On the efficiency of semi‐active smart structures: self‐regulating MR dampers control system for tall buildings

Many severe dynamical loadings such as earthquakes and strong winds may subject to structural systems during their lifetime and lead to changes in structural characteristics. Hence, employing an adaptive control strategy that can deal with these alterations compound with design of the structural elements would undoubtedly be the most effective alternative design for the old‐fashioned design methods, which are relatively inefficient in response to these unforeseen conditions. In the current study, benefits of employing the modern control systems for design of tall buildings in comparison with the uncontrolled traditionally designed structures are thoroughly investigated. To contract the vibrational responses due to seismic excitations, the innovative direct‐modulating semi‐active controller is designed for magneto‐rheological dampers, which are installed in an 11‐storey sample building converting it to a smart structure. Copyright © 2013 John Wiley & Sons, Ltd.     

Semi‐active algorithm for energy‐based predictive structural control using tuned mass dampers

A novel semi‐active control algorithm is developed and numerically evaluated for the suppression of undesirable structural vibrations. The mechanical energy of the vibrating structure is considered as the primary variable influencing the control action. This intuitive strategy is proposed to realize improved control of structural vibrations. The numerical study conducted reveals that the proposed energy‐based predictive (EBP) algorithm can be implemented on vibration control applications. The energy imparted to the structure is also reduced due to the proposed algorithm. The influence of the parameters of the proposed semi‐active tuned mass damper is studied. Further, the application of the proposed strategy on a realistic structure is numerically demonstrated by implementing the algorithm for the wind response control of a 76‐story benchmark building. The results show that the EBP algorithm is a competitive semi‐active strategy. The robustness of the strategy is also evaluated considering uncertainties in the properties of the benchmark building.     

Seismic response control of base‐isolated buildings using multiple tuned mass dampers

Seismic response of a base‐isolated building equipped with single tuned mass damper (STMD), multiple tuned mass dampers (MTMDs), and distributed multiple tuned mass dampers (d‐MTMDs) under real earthquake ground motions is investigated. Numerical study is carried out using analytical models of five‐, 10‐, and 15‐storey base‐isolated buildings equipped with the STMD, MTMDs, and d‐MTMDs. The buildings are modeled as shear‐type structure with a lateral degree of freedom at each floor level, and the buildings are isolated using the laminated rubber bearing, lead‐core rubber bearing, friction pendulum system, and resilient‐friction base isolator. The coupled differential equation of motion for the buildings are derived and solved in the incremental form using Newmark's step‐by‐step method of integration. From the numerical study conducted, it is concluded that installing a tuned mass damper at each floor level of a base‐isolated building reduces the structural response in terms of top floor acceleration and bearing displacement. It is found that installing the MTMDs and d‐MTMDs are significantly beneficial in reducing top floor acceleration as compared with the STMD. Further, almost comparable reduction in the bearing displacement could be obtained by installing the STMD, MTMDs at top, and d‐MTMDs in the base‐isolated buildings. The d‐MTMDs are more beneficial as compared with the STMD and MTMDs as otherwise huge controller mass can now be divided and distributed on different floor levels.     

Investigations concerning seismic response control of self-anchored suspension bridge with MR dampers

To mitigate the seismic response of self-anchored suspension bridges, equations of motion governing the coupled system of bridge- magneto-rheological (MR) dampers subject to seismic excitation are formulated by employing the phenomenological model of MR dampers. A corresponding computer program is developed and employed for studying the seismic response control of a self-anchored suspension bridge with a main span of 350 m. The effect of variable current and number of dampers on seismic response control is investigated. The numerical results indicate the longitudinal displacement of the tower top and bridge girder decrease with the increase in input current and number of MR dampers attached longitudinally at the tower-girder connections, and the internal forces of the tower are effectively attenuated as well. It appears that small electronic current (0.5 A in this study) may sufficiently attenuate the seismic responses for practical engineering applications.     

Investigations concerning seismic response control of self-anchored suspension bridge with MR dampers

To mitigate the seismic response of self-anchored suspension bridges, equations of motion governing the coupled system of bridge-magneto-rheological (MR) dampers subject to seismic excitation are formulated by employing the phenomenological model of MR dampers. A corresponding computer program is developed and employed for studying the seismic response control of a self-anchored suspension bridge with a main span of 350 m. The effect of variable current and number of dampers on seismic response control is investigated. The numerical results indicate the longitudinal displacement of the tower top and bridge girder decrease with the increase in input current and number of MR dampers attached longitudinally at the tower-girder connections, and the internal forces of the tower are effectively attenuated as well. It appears that small electronic current (0.5 A in this study) may sufficiently attenuate the seismic responses for practical engineering applications. __________ Translated from China Civil Engineering Journal, 2006, 39(11): 84–89 [译自: 土木工程学报]     

