Benchmark Problem for Response Control of Wind-Excited Tall Buildings

This paper presents an overview and problem definition of a benchmark problem for the response control of wind-excited tall buildings. The building considered is a 76-story 306 m concrete office tower proposed for the city of Melbourne, Australia. The building is slender with a height to width ratio of 7.3; hence, it is wind sensitive. Wind tunnel tests for such a 76-story building model have been conducted at the University of Sydney and the results of across-wind data are used in the present benchmark problem. Either active, semiactive, or passive control systems can be installed in the building to reduce the wind response, although only an active control sample problem has been worked out to illustrate the control design. In the case of active control systems, either an active tuned mass damper or an active mass driver can be installed on the top floor. In the case of passive or semiactive systems, such as viscous dampers, viscoelastic dampers, electrorheological, or magnetorheological dampers, etc., control devices can be installed in selected story units. Control constraints and evaluation criteria are presented for the design problem. A simulation program based on the linear quadratic Gaussian technique has been developed and made available for the comparison of the performance of various control strategies.     

Vibration Control of the Wind-Excited 76-Story Benchmark Building by Liquid Column Vibration Absorbers

A study has been undertaken on the effectiveness of using liquid column vibration absorbers (LCVAs), in the suppression of wind-induced motion of the 76-story benchmark building. Much work has been undertaken on the behavior of the LCVA on an experimental level and its benefits have been demonstrated for wind-induced vibration control on a full-scale communications tower in Sydney, Australia, with a further installation being made on the “One Wall Center Building” Vancouver, Canada. The behavior of the LCVA has also been investigated numerically by use of computational fluid dynamics, and its potential has been illustrated in controlling a five-story building model. In this study, the LCVA adopted is composed of four identical columns of water. Initially, the performance of the LCVA is assessed without the inclusion of additional damping enhancing mechanisms. Subsequently, the same LCVA is considered with the inclusion of orifice plates, allowing a direct comparison of the two strategies. In order to address the issue of robustness, the sensitivity of the LCVA (with and without orifice) to mistuning is examined by perturbing the structural stiffness of the building by +15% and ?15%, respectively. From this, an indication of the system performance under conditions of mistuning has been assessed. The performance of the adopted LCVA has also been compared to that of the sample tuned mass damper (TMD) control device. The overall response reductions of the LCVA are shown to be comparable to the TMD. Furthermore, it is shown that the LCVA has several inherent features that make it more attractive than the classical TMD.     

Active Control of Cross Wind Response of 76-Story Tall Building Using a Fuzzy Controller

This paper focuses on the benchmark problem application regarding the vibration control of tall buildings under cross wind excitation. The building under consideration is the 76-story, 306-m tall reinforced concrete office tower proposed for the city of Melbourne, Australia. The adopted control scheme consists of an active tuned mass damper (ATMD) where the control action is achieved by a fuzzy logic controller (FLC). The main advantage of the FLC is its inherent robustness and ability to handle any nonlinear behavior of the structure and the fact that its implementation does not require a mathematical model of the structure. This benchmark study is based on specified design constraints for the ATMD to be considered in the design of the proposed control scheme. The performance of the controller has been demonstrated through the uncertainty in stiffness (+15 and ?15% variation from initial stiffness) of the building. The results of the simulation show a good performance by the fuzzy controller for all cases tested. Also the results show that the fuzzy controller performance is similar to the linear quadratic Gaussian (LQG) controller, while possessing several advantages over the LQG controller.     

Modified Sliding Mode Control for Wind-Excited Benchmark Problem

Among promising control strategies, the sliding mode control is particularly robust with respect to structural uncertainty. In this paper, a modified sliding mode control (MSMC) strategy using dynamic output feedback is presented and demonstrated for the wind-excited benchmark building equipped with an ATMD (active tuned mass damper) control device. The main advantage of the MSMC presented is its ability to systematically modulate the control effort through the introduction of a prefilter prior to the control force. For practical implementation of a MSMC using acceleration measurements at strategic locations, a Kalman–Bucy filter type of observer is designed based on the augmented system. Hence the sliding surface design is composed of the observer state, and the modulation of control forces can be achieved by forming an optimization problem with a linear quadratic objective function. As shown by the simulation results of the wind-excited benchmark building, the modified sliding mode controller indeed has the capability of systematically modulating the control force. Moreover, the remarkable performance of the MSMC demonstrates that the strategy presented is suitable for the wind-excited tall buildings.     

