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1.
Shake tables provide a direct means by which to evaluate structural performance under earthquake excitation. Because the entire structure is mounted on the base plate and subjected to the ground motion in real time, dynamic effects and rate‐dependent behavior can be accurately represented. Shake table control is not straightforward as the desired signal is an acceleration record, while most actuators operate in displacement feedback for stability. At the same time, the payload is typically large relative to the capacity of the actuator, leading to pronounced control‐structure interaction. Through this interaction, the dynamics of the specimen influence the dynamics of the shake table, which can be problematic when specimens change behavior because of damage or other nonlinearities. Moreover, shake tables are themselves inherently nonlinear, making it difficult to accurately recreate a desired acceleration record over a broad range of amplitudes and frequencies. A model‐based multi‐metric shake table control strategy is proposed to improve tracking of the desired acceleration of a uniaxial shake table, remaining robust to nonlinearities including changes in specimen condition. The proposed strategy is verified for the shake table testing of both linear and nonlinear structures. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Development of high‐performance shake tables using the hierarchical control strategy and nonlinear control techniques 
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下载免费PDF全文 Conventional shake tables employ linear controllers such as proportional‐integral‐derivative or loop shaping to regulate the movement. However, it is difficult to tune a linear controller to achieve accurate and robust tracking of different reference signals under payloads. The challenges are mainly due to the nonlinearity in hydraulic actuator dynamics and specimen behavior. Moreover, tracking a high‐frequency reference signal using a linear controller tends to cause actuator saturation and instability. In this paper, a hierarchical control strategy is proposed to develop a high‐performance shake table. A unidirectional shake table is constructed at the University of British Columbia to implement and evaluate the proposed control framework, which consists of a high‐level controller and one or multiple low‐level controller(s). The high‐level controller utilizes the sliding mode control (SMC) technique to provide robustness to compensate for model nonlinearity and uncertainties experienced in experimental tests. The performance of the proposed controller is compared with a state‐of‐the‐art loop‐shaping displacement‐based controller. The experimental results show that the proposed hierarchical shake table control system with SMC can provide superior displacement, velocity and acceleration tracking performance and improved robustness against modeling uncertainty and nonlinearities. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Among several different experimental techniques, used to test the response of structures and to verify their seismic performance, the shake table testing allows to reproduce the conditions of true effects of earthquake ground motions in order to challenge complex model structures and systems. However, the reproduction of dynamic signals, due to the dynamics of the shake table and of the specimen, is usually imperfect even though closed‐loop control in a shake table system is used to reduce these errors and obtain the best fidelity reproduction. Furthermore, because of the dynamic amplifications in the specimen, the signal recorded at desired locations could be completely different from the expected effect of shake table motion. This paper focuses on the development of practical shake table simulations using additional ‘open loop’ feedforward compensation in form of inverse transfer functions (i.e. the ratio of the output structural response to an input base motion in the frequency domain) in order to obtain an acceptable reproduction of desired acceleration histories at specific locations in the specimen. As the first step, a well‐known global feedforward procedure is reformulated for the compensation of the table motion distortions due to the servo‐hydraulic system. Subsequently, the same concept is extended to the table‐structure system to adjust the shake table input in order to achieve a desired response spectrum at any floor of the specimen. Implementations show how such a method can be used in any experimental facility. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Narutoshi Nakata 《地震工程与结构动力学》2013,42(2):261-275
Effective force testing (EFT) is one of the force‐based experimental methods used for performance evaluation of structures that incorporate dynamic force control using hydraulic actuators. Although previous studies have shown successful implementations of force control, controllable frequency ranges are limited to low frequencies (10 Hz). This study presents the EFT method using a robust loop shaping force feedback controller that can extend the frequency range up to 25 Hz or even higher. Unlike the conventional PID controllers, loop shaping controllers can provide robustness for a high level of force measurement noise. This study investigates the dynamic properties of hydraulic actuators and the design of a loop shaping controller that compensates for control–structure interaction and suppresses the effect of oil‐column resonance. The designed loop shaping controller was successfully implemented into an EFT setup at the Johns Hopkins University. An experimental investigation of the loop shaping controller was performed under step, random, and earthquake force loadings. Experimental results showed that the loop shaping controller provided excellent force tracking performance and robustness for dynamic force loadings. It was also shown that the loop shaping controller had the gain margin of 9.54 dB at the frequency of 28 Hz. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The objective of this study was to investigate the effects of near-fault ground motions on substandard bridge columns and piers. To accomplish these goals, several large scale reinforced concrete models were constructed and tested on a shake table using near- and far-field ground motion records. Because the input earthquakes for the test models had different characteristics, three different measures were used to evaluate the effect of the input earthquake. These measures are peak shake table acceleration, spectral acceleration at the fundamental period of the test specimens, and the specimen drift ratios. For each measure, force-displacement relationships, strains, curvatures, drift ratios, and visual damage were evaluated. Results showed that regardless of the measure of input or response, the near-fault record generally led to larger strains, curvatures, and drift ratios. Furthermore, residual displacements were small compared to those for columns meeting current seismic code requirements. 相似文献
7.