Semi‐active predictive control of non‐linear structures with controlled stiffness devices and friction dampers

A predictive semi‐active control system used to improve the response of non‐linear multistorey structures to earthquakes is presented. A system of controlled stiffness devices (CSD) and friction dampers (FD) is studied. The system combines the forces produced by the semi‐active FD and additional stiffness supplied by the CSD in order to obtain an optimal structural response. A predictive algorithm is used to overcome the time delay problem in the control system. The control forces in the FD are calculated at every time step by applying the instantaneous optimum control law according to the structural behaviour predicted for the next time step at each storey level of the structure. The proposed system can be efficiently used for structural control because the forces developed in it are independent of the structure's displacements or velocities. Its efficiency is demonstrated by a numerical simulation of a seven‐storey building subjected to various seismic excitations. The simulation shows that the behaviour of a structure with the proposed control system is significantly improved compared to an uncontrolled one, or controlled by friction dampers or by semi‐active controlled stiffness devices only. The structural response with a predictive controlled system is similar to that with an instantaneous one. Copyright © 2004 John Wiley & Sons, Ltd.     

地铁上盖多塔楼隔震与减振设计研究

考虑到转换层刚度突变对结构地震响应的不利影响以及地铁振动带来的舒适度问题,采用厚肉橡胶支座对上海莘庄地铁上盖多塔结构进行了层间隔震设计研究。采用时程分析方法,分别对采用刚性转换层结构方案和隔震层转换方案进行了计算。通过设防地震作用下刚性方案和隔震方案的结构响应对比,验证了隔震效果。通过罕遇地震作用下隔震层转换方案支座最大位移和拉应力验算,验证了隔震结构在罕遇地震作用下的安全性能。并根据相关规定,验算了结构抗风和微振动的性能。计算结果表明,经过合理的设计,采用厚肉橡胶支座的隔震既能达到普通橡胶支座隔震相同的效果,又没有结构的倾覆摇摆问题,为上盖塔楼结构的抗震与减振设计提供了一种新思路。     

自锚式悬索桥磁流变阻尼器减震控制研究

为了减小自锚式悬索桥的地震响应,基于桥梁结构地震动力方程及磁流变阻尼器力学模型,建立桥梁结构—磁流变阻尼器减震系统并将其程序化,对某主跨350 m的独塔自锚式悬索桥进行减震控制研究,讨论了磁流变阻尼器输入电流、数目及安装位置对减震效果的影响。研究结果表明:采用磁流变阻尼器能够有效地减小自锚式悬索桥的纵向地震响应;随安装在塔梁之间顺桥向的磁流变阻尼器输入电流的增大及数目的增加,塔顶和主梁的纵向位移逐渐减小,结构的内力响应也得到有效控制;将全部磁流变阻尼器安装在塔梁之间顺桥向时减震效果最佳。     

Seismic response control of asymmetric buildings using tuned mass dampers

The aim of the present study is to investigate the efficiency of the torsional tuned mass dampers (T‐TMDs) in response control of asymmetric buildings under bidirectional earthquake ground excitations. The efficiency of the T‐TMDs is compared with bidirectional tuned mass dampers (BTMDs). The T‐TMDs are oriented to the rotation of the structures about vertical axis with a single torsional mass attached to spring–dashpot elements, whereas the BTMD connects a single mass to two orthogonal sets of spring–dashpot elements oriented to principal axes of the building. The buildings are idealized three‐dimensional models with two translational and one torsional degrees of freedom for each floor. Three different configurations (cruciform‐shaped, L‐shaped, and T‐shaped) of multistory buildings are considered. The 5‐, 15‐, and 20‐story buildings with and without the tuned mass damper schemes are subjected to bidirectional earthquake ground excitation. In order to evaluate the effectiveness of the T‐TMDs and BTMD, the rotation, displacement, acceleration, and base shear force responses are computed. Parametric studies are conducted for all the configurations installed with the T‐TMDs and BTMD by varying their mass ratio, damping ratio, and ground motions. It is concluded that the T‐TMDs are more effective in mitigating the torsional response of asymmetric buildings as compared with the BTMD.     

Experimental study of seismic response of buildings with supplemental fluid dampers

This paper presents the results of an experimental study of the seismic response of buildings with supplemental fluid damping devices. These devices operate on the principle of fluid flow through orifices specially shaped so as to produce damping forces proportional to the velocity, i.e. the devices operate as linear viscous dampers. The experimental results demonstrate that the addition of fluid dampers to the tested steel model structure resulted in reductions of interstory drifts, floor accelerations and story shear forces by factors of two to three in comparison with the response of the same structure without the dampers.     

