不规则高层结构基于新型电磁惯性质量阻尼器的半主动控制

为了研究新型电磁惯性质量阻尼器(Electromagnetic Inertial Mass Damper,EIMD)应用于偏心高层结构振动控制工程的可行性,鉴于半主动控制技术的优点,基于LQR主动控制算法,提出一种可行的EIMD-偏心高层结构半主动控制策略,同时研究EIMD在结构每层中安装位置不同对于控制偏心高层结构扭...     

Multi‐objective optimal design of FLC driven hybrid mass damper for seismically excited structures

Structural vibration control using active or passive control strategy is a viable technology for enhancing structural functionality and safety against natural hazards such as strong earthquakes and high wind gusts. Both the active and passive control systems have their limitations. The passive control system has limited capability to control the structural response whereas the active control system depends on external power. The power requirement for active control of civil engineering structures is usually quite high. Thus, a hybrid control system is a viable solution to alleviate some of the limitations. In this paper a multi‐objective optimal design of a hybrid control system for seismically excited building structures has been proposed. A tuned mass damper (TMD) and an active mass driver (AMD) have been used as the passive and active control components of the hybrid control system, respectively. A fuzzy logic controller (FLC) has been used to drive the AMD as the FLC has inherent robustness and ability to handle the non‐linearities and uncertainties. The genetic algorithm has been used for the optimization of the control system. Peak acceleration and displacement responses non‐dimensionalized with respect to the uncontrolled peak acceleration and displacement responses, respectively, have been used as the two objectives of the multi‐objective optimization problem. The proposed design approach for an optimum hybrid mass damper (HMD) system, driven by FLC has been demonstrated with the help of a numerical example. It is shown that the optimum values of the design parameters of the hybrid control system can be determined without specifying the modes to be controlled. The proposed FLC driven HMD has been found to be very effective for vibration control of seismically excited buildings in comparison with the available results for the same example structure but with a different optimal absorber. Copyright © 2002 John Wiley & Sons, Ltd.     

Adaptive bang–bang control for the vibration control of structures under earthquakes

An adaptive method based on the modified bang–bang control algorithm is proposed for the vibration control of structures subjected to unexpected severe seismic loads greater than the design loads. A hydraulic‐type active mass damper was made and experiments were carried out in the laboratory using a one‐story test structure and a five‐story test structure with the active mass damper. Through numerical simulations and experiments it was confirmed that the proposed method works well to suppress the vibration of structures subjected to unexpected severe seismic loads greater than the design loads without causing any unstable situations. Copyright © 2003 John Wiley & Sons, Ltd.     

Seismic response of intake towers including dam–tower interaction

The seismic response of the intake–outlet towers has been widely analyzed in recent years. The usual models consider the hydrodynamic effects produced by the surrounding water and the interior water, characterizing the dynamic response of the tower–water–foundation–soil system. As a result of these works, simplified added mass models have been developed. However, in all previous models, the surrounding water is assumed to be of uniform depth and to have infinite extension. Consequently, the considered added mass is associated with only the pressures created by the displacements of the tower itself. For a real system, the intake tower is usually located in proximity to the dam and the dam pressures may influence the equivalent added mass. The objective of this paper is to investigate how the response of the tower is affected by the presence of the dam. A coupled three‐dimensional boundary element‐finite element model in the frequency domain is employed to analyze the tower–dam–reservoir interaction problem. In all cases, the system response is assumed to be linear, and the effect of the internal fluid and the soil–structure interaction effects are not considered. The results suggest that unexpected resonance amplifications can occur due to changes in the added mass for the tower as a result of the tower–dam–reservoir interaction. Copyright © 2008 John Wiley & Sons, Ltd.     

