双向偏心结构扭转耦联地震反应的序列最优控制

本文分析了不对称建筑结构平移-扭转耦联振动的动力特性及地震作用下的响应;根据地震动输入结构的过程,推导出一种更为一般的最优控制算法,所获得的控制力表达式同时包括地震响应和地震激励。通过对一非规则四层框架结构的扭转耦联地震反应控制分析表明,该算法不仅能有效地控制结构的平移地震反应,而且更有效地抑制结构的扭转耦联地震反应。     

结构地震反应的瞬时KCE控制

提出了地震作用下结构主动控制的瞬时ＫＣＥ控制，给出参数的优化确定方法，并针对某试验用模型结构进行了计算和分析。结果表明，瞬时ＫＣＥ控制算法明显优于瞬时最优控制算法。     

结构偏心对基础隔震结构地震反应的影响

本文对基础隔震偏心结构在不同场地上的地震动作用下的反应进行了深入研究，探讨了上部结构偏心、隔震层偏心、场地条件等因素对于基础隔震结构地震反应的影响，选取了能反映结构偏心特性的参数，以便将分析各因素对隔震结构地震反应的影响转化为分析参数的影响。通过大量的数值计算与分析，得到了一些对实际工程有意义的结论。     

复合隔震结构地震反应的简化计算

对单质点复合隔震结构的振动进行了分析，并导出了通过迭代计算复合隔城结构最大地震反应的简化公式，该计算公式可用于砌体隔震结构及类似结构初步设计的估算。     

隔震结构地震反应分析的实用计算方法

根据上部结构和隔震单元特性对隔震结构反应的影响,提出了可用于隔震结构反应分析的简易方法,避免从数学上求解耦联的非线性方程.将隔震层的恢复力模型等效线性化,以结构动力响应的Duhamel积分为基础,提出了一种新的结构动力响应的数值计算方法.     

基于强震观测的隔震结构地震反应分析

福建省防灾减灾中心大楼是一栋高约40m,安装有强震观测系统的隔震大楼,目前该结构台阵已记录到30多次地震引起的大楼地震反应。本文利用具有强大非线性功能的ETABS软件建立大楼结构模型,同时考虑隔震结构的楼梯和填充墙对结构地震反应的影响,并利用台阵记录验证大楼结构模型线弹性地震反应的可靠性,说明隔震大楼结构模型能很好地模拟大楼的地震反应过程。在此基础上结合大楼原型动力性能实验的实测参数,以大楼自由场地的三个实际地震记录作为输人,对大楼在中小地震作用下非线性地震反应进行分析,结果表明大楼具有良好的隔震效果。     

基础隔震单层偏心结构扭转地震反应分析

采用微分型滞回恢复力模型模拟隔震支座的恢复力特性，对基础隔震单层偏心结构的扭转地震反应进行分析，研究隔震系统偏心距和上部结构偏心距对结构扭转反应的影响。结果表明，采用隔震技术可以显著降低隔震结构的扭转地震反应。     

摩擦隔震结构中不同摩擦力模型在地震作用下结构响应分析

本文选用两种摩擦力模型来分析隔震结构的地震响应，运用newmark方法推导了隔震结构采用库仑摩擦力模型在地震作用下结构响应的计算公式。并编程计算了实例，进行了综合分析，得出质量比、摩擦系数对隔震效果的影响；并给出在其他结构参数相对稳定的条件下，滑移面摩擦系数的取值范围。     

基于序列最优控制算法的隔震曲线梁桥非线性振动控制研究

强震作用下隔震曲线梁桥会产生较大的弹塑性变形,需要采取一定的控制措施以保证其安全性。采用经典的Bouc-Wen模型,建立考虑上部结构偏心的隔震曲线梁桥的非线性动力方程,求解罕遇地震作用下结构的动力响应。针对隔震曲线梁桥罕遇地震作用下产生的较大弹塑性变形,建立隔震曲线梁桥的非线性振动控制方程,将该方程等效线性化后采用序列最优控制算法(SOC)和经典线性最优控制(COC)对桥梁进行振动控制研究。结果表明：在罕遇地震下,隔震曲线梁桥的下部结构与隔震层都已屈服进入塑性阶段,且有少量的残余位移产生;序列最优控制算法和经典线性最优控制都能有效地减小隔震曲线梁桥弹塑性状态下的平动位移与残余位移,并有效抑制曲线桥的扭转效应,其中序列最优控制算法较经典最优控制更能显著削减隔震曲线梁桥的峰值响应。     

复杂地震激励下隔震结构地震响应研究进展

隔震技术作为当前最有效的结构减震控制技术之一,在世界各国高烈度地区广泛建造。随着隔震技术的大范围推广,建造工况更为复杂的隔震工程随之不断涌现。系统深入研究复杂地震激励下隔震结构地震响应,是隔震工程长期安全服役的重要保障,也是隔震技术能够不断完善和推广的坚实基础。本文从复杂地震激励涵盖的多维地震、近场和近断层地震、行波效应以及土与结构相互作用四个主要方面入手,依据国内外相关文献开展综述,探讨了复杂地震激励下隔震结构研究存在的问题,并对此进行展望。     