Dynamic substructuring refers to physical testing with computational models in the loop. This paper presents a new strategy for such testing. The key feature of this strategy is that it decouples the substructuring controller from the physical subsystem. Unlike conventional approaches, it does not explicitly include a tracking controller. Consequently, the design and implementation of the substructuring controls are greatly simplified. This paper motivates the strategy and discusses the main concept along with details of the substructuring control design. The focus is on configurations that use shake tables and active mass drivers. An extensive experimental assessment of the new strategy is presented in a companion paper, where the influence of various factors such as virtual subsystem dynamics, control gains, and nonlinearities is investigated, and it is shown that robustly stable and accurate substructuring is achieved. 相似文献
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Shake table test of soil-pile groups-bridge structure interaction in liquefiable ground 总被引：2，自引：1，他引：1
<正>This paper describes a shake table test study on the seismic response of low-cap pile groups and a bridge structure in liquefiable ground.The soil profile,contained in a large-scale laminar shear box,consisted of a horizontally saturated sand layer overlaid with a silty clay layer,with the simulated low-cap pile groups embedded.The container was excited in three E1 Centra earthquake events of different levels.Test results indicate that excessive pore pressure(EPP) during slight shaking only slightly accumulated,and the accumulation mainly occurred during strong shaking.The EPP was gradually enhanced as the amplitude and duration of the input acceleration increased.The acceleration response of the sand was remarkably influenced by soil liquefaction.As soil liquefaction occurred,the peak sand displacement gradually lagged behind the input acceleration;meanwhile,the sand displacement exhibited an increasing effect on the bending moment of the pile,and acceleration responses of the pile and the sand layer gradually changed from decreasing to increasing in the vertical direction from the bottom to the top.A jump variation of the bending moment on the pile was observed near the soil interface in all three input earthquake events.It is thought that the shake table tests could provide the groundwork for further seismic performance studies of low-cap pile groups used in bridges located on liquefiable groun. 相似文献
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西南交通大学建成的8m×10m/160t振动台是目前国内规模最大的振动台,对其运行质量和振动影响进行评价具有示范效应。探讨该振动台振动影响的现场实验于2017年初展开,实测结果表明:该振动台在工作频段内受控性能很好,对地震动信号重现度很高;台面满载满负荷运行时实验室建筑基础10m以内地面振动加速度实测值不超过6.6gal,振动速度小于2mm/s,不会对实验室厂房及附属办公建筑的安全、使用舒适性及人们正常工作、生活造成不利影响。 相似文献
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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. 相似文献
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Base isolation is an effective way to reduce earthquake energy transfer from ground to structure, but existing seismic isolation systems are not very suitable for rural buildings for some reasons. A new steel–asphalt composite layer for the seismic base isolation of housing units is present in this paper. Its dynamic characteristics and isolation effect are studied by shake table tests of two full-scale specimens. Different earthquake waves with different peak ground accelerations (PGA, from 0.1 g to 0.4 g) are input. Test results show that the isolation layer could efficiently reduce the input acceleration. Moreover, as the PGA increase, the isolation layer shows good function of the displacement limit. 相似文献
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2008年汶川地震中江油市太白公园曲径桥上的石雕发生转动破坏现象,本文对这一转动现象进行了振动台模拟试验。模拟试验结果表明:① 在振动台三向加载1.5倍的汶川地震江油台记录的平动加速度后,模型的转动情况与实际观测的石雕转动情况比较一致;② 石雕的转动与石雕的非对称性、地震动输入角度和地震动的竖向作用有关;③ 加载竖向地震动作用后,石雕模型会发生摇摆现象,说明竖向地震动是造成模型扭转现象的重要原因,这也说明在分析相似震害现象时竖向地震动作用不可忽视。 相似文献
13.