Wavelet‐based non‐stationary seismic rocking response of flexibly supported tanks

The non‐stationary rocking response of liquid storage tanks under seismic base excitations including soil interaction has been developed based on the wavelet domain random vibration theory. The ground motion has been characterized through statistical functionals of wavelet coefficients of the ground acceleration history. The tank–liquid–foundation system is modelled as a multi‐degree‐of‐freedom (MDOF) system with both lateral and rocking motions of vibration of the foundation. The impulsive and convective modes of vibration of the liquid in the tank have been considered. The wavelet domain coupled dynamic equations are formulated and then solved to get the expressions of instantaneous power spectral density function (PSDF) in terms of functionals of input wavelet coefficients. The moments of the instantaneous PSDF are used to obtain the stochastic responses of the tank in the form of coefficients of hydrodynamic pressure, base shear and overturning base moment for the largest expected peak responses. Parametric variations are carried out to study the effects of various governing parameters like height of liquid in the tank, height–radius ratio of the tank, ratio of total liquid mass to mass of foundation, and shear wave velocity in the soil medium, on the responses of the tank. Copyright © 2003 John Wiley & Sons, Ltd.     

基于有限元分析高压输电塔结构的地震反应

输电塔结构是重要的生命线工程,对风和地震等环境荷载十分敏感。近几年,世界各地发生过多起输电塔破坏事件,给人们的生命财产和社会经济带来了巨大的损失。因此,对输电塔在风荷载和地震作用下进行更精确的分析就显得十分重要。本文采用SAP2000有限元分析软件,使用三维模型对高压输电塔结构进行多个地震动作用下的模拟计算分析。通过对同一输电塔结构输入多种不同的地震动,研究了地震的随机性对输电塔结构地震反应的影响。经对输电塔在不同地震动作用下地震结构反应的数据处理,比较其最大应力、最小应力和变形值,获得结构的地震反应特征。进一步将数据进行拟合得数值模拟计算的离散情况,从而给出不同地震动下输电塔结构地震反应的更一般情况。     

Soil–pile–structure interaction under SH wave excitation

A continuum model for the interaction analysis of a fully coupled soil–pile–structure system under seismic excitation is presented in this paper. Only horizontal shaking induced by harmonic SH waves is considered so that the soil–pile–structure system is under anti‐plane deformation. The soil mass, pile and superstructure were all considered as elastic with hysteretic damping, while geometrically both pile and structures were simplified as a beam model. Buildings of various heights in Hong Kong designed to resist wind load were analysed using the present model. It was discovered that the acceleration of the piled‐structures at ground level can, in general, be larger than that of a free‐field shaking of the soil site, depending on the excitation frequency. For typical piled‐structures in Hong Kong, the amplification factor of shaking at the ground level does not show simple trends with the number of storeys of the superstructure, the thickness and the stiffness of soil, and the stiffness of the superstructure if number of storeys is fixed. The effect of pile stiffness on the amplification factor of shaking is, however, insignificant. Thus, simply increasing the pile size or the superstructure stiffness does not necessarily improve the seismic resistance of the soil–pile–structure system; on the contrary, it may lead to excessive amplification of shaking for the whole system. Copyright © 2003 John Wiley & Sons, Ltd.     

矩形高层建筑扭转动力风荷载解析模型

本文通过研究不同长宽比、高宽比的矩形棱柱体在边界层风洞中典型攻角下的扭矩，提出了矩形高层建筑扭矩功率谱密度、均方根扭矩系数和Strouhal数的经验公式，并对相干函数作了一定的探讨，建立了完整的扭转动力风荷载解析模型。该模型和试验结果吻合较好，证明它是合理有效的，可在此基础上建立高层建筑扭转动力响应频域计算方法。     

Estimation of relative displacement of two adjacent asymmetric structures

The most straightforward method to mitigate seismic pounding damage to adjacent structures is to provide adequate separation distance between them to completely preclude pounding during strong shaking. Many studies on the necessary separation distance between adjacent structures have been reported recently. Seismic codes around the world also specify the minimum required separation distances. However, all those required separations were derived by considering only the lateral responses of structures. For asymmetric structures with coupled torsional–lateral responses, the required separations are not well investigated. This paper presents some parametric study results on the relative displacement of adjacent asymmetric structures by considering their coupled torsional–lateral responses. Random vibration method is employed in the analysis. Both elastic and inelastic responses are considered. Effects of vibration frequencies, torsional stiffness and eccentricities of adjacent structures on their relative displacements are investigated. Numerical results are presented in dimensionless form and are discussed with respect to the current code specifications. Copyright © 2001 John Wiley & Sons, Ltd.     