Semi‐active control for eccentric structures with MR damper based on hybrid intelligent algorithm

In this paper, an application of the hybrid intelligent control algorithm to semi‐active control of the magnetorheological (MR) damper is presented for engineering structures. The control signal is optimized directly by the µGA approach to obtain the numerical relation between the control signal and the system output. This relation is then stored in the weight value of a trained artificial neural network, which can be available for another structure subjected to other seismic inputs. The results of a numerical example indicate that the semi‐active control of the MR damper based on the hybrid algorithm can efficiently reduce the structural responses induced by an earthquake. Copyright © 2007 John Wiley & Sons, Ltd.     

Approximate method of estimating seismic performance of high‐rise buildings with oil‐dampers

When subjected to long‐period ground motions, many existing high‐rise buildings constructed on plains with soft, deep sediment layers experience severe lateral deflection, caused by the resonance between the long‐period natural frequency of the building and the long‐period ground motions, even if they are far from the epicenter. This was the case for a number of buildings in Tokyo, Nagoya, and Osaka affected by the ground motions produced by the 2011 off the Pacific coast of Tohoku earthquake in Japan. Oil‐dampers are commonly used to improve the seismic performance of existing high‐rise buildings subjected to long‐period ground motion. This paper proposes a simple but accurate analytical method of predicting the seismic performance of high‐rise buildings retrofitted with oil‐dampers installed inside and/or outside of the frames. The method extends the authors' previous one‐dimensional theory to a more general method that is applicable to buildings with internal and external oil‐dampers installed in an arbitrary story. The accuracy of the proposed method is demonstrated through numerical calculations using a model of a high‐rise building with and without internal and external oil‐dampers. The proposed method is effective in the preliminary stages of improving the seismic performance of high‐rise buildings.     

Coupled‐two‐beam discrete model for dynamic analysis of tall buildings with tuned mass dampers including soil–structure interaction

An equivalent coupled‐two‐beam discrete model is developed for time‐domain dynamic analysis of high‐rise buildings with flexible base and carrying any number of tuned mass dampers (TMDs). The equivalent model consists of a flexural cantilever beam and a shear cantilever beam connected in parallel by a finite number of axially rigid members that allows the consideration of intermediate modes of lateral deformation. The equivalent model is applied to a shear wall–frame building located in the Valley of Mexico, where the effects of soil–structure interaction (SSI) are important. The effects of SSI and TMDs on the dynamic properties of the shear wall–frame building are shown considering four types of soil (hard rock, dense soil, stiff soil, and soft soil) and two passive damping systems: a single TMD on its top (1‐TMD) and five uniformly distributed TMDs (5‐TMD). The results showed a great effectiveness of the TMDs to reduce the lateral seismic response and along‐wind response of the shear wall–frame building for all types of soils. Generally speaking, the dynamic response increases as the flexibility of the foundation increases.     

Wind‐induced vibration control of tall buildings using hybrid buckling‐restrained braces

A buckling‐restrained brace (BRB) is a system with excellent earthquake‐proof performance, but it does not dissipate energies caused by the load from weak earthquakes or winds. A hybrid BRB (H‐BRB), which improved the performance of the BRB, is a type of composite damper system consisting of a BRB and a viscoelastic damper. To explain the wind‐induced vibration control performance of H‐BRB, a 40‐story steel building was designed and used as an analysis model in this study, on the basis of the damping ratio from a structural performance test, using normal steel braces, BRB and H‐BRB. In addition, to evaluate the optimal location of H‐BRB, a time‐history analysis of four models was conducted in the study. For such time‐history analysis, wind‐load data in a 10‐year recurrence interval, which were calculated from the wind tunnel test, were used. The result of the time‐history analysis showed that H‐BRB is effective in improving both the lateral stiffness and serviceability of a building using the existing BRB. It also confirmed that it is most effective to position H‐BRBs mainly on the lower stories. Copyright © 2012 John Wiley & Sons, Ltd.     