Behavior of rigid blocks with geometrical defects under seismic motion: an experimental and numerical study 下载免费PDF全文
下载免费PDF全文 Charlie Mathey Cyril Feau Ioannis Politopoulos David Clair Laurent Baillet Michel Fogli 《地震工程与结构动力学》2016,45(15):2455-2474
The present work investigates the influence of small geometrical defects on the behavior of slender rigid blocks. A comprehensive experimental campaign was carried out on one of the shake tables of CEA/Saclay in France. The tested model was a massive steel block with standard manufacturing quality. Release, free oscillations tests as well as shake table tests revealed a non‐negligible out‐of‐plane motion even in the case of apparently plane initial conditions or excitations. This motion exhibits a highly reproducible part for a short duration that was used to calibrate a numerical geometrically asymmetrical model. The stability of this model when subjected to 2000 artificial seismic horizontal bidirectional signals was compared with the stability of a symmetrical one. This study showed that the geometrical imperfections slightly increase the rocking and overturning probabilities for earthquake signals in a narrow range of peak ground acceleration. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Large‐scale, servo‐hydraulic shake tables are a central fixture of many earthquake engineering and structural dynamics laboratories. Wear and component failure from frequent use may lead to control problems resulting in reduced motion fidelity, necessitating repairs and replacement of major components. This paper presents a methodology to evaluate shake table performance pre‐ and post‐repair, including the definition of important performance metrics. The strategy suggested is presented in the context of the rebuilding of a 4.9 × 3.1 m, 350‐kN‐capacity uniaxial shake table. In this case, the rebuild consisted of characterization of wear to table components, replacement of worn bearing surfaces, and replacement of hydraulic accumulators. To assess the effectiveness of the repair actions, sinusoidal and triangular waves, white noise, and earthquake histories were run on the table before and after the rebuild. The repair actions were successful in reducing the position and velocity dependence of friction, improving the ability of control algorithms to accurately reproduce earthquake motions. The maximum and average response spectral misfits in the period range of 0.1–2 seconds were reduced from approximately 50% to 15%, and from 5% to less than 2.5%, respectively. 相似文献
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Real-time hybrid simulation is an efficient and cost-effective dynamic testing technique for performance evaluation of structural systems subjected to earthquake loading with rate-dependent behavior. A loading assembly with multiple actuators is required to impose realistic boundary conditions on physical specimens. However, such a testing system is expected to exhibit significant dynamic coupling of the actuators and suffer from time lags that are associated with the dynamics of the servo-hydraulic system, as well as control-structure interaction (CSI). One approach to reducing experimental errors considers a multi-input, multi-output (MIMO) controller design, yielding accurate reference tracking and noise rejection. In this paper, a framework for multi-axial real-time hybrid simulation (maRTHS) testing is presented. The methodology employs a real-time feedback-feedforward controller for multiple actuators commanded in Cartesian coordinates. Kinematic transformations between actuator space and Cartesian space are derived for all six-degrees-offreedom of the moving platform. Then, a frequency domain identification technique is used to develop an accurate MIMO transfer function of the system. Further, a Cartesian-domain model-based feedforward-feedback controller is implemented for time lag compensation and to increase the robustness of the reference tracking for given model uncertainty. The framework is implemented using the 1/5th-scale Load and Boundary Condition Box (LBCB) located at the University of Illinois at Urbana- Champaign. To demonstrate the efficacy of the proposed methodology, a single-story frame subjected to earthquake loading is tested. One of the columns in the frame is represented physically in the laboratory as a cantilevered steel column. For realtime execution, the numerical substructure, kinematic transformations, and controllers are implemented on a digital signal processor. Results show excellent performance of the maRTHS framework when six-degrees-of-freedom are controlled at the interface between substructures. 相似文献