Failure simulation of shear‐critical RC columns with non‐ductile detailing under lateral load

Reinforced concrete columns with non‐ductile detailing typically exhibit a softening behavior characterized by severe degradation when subjected to cyclic lateral loads. Whether the response is brittle or ductile, shear failure occurs with an inclined through crack along which sliding occurs coupled with loss of horizontal and vertical load‐bearing capacity of the member. The rapid loss of resistance after the peak strength is reached is because of one or more of the following local failure mechanisms: brittle failure of poorly confined concrete; buckling of longitudinal reinforcing bars because of lack of adequate transverse reinforcement or following opening of stirrups after spalling of cover concrete; bond failure. In this study, a modeling strategy to build a detailed 3D finite element model capable of capturing all of the above‐mentioned local failure mechanisms is presented. In particular, a steel–concrete interface model for representing the interaction within the member between concrete core, cover and longitudinal and transverse reinforcement is proposed. Comparison with results of an experimental test of a shear‐sensitive column demonstrates the effectiveness of the simulation up to failure of the element. Copyright © 2016 John Wiley & Sons, Ltd.     

Multiobjective optimal FLC driven hybrid mass damper system for torsionally coupled,seismically excited structures

In most of the research work on structural vibration control only two‐dimensional plane structural modelling has been considered, although only a few practical building structures can be modelled as planar structures. Therefore, these methods are not directly applicable to the majority of the practical building structures. This paper discusses the design of a multiobjective optimal fuzzy logic controller (FLC) driven hybrid mass damper (HMD) system for seismically excited torsionally coupled building structures. Floor acceleration and velocity information have been used as feedback to the fuzzy logic controller. A three branch tournament Genetic Algorithm has been used for the multiobjective optimal design of the FLC driven HMD system, where the minimization of the non‐dimensionalized peak displacement, acceleration and rotation of the structure about its vertical axis, have been as the three objective functions. The proposed multiobjective optimal fuzzy logic controller has been verified for an example problem reported in the literature. This HMD system consists of four HMDs arranged in such a way that the system can control the torsional mode of vibration effectively in addition to the flexure modes of vibration. Copyright © 2002 John Wiley & Sons, Ltd.     

Seismic vulnerability of offshore wind turbines to pulse and non-pulse records

The increasing number of wind turbines in active tectonic regions has attracted scientific interest to evaluate the seismic vulnerability of offshore wind turbines (OWTs). This study aims at assessing the deformation and collapse susceptibility of 2MW and 5MW OWTs subjected to shallow-crustal pulse-like ground motions, which has not been particularly addressed to date. A cloud-based fragility assessment is performed to quantify the seismic response for a given intensity measure and to assess the failure probabilities for pulse-like and non-pulse-like ground motions. The first-mode spectral acceleration S_a(T₁) is found to be an efficient response predictor for OWTs, exhibiting prominent higher-mode behavior, at the serviceability and ultimate conditions. Regardless of earthquake type, it is shown that records with strong vertical components may induce nonlinearity in the supporting tower, leading to potential failure by buckling in three different patterns: (i) at tower base near platform level, (ii) close to tower top, and (iii) between the upper half of the main tower and its top. Type and extent of the damage are related to the coupled excitation of vertical and lateral higher modes, for which tower top acceleration response spectra S_a,i(Top) is an effective identifier. It is also observed that tower's slenderness ratio (l/d), the diameter-to-thickness ratio (d/t), and the rotor-nacelle-assembly mass (m_RNA) are precursors for evaluating the damage mode and vulnerability of OWTs under both pulse-like and non-pulse-like ground motion records.     