Distributed Mass Damper System for Integrating Structural and Environmental Controls in Buildings

The writers recently proposed a new type of mass damper system to integrate structural and environmental control systems for buildings. External shading fins are used as mass dampers such that they can (1) control building energy consumption by adjusting the fins and, thus, the amount of sunlight entering the building; and (2) control structural movements by dissipating energy with the dampers during strong motions. Because shading fins are placed along the height of the building, the mass dampers are distributed along the building height instead of concentrated in one or a few locations like traditional tuned mass dampers (TMDs). The distributed mass damper (DMD) system is formulated and simulated for earthquake motions. Optimization is performed on damper parameters (i.e., masses, stiffness, and damping coefficients) of the passive DMD system to minimize structural responses. A near-optimal DMD system outperforms a single TMD system. The movable shading fins are also briefly discussed; they show a substantial savings in building energy consumption.     

Multiobjective Optimal Fuzzy Logic Control System for Response Control of Wind-Excited Tall Buildings

Performance of the structure includes both the safety as well as comfort level for the user. The safety of the structure mainly depends on the displacement response, while the comfort level of occupants depends on the acceleration response. In this paper, an approach for multiobjective optimal design of a fuzzy logic controller (FLC)-driven active tuned mass damper (ATMD) has been proposed. The evaluation criteria for both the acceleration and displacement responses have been used as the two objective functions for this multiobjective optimization problem. As a multiobjective optimization approach provides a set of Pareto-optimal solutions, the user is allowed to select an appropriate design for the specific performance requirement. The effectiveness and performance of the proposed FLC-driven ATMD has been investigated for the third-generation benchmark problem for the response control of wind-excited tall buildings. A multiobjective optimization version of the genetic algorithm has been used for obtaining the FLC and ATMD design parameters, as this approach is more effective in handling a discontinuous and nonconvex domain. Performance of the proposed control system has been found to be better than the sample controller given in the benchmark problem. The proposed controller is less sensitive than the sample controller for the variation in the stiffness of the structure.     

Protecting Base-Isolated Structures from Near-Field Ground Motion by Tuned Interaction Damper

This paper deals with the combined use of a low-damping base-isolation system and a semiactive control system referred to as a tuned interaction damper (TI damper). The TI damper generates friction-type forces (rigid-plastic behavior) through interactions between the primary isolated structure and an auxiliary structure. Because of its energy-dissipation nature, a base-isolated structure controlled by a TI damper is inherently stable, and as a semiactive control device, its operation requires only minimal external power. The efficacy of the proposed hybrid system is examined through a numerical simulation for a five-story scaled building subjected to near-field ground motions. A sensitivity analysis on the parameter dependence of the structural response on control force limit, stiffness ratio, and frequency ratio is presented. By tuning these parameters to optimal values, the performance of the base-isolated structure equipped with a TI damper can be enhanced. Based on the numerical simulation results, it is concluded that a TI damper is capable of suppressing the base drift of base-isolated structures subjected to near-field earthquake ground motions while maintaining the superstructure interstory drift and accelerations at small levels.     

Application of a Genetic Algorithm for Optimal Damper Distribution within the Nonlinear Seismic Benchmark Building

This paper presents a systematic method for identifying the optimal damper distribution to control the seismic response of a 20-story benchmark building. A genetic algorithm with integer representation was used to determine the damper locations. Both H2- and H∞-norms of the linear system transfer function were utilized as the objective functions. Moreover, frequency weighting was incorporated into the objective functions so that the genetic algorithm emphasized minimization of the response in the second mode of vibration instead of the dominant first mode. The results from numerical simulations of the nonlinear benchmark building show that, depending on the objective function used, the optimal damper locations can vary significantly. However, most of dampers tend to be concentrated in the lowermost and uppermost stories. In general, the damper configurations evaluated herein performed well in terms of reducing the seismic response of the benchmark building in comparison to the uncontrolled building.     

Seismic Energy Dissipation of Inelastic Structures with Tuned Mass Dampers

The energy transfer process of using a tuned mass damper (TMD) in improving the ability of inelastic structures to dissipate earthquake input energy is investigated. Inelastic structural behavior is modeled by using the force analogy method, which is the backbone of analytically characterizing the plastic energy dissipation in the structure. Numerical simulations are performed to study the energy responses of structures with and without TMD installed. The effectiveness of TMD in reducing energy responses is also studied by using plastic energy spectra for various structural yielding levels. Results show that the use of TMD enhances the ability of the structures to store larger amounts of energy inside the TMD that will be released at a later time in the form of damping energy when the response is not at a critical state, thereby increasing the damping energy dissipation while reducing the plastic energy dissipation. This reduction of plastic energy dissipation relates directly to the reduction of damage in the structure, and TMD is therefore concluded to be quite effective in protecting structures from suffering major damage during an earthquake. However, storing energy in the TMD is restricted if the structure becomes plastic at a small displacement level. In this case, the effectiveness of TMD diminishes, and the structural response becomes practically the same as those without TMD installed.     

