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基于现场实测风机桥架振动响应,采用风机调幅扰力模型进行结构动力响应分析.根据不同工况下疲劳危险点的名义应力时程,采用雨流计数法和各工况年运行频次调查结果编制疲劳载荷谱.通过Miner损伤累积准则和p-S-N关系对风机桥架进行疲劳损伤分析,给定疲劳破坏的损伤阈值,所得疲劳寿命满足设计使用年限的要求.采用Goodman、Gerber和Soderberg模型考虑平均应力影响时的疲劳寿命略有降低. 相似文献
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地幔对流在岩石圈底部产生的剪切拖曳力和应变率的估计有助于理解和认识板块构造运动、岩石圈变形特征和应力分布格局、地壳长期运动状态和克拉通演化的深部动力学环境,但准确地估计它们是一个挑战.本文利用核相剪切波分裂各向异性约束下获得的全球和区域地震速度结构"耦合"的地幔对流模型计算了中国大陆岩石圈底部的剪切拖曳力和应变率.结果表明,与地幔对流速度相比,剪切拖曳力和应变率具有更加复杂的分布格局;剪切拖曳力的大小位于前人估计的范围之内,但其最大值明显较小,不超过4.0 MPa.中国西部的剪切拖曳力明显大于东部;剪切应变率不超过45/100 Ma;地幔黏度的横向变化可能会导致剪切拖曳力与剪切应变率呈负相关关系. 相似文献
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九江地震台洞体应变观测环境影响分析 总被引：1，自引：1，他引：0
对九江地震台2008—2013年洞体温度年变化、气压上升、集中降雨、抽水和承压含水层卸载对洞体应变产生的异常进行统计,获得应变异常量级范围,建立洞体应变观测简单静力学模型。研究认为,九江地震台山洞线应变年变化由观测基线介质的温度效应引起,而气压、降雨、抽水和含水层卸载引起的应变变化则主要由山体附加应力决定。 相似文献
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桩基静载试验与高应变对比分析 总被引：3，自引：0，他引：3
桩基承载力对桩基抗震性能有很大影响。通过对大量的桩基静载荷试验和同一根桩上的高应变的对比研究，总结了高应变测试极限承载力的准确性与可靠性，分析了引起高应变测试结果误差的原因，提出了消除高应变测试误差的一些方法和注意事项。 相似文献
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针对唐山等大地震前出现的形变空区现象，依据实验和理论对应变空区进行了探讨． 实验过程中采用焦散线法、实时全息干涉计量方法(激光)图像摄影记录，同时进行微破裂(声发射)记录．依据固体损伤理论，结合微破裂定位对应变空区进行研究，得出两点结论:①应变空区在线弹性情况下出现是一种必然现象，且应变空区的位置相对稳定，与裂纹端部的应力集中相对应；②应变空区内几乎不发生微破裂．微破裂总是从高应力区产生，且几乎就发生在应力集中区与应变空区相联的条带内，最终表现为微破裂(声发射)的带状或成丛分布．主破裂总是从应变核(焦散阴影区)开始，然后向应变空区急剧发展，形成主大破裂，最终导致试样崩溃． 相似文献
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工业建筑中,由于工艺的需要常布置大量的动力设备,且动力设备与结构相连。某火力发电厂的重要结构,在其钢平台上布置有64台直径为9.14 m的低频运转风机,风机运转频率与结构基频接近。试验设计了该结构包括风机的1/4模型,首先进行动力特性测试,再按照不同工况使风机群按照不同频率运转,测试结构的振动位移反应。分析认为,虽然风机运转引起的结构振动位移绝对值不大,但该动力位移是结构正常工作时频繁出现的,应注意结构的疲劳破坏;风机低频运转对结构的影响要大于高频运转对结构的影响,在实际工程中,风机运转频率接近结构前三阶频率时应跨越。 相似文献
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将钻孔体应变仪与分量式应变仪的观测资料在面应变平台上进行整合,对于解决目前两种应变仪观测数据的评估、分析、处理和地震预报问题有实际意义．根据潘立宙-陈沅俊和Evertson理论及弹性力学知识,分别建立了平面应力作用下体应变和面应变观测的力学模型,推导了观测钻孔、空孔和无孔岩石体应变与面应变转换系数的计算公式,发现它们都可以归结为同一公式描述,差异仅在于k（体应变仪钢筒内壁或无孔岩石面应变与空孔岩石面应变之比）的取值不同．用Evertson理论推导的公式与空孔岩石情形相近,当岩石弹性模量为4times;1010——8times;1010 Pa时,二者都可以看成是对潘-陈公式的一种简化、近似计算;无孔岩石的情况则相当于在岩石弹性模量为1times;1010 Pa时对该式的一种估计. 文中结合实际情况对转换系数的各种影响因素进行了详细分析． 相似文献
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Experimental implementation and verification of multi‐degrees‐of‐freedom effective force testing 
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下载免费PDF全文 This paper presents an experimental implementation and verification of multi‐degrees‐of‐freedom effective force testing (MDOF‐EFT). An experimental setup that consists of a two‐degrees‐of‐freedom structural system and two hydraulic actuators at the Johns Hopkins University was utilized in this study. First, experimental system identification was performed to develop compatible analytical models for the multi‐input and multi‐output systems. Dynamics of the control plant, that is, the valve‐to‐force relations, were modeled with a rational polynomial transfer function matrix and delay components. By using the analytical model, a centralized decoupling loop‐shaping force feedback controller was designed such that the forces are uncoupled and the loop transfer functions have desirable dynamic characteristics in the frequency domain. Then, a series of harmonic force and earthquake simulation tests were performed to assess capabilities and limitations of MDOF‐EFT. Experimental results showed that the dynamic forces in the two actuators were accurately controlled to provide tracking while the system was stable and robust for the entire period of the experiment. Furthermore, earthquake simulation tests with increased levels of the reference forces demonstrated the feasibility of MDOF‐EFT with highly nonlinear test structures. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Real‐time force control for servo‐hydraulic actuator systems using adaptive time series compensator and compliance springs 下载免费PDF全文
下载免费PDF全文 《地震工程与结构动力学》2018,47(4):854-871