Dynamic interaction of bridge–train system under non‐uniform seismic ground motion

The probability that an earthquake occurs when a train is running over a bridge in earthquake‐prone regions is much higher than before, for high‐speed railway lines are rapidly developed to connect major cities worldwide. This paper presents a finite element method‐based framework for dynamic analysis of coupled bridge–train systems under non‐uniform seismic ground motion, in which rail–wheel interactions and possible separations between wheels and rails are taken into consideration. The governing equations of motion of the coupled bridge–train system are established in an absolute coordinate system. Without considering the decomposition of seismic responses into pseudo‐static and inertia‐dynamic components, the equations of motion of the coupled system are formed in terms of displacement seismic ground motions. The mode superposition method is applied to the bridge structure to make the problem manageable while the Newmark‐β method with an iterative computation scheme is used to find the best solution for the problem concerned. Eight high‐speed trains running over a multi‐span steel truss‐arch bridge subject to earthquakes are taken as a case study. The results from the case study demonstrate that the spatial variation of seismic ground motion affects dynamic responses of the bridge–train system. The ignorance of pseudo‐static component when using acceleration seismic ground motions as input may underestimate seismic responses of the bridge–train system. The probability of separation between wheels and rails becomes higher with increasing train speed. Copyright © 2011 John Wiley & Sons, Ltd.     

Semi‐active neuro‐control for base‐isolation system using magnetorheological (MR) dampers

Vibration mitigation using smart, reliable and cost‐effective mechanisms that requires small activation power is the primary objective of this paper. A semi‐active controller‐based neural network for base‐isolation structure equipped with a magnetorheological (MR) damper is presented and evaluated. An inverse neural network model (INV‐MR) is constructed to replicate the inverse dynamics of the MR damper. Next, linear quadratic Gaussian (LQG) controller is designed to produce the optimal control force. Thereafter, the LQG controller and the INV‐MR models are linked to control the structure. The coupled LQG and INV‐MR system was used to train a semi‐active neuro‐controller, designated as SA‐NC, which produces the necessary control voltage that actuates the MR damper. To evaluate the proposed method, the SA‐NC is compared to passive lead–rubber bearing isolation systems (LRBs). Results revealed that the SA‐NC was quite effective in seismic response reduction for wide range of motions from moderate to severe seismic events compared to the passive systems. In addition, the semi‐active MR damper enjoys many desirable features, such as its inherent stability, practicality and small power requirements. The effectiveness of the SA‐NC is illustrated and verified using simulated response of a six‐degree‐of‐freedom model of a base‐isolated building excited by several historical earthquake records. Copyright © 2006 John Wiley & Sons, Ltd.     

近断层地震动作用下风机塔地震反应分析

为了研究近断层地震动速度脉冲及强竖向地震动对风机塔地震响应的影响,以某陆上风电场1.5 MW风机塔为研究对象开展了结构在水平向脉冲型地震动、水平向非脉冲型地震动、水平与竖向地震动组合3种地震输入工况的时程分析。通过3种工况下塔顶位移时程、加速度时程、塔底剪力、弯矩及轴力的对比分析发现:近断层速度脉冲对结构塔顶水平位移、塔顶水平加速度、塔底剪力与弯矩均影响显著;竖向地震动会加大结构的塔顶竖向加速度响应及塔底轴力响应;随着竖向与水平加速度峰值比增大,塔顶竖向加速度响应增大,最大轴力随着峰值比增大而增大,最小轴力随着峰值比增大而减小。此外,增量动力分析表明,采用自接触的有限元模型可以更真实地预测风机塔的失稳破坏机制。     

Systematic assessment of irregular building–soil interaction using efficient modal analysis

In this paper an efficient methodology applying modal analysis is developed to assess systematically the combined soil–structure interaction and torsional coupling effects on asymmetric buildings. This method is implemented in the frequency domain to accurately incorporate the frequency‐dependent foundation impedance functions. For extensively extracting the soil–structure interaction effects, a diagonal transfer matrix in the modal space is derived. A comprehensive investigation of asymmetric building–soil interaction can then be conveniently conducted by examining various types of response quantities. Results of parametric study show that the increasing height‐to‐base ratio of a structure generally amplifies its translational and torsional responses. Moreover, both the translational and torsional responses are reduced for the case where the two resonant frequencies are well separated and this reduction is enhanced with the decreasing values of the relative soil stiffness and the height‐to‐base ratio. The most noteworthy phenomenon may be the fact that the SSI effects can enlarge the translational response if the structure is slender and the two resonant frequencies are very close. Copyright © 2001 John Wiley & Sons, Ltd.     

