a high-rise building construction. In this study, synchronous motion controller is proposed for the hydraulic robots, whose strategy is not only to make each robot follow the reference path basically by sliding-mode control, but also to synchronize motions of two adjacent cent robots consecutively by cross-coupled control technique. Simulations are performed by using SIMULINK for a system similar to a practical application that includes unbalance in CF and wind disturbance. The results show that the proposed controller significantly reduces synchronous errors, compared to the individual controller for each hydraulic robot.

• Wind and Structures
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• v.3 no.3
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• pp.193-207
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• 2000

The possible application of a spatially placed passive tuned liquid column damper system for suppressing coupled lateral-torsional responses of tall buildings is investigated in this paper. The wind loads acting on rectangular tall buildings are analytically expressed as 3-D stochastic model. Meanwhile, the 3-D responses of tall buildings may be coupled due to eccentricities between the stiffness and mass centers of the buildings. In these cases, torsional responses of the buildings are rather larger, and a TLCD system composed of several TLCD located near the sides of the buildings is more effective than the same TLCD placed at the building center in reducing both translational and torsional responses of the buildings. In this paper, extensive analytical and numerical work has been done to present the calculation method and optimize the parameters of such TLCD systems. The numerical examples show that the spatially placed TLCD system can reduce coupled along-wind, across-wind and torsional responses significantly with a fairly small mass ratio.

• Structural Engineering and Mechanics
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• v.62 no.2
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• pp.197-208
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• 2017

Among various retrofitting strategies, use of semi-active control for retrofitting a building structure has gained momentum in recent years. One of the techniques for such retrofitting is to connect a weaker building to an adjacent stronger building by semi-active devices, so that performances of a weaker building are significantly improved for seismic forces. In this paper, a ten storey weaker building is connected to an adjacent stronger building using magneto-rheological (MR) dampers, for primarily improving the performance of the weaker building in terms of displacement, drift and base shear. For this, a fuzzy logic controller is specifically developed by fuzzyfying the responses of the coupled system. The performance of the control strategy is compared with the passive-on and passive-off controls. Pounding Mitigation between the two buildings is also investigated using all three control strategies. The results show that there exists a fundamental frequency ratio between the two buildings for which maximum control of the weaker building response takes place with no penalty on the stronger building. There exists also a fundamental frequency ratio where control of the weaker building response is achieved at the expense of the amplification of the stronger building. However, coupling strategy always improves the possibility of pounding mitigation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.3
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• pp.50-64
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• 2011

In this paper, a DC-coupled photovoltaic (PV), fuel cell (FC) and ultracapacitor hybrid power system is studied for building microgrid. In this proposed system, the PV system provides electric energy to the electrolyzer to produce hydrogen for future use and transfer to the load side, if possible. Whenever the PV system cannot completely meet load demands, the FC system provides power to meet the remaining load. The main weak point of the FC system is slow dynamics, because the power slope is limited to prevent fuel starvation problems, improve performance and increase lifetime. A power management and control algorithm is proposed for the hybrid power system by taking into account the characteristics of each power source. The main works of this paper are hybridization of alternate energy sources with FC systems using long and short storage strategies to build an autonomous system with pragmatic design, and a dynamic model proposed for a PV/FC/UC bank hybrid power generation system. A simulation model for the hybrid power system has been developed using Matlab/Simulink, SimPowerSystems and Matlab/Stateflow. The system performance under the different scenarios has been verified by carrying out simulation studies using a practical load demand profile, hybrid power management and control, and real weather data.

• Structural Engineering and Mechanics
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• v.36 no.2
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• pp.181-195
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• 2010

Coupled building control is a viable method to protect tall buildings from seismic excitation. In this study, the semi-active control of a building complex is investigated for mitigating seismic responses. The building complex is formed of one main building and one podium structure connected through Magneto-Rheological (MR) Dampers and Tuned Mass Damper. The conventional semi-active control techniques require a primary controller as a reference to determine the desired control force, and modulate the input voltage of the MR damper by comparing the desired control force. The fuzzy logic directly determines the input voltage of an MR damper from the response of the MR damper. The control performance of the proposed fuzzy control technique for the MR damper is evaluated for the control problem of a seismically-excited building complex. In this paper, a building complex that include a 14-story main building and an 8-story podium structure is applied as a numerical example to demonstrate the effectiveness of semi-active control with Magneto-Rheological dampers and its comparison with the passive control with the Tuned Mass Damper and two uncoupled buildings and hybrid semi-active control including the Tuned Mass Damper and Magneto-Rheological dampers while they are subject to the earthquake excitation. The numerical results show that semi-active control and hybrid semi-active control can significantly mitigate the seismic responses of both buildings, such as displacement and shear force responses, and fuzzy control technique can effectively mitigate the seismic response of the building complex.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.219-224
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• 2016