振动筛隔振装置的设计研究

论述两种类型振动筛的振动特性及其隔振装置的设计方法。对于驱动系统中配备偏心装置的振动筛,为了减小动载荷的传递,可在振动筛与建筑物之间增设一个弹簧支承的辅助隔振装置进行隔振;对于采用反向旋转不平衡量驱动的振动筛,同样需要增设一个弹簧支承的辅助隔振装置进行隔振;当两种类型振动筛隔振装置的隔振基础块质量为振动筛质量的5-10倍时,才能获到较好的隔振效果。对于安装振动筛的建筑物不能承受隔振基础块之质量时,可考虑采用调谐质量减振器方案进行减振。     

Control Effect for 20-Story Benchmark Building Using Passive or Semiactive Device

In this paper, we study the control effect for a 20-story benchmark building and apply passive and semiactive control devices to the building. First, we take viscous damping walls as a passive control device which consists of two outer plates and one inner plate, facing each other with a small gap filled with viscous fluid. The damping force is related to the interstory velocity, temperature, and the shearing area. Next, we take a variable oil damper as a semiactive control device which can produce the control forces by little electrical power. We propose a damper model in which the damping coefficient changes according to the response of the damper and control forces calculated by the controller based on a linear quadratic Gaussian control theory. It is demonstrated from the results of some simulations that both passive device and semiactive device can effectively reduce the response of the structure in various earthquake motions.     

Optimal Vibration Absorber with Nonlinear Viscous Power Law Damping and White Noise Excitation

A tuned mass damper with a nonlinear power law viscous damper excited by white noise is considered. The system is analyzed by statistical linearization and stochastic simulation with the objective of minimizing the standard deviation of the response. It is shown that the optimal parameters for the tuned mass damper are unaffected by the magnitude of the structural damping in the linear case. However, in the nonlinear case the structural damping influences the equivalent parameters obtained by statistical linearization and thereby indirectly the optimal values for the damper parameters. Results from stochastic simulation show good agreement with results from statistical linearization in terms of the standard deviation of the response. It is shown that the optimal damping, which can be obtained by the passive device, is the same for the linear and nonlinear damper. However, for the nonlinear tuned mass damper the optimal parameters will depend on both structural damping and excitation intensity (or vibration amplitude). The results are presented in such a way that they can be used directly for the design of a tuned mass damper with damping governed by a nonlinear viscous power law.     

Performance of Tuned Liquid Dampers

This paper investigates the performance of unidirectional and bidirectional tuned liquid dampers (TLDs) under random excitation. The performance of the tuned liquid dampers is measured in terms of efficiency and robustness. A series of experimental tests are conducted on model scale structure-tuned liquid damper systems to evaluate their performance, which is then compared to that of the well known tuned mass damper. The effective damping is calculated for each test conducted and the efficiency and robustness are subsequently examined. The performance of a mistuned TLD is experimentally investigated to highlight the robustness of these passive dynamic vibration absorbers. A nonlinear numerical model is used to conduct an extensive parametric study on the performance of a tuned liquid damper. This study has resulted in the development of performance charts for a tuned liquid damper. These charts allow the efficiency of a tuned liquid damper to be examined for a number of varying parameters, which include the excitation amplitude, water depth, and building frequency. These charts are particularly useful for the initial design of a tuned liquid damper when the precise frequency of the structure is not known.     

Model Predictive Control of Wind-Excited Building: Benchmark Study

In this paper, a “third generation” benchmark problem that focuses on the control of wind excited response of a tall building, using the Model Predictive Control (MPC) scheme, is presented. A 76 story, 306 m tall concrete office tower proposed for the city of Melbourne, Australia, is being used to demonstrate the effectiveness of MPC. The MPC scheme is based on an explicit use of a prediction model of the system response to obtain the control actions by minimizing an objective function. Optimization objectives in MPC include minimization of the difference between the predicted and desired response trajectories, and the control effort subjected to prescribed constraints. By incorporating input/output hard constraints, the MPC scheme provides an optimal control force that satisfies the prescribed constraints.     