大震下被动与智能隔震结构动力可靠度的对比

对被动及智能隔震结构在“大震”条件下的动力可靠度进行探讨。将被动及智能隔震体系均取作弹塑性模型,并用退化Bouc-W en滞变模型描述上部结构的恢复力,用非退化Bouc-W en模型描述隔震层的恢复力。采用虚拟激励法计算结构的随机响应,根据我国抗震规范中“大震不倒”的设防目标,采用各层最大层间位移峰值响应和累积滞变耗能构造双参数的随机疲劳累积损伤指数,作为功能状态指标。假定各层失效相关,用串联系统计算体系动力可靠度。通过数值算例,对比了被动隔震、智能隔震与非隔震体系的条件失效概率,从动力可靠度角度显示了智能隔震体系的减震优势。     

Predictive optimal control for seismic analysis of non-linear and hysteretic structures

In this paper, an effective active predictive control algorithm is developed for the vibration control of non-linear hysteretic structural systems subjected to earthquake excitation. The non-linear characteristics of the structural behaviour and the effects of time delay in both the measurements and control action are included throughout the entire analysis (design and validation). This is very important since, in current design practice, structures are assumed to behave non-linearly, and time delays induced by sensors and actuator devices are not avoidable. The proposed algorithm focuses on the instantaneous optimal control approach for the development of a control methodology where the non-linearities are brought into the analysis through a non-linear state vector and a non-linear open-loop term. An autoregressive (AR) model is used to predict the earthquake excitation to be considered in the prediction of the structural response. A performance index that is quadratic in the control force and in the predicted non-linear states, with two additional energy related terms, and that is subjected to a non-linear constraint equation, is minimized at every time step. The effectiveness of the proposed closed-open loop non-linear instantaneous optimal prediction control (CONIOPC) strategy is presented by the results of numerical simulations. Since non-linearity and time-delay effects are incorporated in the mathematical model throughout the derivation of the control methodology, good performance and stability of the controlled structural system are guaranteed. Copyright © 1999 John Wiley & Sons, Ltd.     

Predictive instantaneous optimal control of elastic structures during earthquakes

A predictive instantaneous optimal control (PIOC) algorithm is proposed for controlling the seismic responses of elastic structures. This algorithm compensates for the time delay that happens in practical control applications by predicting the structural response over a period that equals the time delay, and by substituting the predicted response in the instantaneous optimal control (IOC) algorithm. The unique feature of this proposed PIOC algorithm is that it is simple and at the same time compensates for the time delay very effectively. Numerical examples of single degree of freedom structures are presented to compare the performance of PIOC and IOC systems for various time delay magnitudes. Results show that a time delay always causes degradation of control efficiency, but PIOC can greatly reduce this degradation compared to IOC. The effects of the structure's natural periods and the choice of control gains on the degradation induced by the time delay are also analyzed. Results show that shorter natural periods and larger control gains are both more sensitive and more serious to the degradation of control efficiency. Finally, a practical application of PIOC is performed on a six‐story moment‐resisting steel frame. It is demonstrated that PIOC contributes significantly to maintain stability in multiple degree of freedom structures, and at the same time PIOC has a satisfactory control performance. Copyright © 2003 John Wiley & Sons, Ltd.     

对称结构在水平地震作用下的扭转效应和抗扭设计探讨

针对水平地震作用下对称结构抗扭设计中存在的问题,分析了对称结构扭转振动的原因,然后分别采用静力和动力方法研究了考虑偶然偏心作用时结构反应的增大效应,比较了这两种方法计算结果的异同,最后结合我国抗震规范提出了适当的结论和改进建议,为对称结构的抗扭设计提供了理论依据。     

高层钢结构地震反应形状记忆合金拉索控制研究

本文通过形状记忆合金(SMA)材料的超弹性性能试验确定了SMA材料的各项参数和常温状态下的本构模型。对采用SMA拉索实施振动控制的20层钢结构的Benchmark模型的地震响应进行了时程分析。计算结果表明,实施SMA拉索控制后,层间相对位移可降低70％左右,且SMA材料很好的耗能作用有效地减少了地震能量向上部楼层的传递,对上部结构具有一定的隔振作用;顶层相对位移的控制效果达到51％;顶层加速度可降低43％;地震波强度和拉索初应变对拉索的被动控制效果影响较大。最后给出了拉索的安装位置与拉索的应变之间的关系曲线,建议了合理的布置方案。     

Sampled-data H2 optimal output feedback control for civil structures

An optimal control method involving sampled data is considered for use in earthquake and wind engineering applications. The structure is modelled as a continuous system attached to a discrete-time controller using zero-order sample-and-hold devices. Examples of two buildings with active base isolators and a 163 m tall planar frame with an active mass damper are considered. The buildings with the base isolators are subjected to excitation input using the 1940 El Centro earthquake (NS component) as an example, while the planar frame is subjected to assumed sinusoidal gusts with a period close to that of the frame. The controlled responses (with and without time delays) are studied. To further analyze the features of the control designs, the building examples with base isolators are subjected to five other different earthquake excitation records. Trends in control performance and effectiveness are presented and discussed. The results suggest that such systems are potentially suited for implementation in the vibration control of civil infrastructures; such potentiality becomes more realistic with the current trends in software development and the increased use of digital computers. Copyright © 1999 John Wiley & Sons, Ltd.     