The vibration control performance of a semi-active damper connected to adjacent buildings subjected to seismic loads was investigated. The MR damper was used as a semi-active control device. A fuzzy logic control algorithm was used for effective control of the adjacent buildings connected to the MR damper. In the buildings control coupled with a MR damper, the response reduction of one building results in an increase in the response in another building. Because of these conflict characteristics, multi-objective optimization is required. Therefore, a fuzzy logic control algorithm for the control of a MR damper was optimized using a multi-objective genetic algorithm. Based on numerical analyses, the semi-active fuzzy control of MR damper for adjacent coupled buildings can provide good control performance.

• Wind and Structures
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• v.36 no.2
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• pp.91-103
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• 2023

Tuned liquid dampers (TLDs) are increasingly being used as efficient dynamic vibration absorbers to mitigate wind-induced vibration in super high-rise buildings. However, the damping characteristics of screens and the control effectiveness of actual structures must be investigated to improve the reliability of TLDs in engineering applications. In this study, a numerical TLD model is developed using computational fluid dynamics (CFD) and a simulation method for achieving the coupled vibration of the structure and TLD is proposed. The numerical results are verified using shaking table tests, and the effects of the solidity ratio and screen position on the TLD damping ratios are investigated. The TLD control effectiveness is obtained by simulating the wind-induced vibration response of a full-scale structure-TLD system to determine the optimal screen solidity ratio. The effects of the structural frequency, damping ratio, and wind load amplitude on the TLD performance are further analyzed. The TLD damping ratio increases nonlinearly with the solidity ratio, and it increases with the screens towards the tank center and then decreases slightly owing to the hydrodynamic interaction between screens. Full-scale coupled simulations demonstrated that the optimal TLD control effectiveness was achieved when the solidity ratio was 0.46. In addition, structural frequency shifts can significantly weaken the TLD performance. The control effectiveness decreases with an increase in the structural damping ratio, and is insensitive to the wind load amplitude within a certain range, implying that the TLD has a stable damping performance over a range of wind speed variations.

• Structural Engineering and Mechanics
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• v.22 no.1
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• pp.85-105
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• 2006

Control of structural response due to seismic excitation in a manner of coupling adjacent buildings has been actively developed, and most attention focused on those buildings of similar height. However, with the rapid development of some modern cities, multi-story buildings constructed with an auxiliary low-rise podium structure to provide extra functions to the complex become a growing construction scheme. Being inspired by the positively examined coupling control approach for buildings with similar height, this paper aims to provide a comprehensive analytical study on control effectiveness of using friction dampers to link the two buildings with significant height difference to supplement the recent experimental investigation carried out by the writers. The analytical model of a coupled building system is first developed with passive friction dampers being modeled as Coulomb friction. To highlight potential advantage of coupling the main building and podium structure with control devices that provide a lower degree of coupling, the inherent demerit of rigid-coupled configuration is then evaluated. Extensive parametric studies are finally performed. The concerned parameters influencing the design of optimal friction force and control efficiency include variety of earthquake excitation and differences in floor mass, story number as well as number of dampers installed between the two buildings. In general, the feasibility of interaction control approach applied to the complex structure for vibration reduction due to seismic excitation is supported by positive results.

• Wind and Structures
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• v.12 no.4
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• pp.313-332
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• 2009

This paper numerically and experimentally investigates the control performance of the active mass damper (AMD) systems in a 26-story high-rise building in use. This is the first full-scale application of the AMD system for suppressing the wind-induced vibration of a building structure in Korea. In addition, the AMD system was installed on top of the building already in use, which may be the world's first implementation case. In order to simultaneously mitigate the transverse-torsional coupled vibration of the building, two AMD systems were applied. Moreover, the H-infinity control algorithm has been developed to utilize the maximum capacity of the AMD system. From the results of numerical simulation using the wind load obtained from the wind tunnel tests, it was found that the maximum acceleration responses of the building were reduced significantly. Moreover, the control performance of the installed AMD system was examined by carrying out the free and forced vibration tests. The acceleration responses on top of the building in the controlled case measured under strong wind loads were compared with those in the uncontrolled case numerically simulated by using the wind load deduced from the measured data and a structural model of the building. It is demonstrated that the AMD system shows good control performance in reducing the building accelerations.