Servo‐hydraulic actuators have been widely used for experimental studies in engineering. They can be controlled in either displacement or force control mode depending on the purpose of a test. It is necessary to control the actuators in real time when the rate‐dependency effect of a test specimen needs to be accounted for under dynamic loads. Real‐time hybrid simulation (RTHS) and effective force testing (EFT) method, which can consider the rate‐dependency effect, have been known as viable alternatives to the shake table testing method. Due to the lack of knowledge in real‐time force control, however, the structures that can be tested with RTHS and EFT are fairly limited. For instance, satisfying the force boundary condition for axially stiff members is a challenging task in RTHS, while EFT has a difficulty to be implemented for nonlinear structures. In order to resolve these issues, this paper introduces new real‐time force control methods utilizing the adaptive time series (ATS) compensator and compliance springs. Unlike existing methods, the proposed force control methods do not require the structural modeling of a test structure, making it easy to be implemented especially for nonlinear structures. The force tracking performance of the proposed methods is evaluated for a small‐scale steel mass block system with a magneto‐rheological damper subjected to various target forces. Accuracy, time delay, and resonance response of these methods are discussed along with their force control performance for an axially stiff member. Overall, a satisfactory force tracking performance was observed by using the proposed force control methods. 相似文献
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Sung-Ryul Kim Oh-Soon Kwon Myoung-Mo Kim 《Soil Dynamics and Earthquake Engineering》2004,24(11):853-866
In the analysis of the seismic stability of gravity type quay walls, the magnitudes of force components acting on quay walls during earthquakes and the phase relationships among these force components must be properly evaluated. In general, the force components include inertia force of the wall, lateral earth force, and water force. The magnitude and the phase relationship of each force component vary with time, and are largely affected by the magnitude of excess pore pressure developed in the backfill soil of the quay wall. The dynamic thrust develops at the contact surface between the backfill soil and the wall as a result of the interaction among these force components. In this study, a simple model is proposed to evaluate the magnitude and the phase variation of the dynamic thrust on the back of the wall. The proposed model computes the dynamic thrust by using the force components calculated from existing equations. We verified the proposed model by comparing its results with those obtained from a series of shaking table tests. 相似文献
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Equivalent force control method for substructure pseudo‐dynamic test of a full‐scale masonry structure 下载免费PDF全文
下载免费PDF全文 Zaixian Chen Guoshan Xu Bin Wu Yongtao Sun Huanding Wang Fenglai Wang 《地震工程与结构动力学》2014,43(7):969-983
The effectiveness of equivalent force control (EFC) method has been experimentally validated through hybrid tests with simple specimens. In this paper, the EFC method is applied for the MDOF pseudo‐dynamic substructure tests in which a three‐storey frame‐supported reinforced concrete masonry shear wall with full scale is chosen as physical substructure. The effects of equivalent force controller parameters on the response performance are studied. Analytical expressions for the controller parameter ranges are derived to avoid response overshooting or oscillation and are verified by numerical simulation. The controller parameters are determined based on analytical and numerical studies and used in the actual full‐scale pseudo‐dynamic test. The test results show good tracking performance of EFC, which indicates a successful test. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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随着地下空间大规模开发利用,地震灾害对其造成的潜在威胁不容忽视。基于《城市轨道交通结构抗震设计规范(GB50909-2014)》和《地下铁道建筑结构抗震设计规范(DG/TJ08-2064-2009)》建议的分析方法,选取惯性力法、反应位移法(国家规范法、上海规范法)、动力时程方法(线弹性方法、等效线性化方法)三类共5种计算方法,以典型两层双柱三跨地铁车站结构为分析对象进行地震反应的对比验算,对上述计算方法的适应性进行评价。分析结果表明,与动力时程方法相比较,惯性力法计算得到的侧墙剪力值偏大,中柱结果较为接近;对于反应位移法,国家规范方法和上海规范方法的计算模型略有不同,但两者计算结果基本相近,其中土体强制位移、集中地基弹簧、土体动剪切模量等参数取值对计算结果影响显著;对于动力时程方法,线弹性方法和等效线性化方法的结果较为接近,且变化趋势相同。 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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Mettupalayam V. Sivaselvan Andrei M. Reinhorn Xiaoyun Shao Scot Weinreber 《地震工程与结构动力学》2008,37(15):1785-1800