Experimental study of identification and control of structures using neural network. Part 2: control

Experimental verifications of a recently developed active structural control method using neural networks are presented in this paper. The experiments were performed on the earthquake simulator at the University of Illinois at Urbana—Champaign. The test specimen was a 1/4 scale model of a three-storey building. The control system consisted of a tendon/pulley system controlled by a single hydraulic actuator at the base. The control mechanism was implemented through four active pre-tensioned tendons connected to the hydraulic actuator at the first floor. The structure modelling and system identification has been presented in a companion paper. (Earthquake Engng. Struct. Dyn. 28 , 995–1018 (1999)). This paper presents the controller design and implementation. Three controllers were developed and designed: two neurocontrollers, one with a single sensor feedback and the other with three sensor feedback, and one optimal controller with acceleration feedback. The experimental design of the neurocontrollers is accomplished in three steps: system identification, multiple emulator neural networks training and finally the neurocontrollers training with the aid of multiple emulator neural networks. The effectiveness of both neurocontrollers are demonstrated from experimental results. The robustness and the relative stability are presented and discussed. The experimental results of the optimal controller performance is presented and assessed. Comparison between the optimal controller and neurocontrollers is presented and discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Tuned mass dampers for response control of torsional buildings

This paper presents an approach for optimum design of tuned mass dampers for response control of torsional building systems subjected to bi‐directional seismic inputs. Four dampers with fourteen distinct design parameters, installed in pairs along two orthogonal directions, are optimally designed. A genetic algorithm is used to search for the optimum parameter values for the four dampers. This approach is quite versatile as it can be used with different design criteria and definitions of seismic inputs. It usually provides a globally optimum solution. Several optimal design criteria, expressed in terms of performance functions that depend on the structural response, are used. Several sets of numerical results for a torsional system excited by random and response spectrum models of seismic inputs are presented to show the effectiveness of the optimum designs in reducing the system response. Copyright © 2002 John Wiley & Sons, Ltd.     

Seismic response control of frame structures using magnetorheological/electrorheological dampers

Semi‐active control of buildings and structures for earthquake hazard mitigation represents a relatively new research area. Two optimal displacement control strategies for semi‐active control of seismic response of frame structures using magnetorheological (MR) dampers or electrorheological (ER) dampers are proposed in this study. The efficacy of these displacement control strategies is compared with the optimal force control strategy. The stiffness of brace system supporting the smart damper is also taken into consideration. An extensive parameter study is carried out to find the optimal parameters of MR or ER fluids, by which the maximum reduction of seismic response may be achieved, and to assess the effects of earthquake intensity and brace stiffness on damper performance. The work on example buildings showed that the installation of the smart dampers with proper parameters and proper control strategy could significantly reduce seismic responses of structures, and the performance of the smart damper is better than that of the common brace or the passive devices. The optimal parameters of the damper and the proper control strategy could be identified through a parameter study. Copyright © 2000 John Wiley & Sons, Ltd.     

The role of strong motion rotations in the response of structures near earthquake faults

Early studies of earthquake strong motion assumed linear materials and small deformations. It was observed that under favorable conditions (long waves), the accompanying rotational motions are usually small, and so their effects could be neglected. In 1932, when Biot opted for the vibrational method of solution of the dynamic response problems [Trifunac MD. 75th anniversary of the response spectrum method—a historical review. Soil Dyn Earthquake Eng 2008 [in press].] in his formulation of the response spectrum concept, his choice of the discrete mathematical models of buildings further led to the conditions that did not explicitly require consideration of the rotations [Trifunac MD. Buildings as sources of rotational waves, Chapter I.5. In: Teisseyre R, Nagahama H, Majewski E, editors. Physics of asymmetric continua: extreme and fracture processes. Heidelberg, Germany: Springer; 2008 [in press].]. The engineering profession was not prepared in the 1930s and 1940s for Biot's new theory and first had to learn the basic dynamics of structures before it could question the wisdom and consequences of the vibrational versus the wave-propagation approaches to the solution. Also, there were too many other concerns, often caused by the modeling simplifications, that pushed the studies of the rotational motion further down to the low levels of priority. Even today, 40 years after the arrival of digital computers and the emergence of powerful numerical computational capabilities, which uncovered unexpectedly large families of chaotic solutions accompanying large deformations, as well as nonlinear response [Trifunac MD. Nonlinear problems in earthquake engineering. In: Springer's encyclopedia of complexity and system science, 2008 [in press] [94].], most researchers continue to ignore the role of rotations. Had Biot chosen the wave-propagation approach for the solution of the earthquake engineering problems in 1932, the “progress” might have been faster. The wave representation can be differentiated with respect to a space coordinate, giving the rotations at a point directly. In contrast, the lumped-mass models in the vibrational approach do not make this possible, and the closest one can come to considering rotations is in terms of average, per-floor rotation, or drift.