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Porcelain electrical equipment (PEE), such as current transformers, is critical to power supply systems, but its seismic performance during past earthquakes has not been satisfactory. This paper studies the seismic performance of two typical types of PEE and proposes a damping method for PEE based on multiple tuned mass dampers (MTMD). An MTMD damping device involving three mass units, named a triple tuned mass damper (TTMD), is designed and manufactured. Through shake table tests and finite element analysis, the dynamic characteristics of the PEE are studied and the effectiveness of the MTMD damping method is verified. The adverse influence of MTMD redundant mass to damping efficiency is studied and relevant equations are derived. MTMD robustness is verified through adjusting TTMD control frequencies. The damping effectiveness of TTMD, when the peak ground acceleration far exceeds the design value, is studied. Both shake table tests and finite element analysis indicate that MTMD is effective and robust in attenuating PEE seismic responses. TTMD remains effective when the PGA far exceeds the design value and when control deviations are considered. 相似文献
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Generalised formulation of composite filters and their application to earthquake engineering test systems 下载免费PDF全文
下载免费PDF全文 David Paul Stoten 《地震工程与结构动力学》2017,46(14):2619-2635
This paper addresses the problem of generating unmeasured kinetic data—and/or providing improvements in existing data—for the enhancement of performance characteristics of earthquake engineering test systems, such as shaking tables, reaction walls and other custom‐made test rigs. The approach relies upon the use of composite filters (CF), a method of data fusion that was originally conceived via transfer function formulation. The current work generalises the CF concept and extends its formulation into the state‐space domain, thereby providing a wider basis for application to test systems and their controllers, including those of a multivariable (coupled, multi‐axis) nature. Comparative simulation studies of shaking table control are presented that demonstrate the design techniques for state‐space CF and also their effectiveness for signal synthesis, noise suppression and performance improvement. Specific examples include the use of CF for displacement demand signal generation, velocity feedback generation and acceleration control. In each case, the essential principles behind CF—output signals with zero bias and zero drift—are consistently upheld. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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Vertical earthquake response of megawatt‐sized wind turbine with soil‐structure interaction effects 下载免费PDF全文
下载免费PDF全文 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. 相似文献
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在地震作用下,抗震支吊架理应保障建筑机电工程设施和管道系统均具备良好的服役性能。因此,对抗震支吊架的抗震性能进行检测至关重要。本文以某典型地下室抗震支吊架为对象开展了顺管向地震模拟振动台试验,通过多工况试验对比分析了不同支吊架的位移和加速度的地震响应。试验结果表明:抗震支吊架显著降低了管道位移,减振率最高可达到96%,但对于加速度响应的抑制作用较小。易损性分析表明:采用成品支吊架时,管道系统在遭受相当于设防烈度的地震作用时会发生严重损伤,而采用抗震支吊架的管道系统能够保全其功能。 相似文献
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The overturning fragilities of symmetric and asymmetric freestanding blocks, ranging in height from 0.54 to 3.6 m and with height‐to‐width ratios ranging from 2.1 to 6.6, are determined numerically. A probabilistic formulation regularizes the overturning responses when exposed to earthquake‐like random‐vibration waveforms. The peak amplitude of the forcing excitation (peak ground acceleration or PGA) is parameterized as a function of the block size, block shape, overturning probability, and either the PGA normalized peak ground velocity (PGV/PGA), spectral acceleration at 1 s (Sa(1)/PGA), or spectral acceleration at 2 s (Sa(2)/PGA). These later intensity measures are correlated with the duration of the predominant acceleration pulse. The overturning fragilities are compared with shake table experiments using blocks ranging in height from ～0.2 to 1.2 m and with height‐to‐width ratios ranging from ～2 to 10. Excitations utilized in the shake table experiments include recordings of the 1979 Imperial Valley, 1985 Michoacan, 1999 Duzce, 1999 Chi‐Chi, and 2002 Denali Earthquakes along with synthetic waveforms. The overturning fragilities accurately represent the overturning responses of blocks with simple basal contact conditions. Objects with multiple rocking points, such as precariously balanced rocks, are more fragile than predicted. Nondestructive tilting tests are used to account for blocks with complex basal contact conditions, demonstrating that these blocks overturn similarly to more slender blocks with simple contact conditions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献