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1.
为了更好满足地震计的振动测试需求,对振动台的波形失真度、横向运动比、台面不均匀度及稳定性等主要性能指标进行了测试分析.测试结果表明:该振动台具有较好的低频振动特性.利用低频标准套组对该振动台和中国计量科学研究院标准振动台进行比对分析,测试结果存在较小偏差. 相似文献
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应泽成 《地震地磁观测与研究》1985,(4)
波形的非线性失真度是评定振动台运动精度的一项重要技术指标,而目前国内外还没有直接测量波形频率低于2Hz的失真度仪,这就限制了低频标准振动台的使用范围,而这正是地震系统及其它一些低频测振系统共同关心的部分。本文提出的超低频波形失真度测量法,是应用FFT方法在频域上展示并量取各次谐波幅值,通过简单计算得出超低频失真度量值。我们已用该方法对中国计量科学院生产的垂直向低频标准振动台和水平向振动台作了频率低于2Hz的失真度量值测试,并获得结果。在国内首次扩大了该套振动装置的使用频率下限,为地震仪及低频测振仪的标定工作作出了贡献。该方法也适用于其它如机电转换装置及电信号发生、记录、转换装置的失真度量值测试。 相似文献
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地震计的校准需低频标准振动台系统产生失真度较低的正弦波,速度反馈广泛用于低频标准振动台系统的失真度降低,然而却会提升整个系统的高频共振峰。为了降低该共振峰,文中提出一种不需要传感器就可以提取振动台加速度信号的技术,并将该信号与速度反馈信号叠加从而降低了该共振峰,然后再通过加大电子阻尼的方法来改善振动台的低频特性。仿真结果表明：加速度反馈可以有效降低整个校准系统的高频共振峰,但反馈量过大会增加低频共振峰,选择合适的参数可以避免低频共振峰的产生。通过加大阻尼进一步降低了振动台的低频下限。最后通过实验验证了复合反馈的作用。为进一步改善电动式振动台的低频失真度,研究低频下限与低频失真度的关系打下一定的基础。 相似文献
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分布式光纤声波传感系统(Distributed Acoustic Sensing, DAS)是近年来迅速发展的新型地震数据采集系统.与传统地震检波器相比,DAS具有耐受恶劣环境,易实现大区域高密度观测等优点.传统地震检波器测量质点速度,而DAS接收沿光纤的轴向应变率(或应变)信号,传统基于速度—应力场弹性波方程全波形反演无法直接用于DAS数据反演.在前人DAS数据全波形反演研究中,将DAS数据转换为沿光纤的质点速度,但会放大低波数噪声,在低信噪比条件下影响反演精度.本文提出了直接基于应变率数据的DAS信号全波形反演方法.首先推导实现了直接基于应变率参数的DAS数据全波形反演理论.其次通过典型模型测试和DAS实测数据验证了直接基于应变率的全波形反演方法在DAS数据速度反演中的可行性和有效性. 相似文献
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DSL—1型流动地震仪是一种多用途微震仪,近年来国内已广泛地应用于天然地震、人工爆破、地面脉动以及工程振动测量等方面。本文详细研究了该系统的动态特性并给出它的解析计算式,以便于对观测波形作定量分析使用。文中还描述对该系统进行的测试研究。结果表明,本文的系统动态特性的理论结果与实验测定吻合良好。 相似文献
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常用的地震传感器有两种,即灵敏的地震计和强运动加速计。它们的名字来自于用于检测运动的传感器、测量速度或位移的地震计和测量加速度的加速度计。 相似文献
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收集了琼中地震台PET重力仪和CTS-1EF地震计在"威马逊""海鸥""莎莉嘉"等3个热带气旋影响期间的观测数据,通过计算获得速度和加速度.比较了热带气旋接近和远离琼中地震台时,重力仪、地震计记录的波形特征,并通过频谱、时频对比,分析重力仪和地震计数据受热带气旋影响的程度.结果表明,在热带气旋影响期间,2台仪器记录数据... 相似文献
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为实现自动检测地震噪声波形是否异常,提出应用BP神经网络技术进行地震噪声波形检测.选取福建地震台网88个测震台站2018-2019年的地震噪声原始波形,计算波形的加速度功率谱密度(PSD)值作为神经网络的输入特征值,在MATLAB中构建BP神经网络进行学习训练和仿真测试.测试验证了训练后的BP神经网络模型具备了可靠的地震噪声波形是否异常的检测能力.应用BP神经网络检测地震噪声波形免去了人工判断的工作,实现全自动处理,提高了检测效率,为今后地震噪声波形质量自动监控提供了新的技术方法. 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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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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The interest in shake tables stems from a need to simulate earthquake behavior in laboratory settings. However, the inherent properties and nonlinearities associated with electromechanical and servohydraulic shake tables, combined with issues of table-structure interaction, make accurate reproduction of earthquake acceleration time histories a challenging problem. The classical approach to control shake tables has been the Transfer Function Iteration (TFI) method. The tuning of the TFI controller is an offline iterative process, conducted using small amplitude ground motions. Effective compensation is not achievable for system nonlinearities that are not projected in the iterative tuning process. To address this problem, researchers have developed online compensation techniques, which can maintain tracking performance for the earthquake signals more effectively. Model-based controllers (MBC) are a class of online controllers which use an identified model of the shake table-structure for compensation. The MBC employs feedforward and feedback controllers to ensure that the shake table tracks a specified earthquake ground motion despite the presence of table and structural nonlinearities. However, the feedback controllers in MBC do not always maintain tracking accuracy and can result in loss of robustness when changes occur in the shake table and structure dynamics. This paper introduces a modified model-based controller (mMBC) for acceleration tracking as an improvement on the existing MBC architecture. A stability condition is introduced to assess the robustness of the new modified control architecture. Through numerical and experimental studies, the improved tracking robustness of the mMBC architecture is demonstrated. 相似文献
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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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Xiang Wang Tara C. Hutchinson Rodrigo Astroza Joel P. Conte José I. Restrepo Matthew S. Hoehler Waldir Ribeiro 《地震工程与结构动力学》2017,46(3):391-407
This paper investigates the seismic performance of a functional traction elevator as part of a full‐scale five‐story building shake table test program. The test building was subjected to a suite of earthquake input motions of increasing intensity, first while the building was isolated at its base and subsequently while it was fixed to the shake table platen. In addition, low‐amplitude white noise base excitation tests were conducted while the elevator system was placed in three different configurations, namely, by varying the vertical location of its cabin and counterweight, to study the acceleration amplifications of the elevator components due to dynamic excitations. During the earthquake tests, detailed observation of the physical damage and operability of the elevator as well as its measured response are reported. Although the cabin and counterweight sustained large accelerations because of impact during these tests, the use of well‐restrained guide shoes demonstrated its effectiveness in preventing the cabin and counterweight from derailment during high‐intensity earthquake shaking. However, differential displacements induced by the building imposed undesirable distortion of the elevator components and their surrounding support structure, which caused damage and inoperability of the elevator doors. It is recommended that these aspects be explicitly considered in elevator seismic design. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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地震预警系统作为一种减轻地震灾害的有效手段,其必须具有两个性能：可靠性和时效性.可靠性要求有低的误报率、漏报率;而时效性要求系统的计算时间短、反应速度快.系统的可靠性和时效性需要反复测试.在特定区域,地震是小概率事件,对于5级以上的破坏性地震更是极其罕见,因此只有通过模拟地震的方式才能对地震预警系统进行有效的测试.目前还没有文献系统地介绍地震预警系统的模拟测试方法.本文提出了振动台模拟、信号发生板卡模拟和软件模拟三种测试方法,并对每种方法的优缺点进行了对比研究.研究表明,软件模拟的优点最多,唯一的缺点是不能测试系统的抗震能力.通过分析,本文建议首先在振动台上做少量几次大幅度地震波输入测试;之后使用软件模拟测试方法,将所有收集到的地震波序列和干扰波形输入地震预警系统,对其进行功能测试,以得到全面且经济的测试效果. 相似文献
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A hypothetical 5‐storey prototype structure with reinforced concrete (RC) frame and unreinforced masonry (URM) wall is considered. The paper focuses on a shake‐table experiment conducted on a substructure of this prototype consisting of the middle bays of its first storey. A test structure is constructed to represent the selected substructure and the relationship between demand parameters of the test structure and those of the prototype structure is established using computational modelling. The dynamic properties of the test structure are determined using a number of preliminary tests before performing the shake‐table experiments. Based on these tests and results obtained from computational modelling of the test structure, the test ground motions and the sequence of shakings are determined. The results of the shake‐table tests in terms of the global and local responses and the effects of the URM infill wall on the structural behaviour and the dynamic properties of the RC test structure are presented. Finally, the test results are compared to analytical ones obtained from further computational modelling of the test structure subjected to the measured shake‐table accelerations. Copyright © 2006 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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A large-scale 20.5 m long asymmetric two-span reinforced concrete bridge was tested to failure using the shake table system
at the University of Nevada Reno. Upon completion of testing, in depth analytical modeling was conducted to evaluate the accuracy
of conventional methods in reproducing the bridge model response and to develop a model for further study. Utilizing the experimentally
verified computer model, the system effect was investigated, comparing the system and response of individual bents as well
as the response of several other bridge models. In comparing computational model of the shake table specimen and models of
the individual bents with tributary mass, it was shown that for all of the columns in this study, there was generally not
an increase in hysteretic energy or large displacement cycles from system response at given displacement demand. The response
of the bents for each high amplitude test motion was also compared. It was shown that there were significant differences in
the bent demands for a given excitation due to system effects. In addition to the shake table model, four bridge systems with
a constant total lateral stiffness were used in a parametric study to determine the system effect. The symmetric and uniform
versions of the bridge specimen were shown to be comparable in nonlinear performance to the bridge specimen for the same high
amplitude demand. The failure progression of the bridge model and the analytical comparisons suggested that the reserve capacity
from varied column heights could provide a beneficial substructure redundancy. 相似文献
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This paper presents a detailed study on feasibility of un‐bonded fiber reinforced elastomeric isolator (U‐FREI) as an alternative to steel reinforced elastomeric isolator (SREI) for seismic isolation of un‐reinforced masonry buildings. Un‐reinforced masonry buildings are inherently vulnerable under seismic excitation, and U‐FREIs are used for seismic isolation of such buildings in the present study. Shake table testing of a base isolated two storey un‐reinforced masonry building model subjected to four prescribed input excitations is carried out to ascertain its effectiveness in controlling seismic response. To compare the performance of U‐FREI, same building is placed directly on the shake table without isolator, and fixed base (FB) condition is simulated by restraining the base of the building with the shake table. Dynamic response characteristic of base isolated (BI) masonry building subjected to different intensities of input earthquakes is compared with the response of the same building without base isolation system. Acceleration response amplification and peak response values of test model with and without base isolation system are compared for different intensities of table acceleration. Distribution of shear forces and moment along the height of the structure and response time histories indicates significant reduction of dynamic responses of the structure with U‐FREI system. This study clearly demonstrates the improved seismic performance of un‐reinforced masonry building model supported on U‐FREIs under the action of considered ground motions. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献