Identification of Natural Frequencies and Dampings of In Situ Tall Buildings Using Ambient Wind Vibration Data

An accurate prediction for the response of tall buildings subject to strong wind gusts or earthquakes requires the information of in situ dynamic properties of the building, including natural frequencies and damping ratios. This paper presents a method of identifying natural frequencies and damping ratios of in situ tall buildings using ambient wind vibration data. Our approach is based on the empirical mode decomposition (EMD) method, the random decrement technique (RDT), and the Hilbert–Huang transform. Our method requires only one acceleration sensor. The noisy measurement of the building acceleration is first processed through the EMD method to determine the response of each mode. Then, RDT is used to obtain the free vibration modal response. Finally, the Hilbert transform is applied to each free vibration modal response to identify natural frequencies and damping ratios of in situ tall buildings. The application of the proposed methodology is demonstrated in detail using simulated response data of a 76-story benchmark building polluted by noise. Both the along-wind and across-wind vibration measurements have been illustrated. Simulation results demonstrate that the accuracy of the proposed method in identifying natural frequencies and damping ratios is remarkable. The methodology proposed herein provides a new and effective tool for the parametric identification of in situ tall buildings.     

Damping of Cables by a Transverse Force

A general asymptotic format is presented for the effect on the modal vibrations of a transverse damper close to the end of a cable. Complete locking of the damper leads to an increase of the natural frequencies, and it is demonstrated that the maximum attainable damping is a certain fraction of the relative frequency increase, depending on the type of damping device. The asymptotic format only includes a real and a complex nondimensional parameter, and it is demonstrated how these parameters can be determined from the frequency increase by locking and from an energy balance on the undamped natural vibration modes. It is shown how the asymptotic format can incorporate sag of the cable, and specific results are presented for viscous damping, the effect of stiffness and mass, fractional viscous damping, and a nonlinear viscous damper. The relation of the stiffness component to active and semiactive damping is discussed.     

Controlling Wind Response through a Fuzzy Controller

The aim of this paper is to discuss the adoption of a fuzzy controller for the reference system proposed in the benchmark problem covering the wind response control of a tall building. The writers approach the problem by conceiving the fuzzy controller as receiving the input from two sensors and driving the single actuator which has been added, in the benchmark problem, to the initially passive control device. The numerical investigation requires that the actual behavior of a fuzzy chip is simulated and this aspect is implemented in the paper.     

Seismic Response Control of Building Structures with Superelastic Shape Memory Alloy Wire Dampers

This paper presents a simulation-based benchmark control study in which shape memory alloy (SMA) wire dampers are utilized to control the seismic response of a three-story nonlinear steel frame building. The SMA wire damper uses superelastic Nitinol wires for energy dissipation because of its high fatigue life and large recoverable strain. An analytical model which considers the training effect of SMA wires is used to describe the stress-strain relationship of superelastic SMA wires. The performance of SMA wire dampers is investigated in the framework of the third-generation benchmark problem on structural control. A comparative study of the seismic response control performance of SMA wire dampers with either unprestrained or prestrained SMA wires was also conducted. The results of this simulation-based benchmark control study show that SMA wire dampers, as a passive structure control measure, can effectively reduce the seismic responses of the three-story nonlinear benchmark building structure and has the potential to withstand several design earthquakes without the need for repair.     

Generalized Linear Quadratic Gaussian Techniques for the Wind Benchmark Problem

This paper presents a comprehensive study of the stage-3 benchmark problem for response control of wind-excited tall buildings based on the linear quadratic gaussian (LQG) approach, and on its generalization, the k-cost-cumulant control method. For control design, the original nodal building model is first transformed into balanced modal space. The Hankel singular values (HSVs) and the power spectral density of the wind disturbances are calculated; and, based on them, a reduced-order model is derived by keeping the first six low-frequency modes. A balanced LQG (BLQG) controller is then determined by adopting the HSVs as a basis to choose the design weights. The main results of the paper are that the BLQG control design is able to come within 5–10% of the performance of the sample LQG controller supplied with the benchmark, but with control actions on the order of one-third less than the sample LQG, and with stability improvement features of a substantial nature over the range of stiffness perturbations specified in the benchmark. Finally, if the low authority BLQG controller is regarded as a one-cost-cumulant design, then with the appropriate use of the second-cost cumulant, the latter methodology is able to demonstrate how higher-authority controllers can give certain improvements in performance, but at the expense of significant investment in control action.     

Tuned Mass Damper Design for Optimally Minimizing Fatigue Damage

Traditionally the usage of a tuned mass damper (TMD) is to improve the survivability of the primary structure under an extraordinary loading environment while the design loading condition is often described by a harmonic function, or sometimes by a stationary random process that can be fully characterized by a power spectral density (PSD) function. In contrast, this paper considers the environmental loading to be a long-term nonstationary stochastic process characterized by a probabilistic PSD function. One engineering motivation to design a TMD under a long-term random loading condition is for prolonging the fatigue life of the primary structure. The primary contribution of this study is to provide the theoretical framework for designing a TMD that can optimally minimize structural fatigue damage.