压电材料智能摩擦阻尼器对高耸钢塔结构风振反应的半主动控制

压电材料是一种新型智能材料。本文将压电材料和被动摩擦阻尼器相结合设计出一种新型智能摩擦阻尼器,并采用基于经典最优控制理论的半主动控制策略对高耸钢塔结构风振反应的控制进行了研究,对国内即将兴建的第一高钢电视塔──合肥翡翠电视塔进行了算例分析。为满足摩擦阻尼器对高耸钢塔结构风振控制的特殊需要、文中还建立了房耸钢塔结构的空间桁架有限元模型和串联多自由度体系模型,并在形成广义控制力作用位置矩阵和计算摩擦阻尼器两端的相对位移的过程中综合地运用了这两种力学模型。本文研究表明,压电材料智能摩擦阻尼器可以有效地抑制高耸钢塔结构的风振反应。     

Dynamic analysis of offshore wind turbine in clay considering soil–monopile–tower interaction

A comprehensive study is performed on the dynamic behavior of offshore wind turbine (OWT) structure supported on monopile foundation in clay. The system is modeled using a beam on nonlinear Winkler foundation model. Soil resistance is modeled using American Petroleum Institute based cyclic p–y and t–z curves. Dynamic analysis is carried out in time domain using finite element method considering wind and wave loads. Several parameters, such as soil–monopile–tower interaction, rotor and wave frequencies, wind and wave loading parameters, and length, diameter and thickness of monopile affecting the dynamic characteristics of OWT system and the responses are investigated. The study shows soil–monopile–tower interaction increases response of tower and monopile. Soil nonlinearity increases the system response at higher wind speed. Rotor frequency is found to have dominant role than blade passing frequency and wave frequency. Magnitude of wave load is important for design rather than resonance from wave frequency.     

Modeling of an actively braced full‐scale building considering control–structure interaction

Recently, the application of active control to seismic‐excited buildings has attracted international attention. To demonstrate the practical applicability of active control, we have conducted experimental tests using a full‐scale three‐storey building equipped with active bracing systems on the shake table at the National Center for Research on Earthquake Engineering (NCREE), Taiwan. Experimental results indicate that the control–structure interaction (CSI) effect is significant. A state‐space analytical model of this actively controlled building taking into account the CSI effect is established in this paper using a system identification technique based on curve‐fitting of transfer functions. To verify the accuracy of the analytical model for simulating the controlled response, four sets of linear quadratic Gaussian (LQG) controllers using acceleration feedback are designed and further experimental tests are conducted for comparison. It is demonstrated that the correlations between the simulation and experimental results are remarkable. The construction of an accurate analytical model is important for active control, and such an analytical model can be used for future benchmark studies of different control algorithms based on numerical simulations. Copyright © 2000 John Wiley & Sons, Ltd.     

Vertical earthquake response of megawatt‐sized wind turbine with soil‐structure interaction effects

The dynamic response of a wind turbine on monopile is studied under horizontal and vertical earthquake excitations. The analyses are carried out using the finite element program SAP2000. The finite element model of the structure is verified against the results of shake table tests, and the earthquake response of the soil model is verified against analytical solutions of the steady‐state response of homogeneous strata. The focus of the analyses in this paper is the vertical earthquake response of wind turbines including the soil‐structure interaction effects. The analyses are carried out for both a non‐homogeneous stratum and a deep soil using the three‐step method. In addition, a procedure is implemented which allows one to perform coupled soil‐structure interaction analyses by properly tuning the damping in the tower structure. The analyses show amplification of the ground surface acceleration to the top of the tower by a factor of two. These accelerations are capable of causing damage in the turbine and the tower structure, or malfunctioning of the turbine after the earthquake; therefore, vertical earthquake excitation is considered a potential critical loading in design of wind turbines even in low‐to‐moderate seismic areas. Copyright © 2015 John Wiley & Sons, Ltd.