地震作用下某高层结构MTMD减震控制研究

通过数值模拟研究了地震作用下高层结构多个调谐质量阻尼器(MTMD)减震控制。根据实际工程,利用国际通用软件ETABS建立了结构三维有限元模型,进行了动力特性的分析,得到了结构的前几阶频率;根据不同场地类型,选取了4条典型的地震波;研究了调谐质量阻尼器(TMD)的参数选取和有限元的模拟;运用时程分析方法,分别研究了不同地震作用下高层结构有无控制下的反应。研究结果表明,MTMD对高层结构的减震控制效果明显,场地类型对减震控制效果有一定的影响。所获得的结果为高层结构减震控制设计提供参考和依据。     

Semi‐active control devices in structural control implementation

A semi‐active control device for structural control implementations is presented and discussed in this paper. Based on two passive control devices, the mass pump and the hydraulic mass system, a new passive control system, the mass damper pump (MDP), is introduced. It is found that the MDP system is more effective in vibration control than the other two passive control systems. It is then shown that the passive control MDP can be modified to be a semi‐active control device and is very effective in structural control. Through theoretical analysis and numerical simulations, it is found that the proposed semi‐active control device MDP is more suitable for structures with ordinary height or the magnitude of earthquake excitations is not very large (because the control force provided by the semi‐active control is limited). Under these situations, the maximum response of a controlled structure can be reduced by one‐third to one‐half. Also, it is found that multiple MDP is more effective in reducing structural response than a single MDP when they are placed in appropriate locations. Copyright © 2005 John Wiley & Sons, Ltd.     

Semi-active fuzzy control of Lali Cable-Stayed Bridge using MR dampers under seismic excitation

Seismic control of cable-stayed bridges is of paramount importance due to their complex dynamic behavior, high flexibility, and low structural damping. In the present study, several semi-active Fuzzy Control Algorithms (FCAs) for vibration mitigation of Lali Cable-Stayed Bridge are devised. To demonstrate the efficiency of the algorithms, a comprehensive nonlinear 3-D model of the bridge is created using OpenSees. An efficient method for connecting MATLAB and OpenSees is devised for applying FCAs to the structural model of the bridge. Two innovative fuzzy rule-bases are introduced. A total of six different fuzzy rule-bases are utilized. The efficiency of the FCAs is evaluated in a comparative manner. The performance of fuzzy control systems is also compared with a sky-hook and a passive-on system. Moreover, the sensitivity of efficiency of control systems to the peak ground acceleration is evaluated qualitatively. In addition, the effect of time lag is also investigated. This study thoroughly examines the efficiency of the FCAs in different aspects. Therefore, the results can be regarded as a general guide to design semi-active fuzzy control systems for vibration mitigation of cable-stayed bridges.     

Coupled shear‐flexural model for dynamic analysis of fixed‐base tall buildings with tuned mass dampers

An equivalent discrete model is developed for time domain dynamic analysis of uniform high‐rise shear wall‐frame buildings with fixed base and carrying any number of tuned mass dampers (TMDs). The equivalent model consists of a flexural cantilever beam and a shear cantilever beam connected in parallel by a finite number of axially rigid members that allow the consideration of intermediate modes of lateral deformation. The proposed model was validated by a building whose lateral resisting system consists of a combination of shear walls and braced frames. The results showed the effectiveness of TMDs to reduce the peak displacements, interstory drift ratio, and accelerations when the building is subjected to a seismic load. The root mean square accelerations due to along‐wind loads also decrease if TMDs are attached to the building.     

Incremental dynamic collapse analysis of RC core‐wall tall buildings considering spatial seismic response distributions

Despite wide‐ranging studies on fragility analysis and collapse safety assessment of short to medium‐rise reinforced concrete (RC) structures, a new interest in the topic is still valuable and even necessary for tall RC buildings. This study aims at establishing fragility relationships as well as collapse probability of high‐rise RC core‐wall buildings under maximum considered earthquake ground motions. This study is carried out in a probabilistic framework on a case study of a fully 3‐dimensional numerical model developed to simulate seismic behavior of a 42‐story building having a RC core‐wall system. Proposing planar and vertical distributions of ductility and damage indices, the incremental dynamic analysis, and the multi‐direction nonlinear static (pushover) analyses were employed to reach the research goal. Median collapse‐level capacities were defined in terms of seismic responses (e.g., ductility/damage indices) as well as several intensity measures by employing statistical analyses and cumulative density functions. Available and acceptable collapse margin ratios were next estimated to quantify collapse safety at maximum considered earthquake shaking level. On an average basis, the statistics indicated 9%–10% and 5%–6% collapse probability of the building subjected to near‐ and far‐field ground motions, respectively.     

The wind‐induced response characteristics of atypical tall buildings

A tall building reacts sensitively to winds because the wind force increases according to the height and shape of the building. Various shapes of tall buildings and their aerodynamic characteristics have been studied extensively. For structural design and occupant comfort, the dynamic displacement of a tall building must be maintained within the criteria for acceptable levels of wind‐induced motion. An aerodynamically appropriate building shape needs to be selected at the design stage of a tall building. In this study, wind‐induced vibration responses were investigated, according to the criteria for maximum acceptable displacement and acceleration. Copyright © 2007 John Wiley & Sons, Ltd.