A new approach to dynamic force control of mechanical systems, applicable in particular to frame structures, over frequency ranges spanning their resonant frequencies is presented. This approach is implemented using added compliance and displacement compensation. Hydraulic actuators are inherently velocity sources, that is, an electrical signal regulates their velocity response. Such systems are therefore by nature high‐impedance (mechanically stiff) systems. In contrast, for force control, a force source is required. Such a system logically would have to be a low‐impedance (mechanically compliant) system. This is achieved by intentionally introducing a flexible mechanism between the actuator and the structure to be excited. In addition, in order to obtain force control over frequencies spanning the structure's resonant frequency, a displacement compensation feedback loop is needed. The actuator itself operates in closed‐loop displacement control. The theoretical motivation, as well as the laboratory implementation of the above approach is discussed along with experimental results. Having achieved a means of dynamic force control, it can be applied to various experimental seismic simulation techniques such as the effective force method and the real‐time dynamic hybrid testing method. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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We present laboratory and field evidence that in mountainous catchment‐fan systems persistent alluvial fanhead aggradation and trenching may result from infrequent, large sediment inputs. We suggest that the river‐fan systems along the fault‐bounded range front of the western Southern Alps, New Zealand, are likely to be in a dynamic equilibrium on ≥103‐yr timescales, superimposed on which their fanheads undergo long‐term cumulative episodic aggradation. These fanheads are active only in rare events, do not take part in the usual behaviour of the catchment‐fan system and require much longer to exhibit dynamic equilibrium than the rest of the fan. These findings (1) increase our knowledge of the effects of extreme events on alluvial fan morphodynamics in humid climates, (2) question the general applicability of inferring past climatic or tectonic regimes from alluvial‐fan morphology and stratigraphy and (3) provide a conceptual basis for hazard zonation on alluvial fans. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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In order to study the dynamic performance of seismically isolated bridges under the most unfavorable loads in the longitudinal direction,a dynamic equation for vehicle braking in the longitudinal direction is established.A four or fiveorder Runge-Kutta method is adopted to obtain the time-history response of a wheel set under braking force.The quadratic discretization method is then used to transform this time-history into a braking and bending force time-history of a structural fixed node,and a dynamic response analysis of the seismically isolated bridge under the vehicle’s braking force is carried out using ANSYS,a universal finite element analysis software.According to the results,seismic isolation design results in a more rational distribution of braking force among piers;the influence of the initial braking velocity on the vehicle braking force is negligible;the location where the first wheel set leaves the bridge is the most unfavorable parking location;a seismic isolation bridge bearing constructed according to typical design methods enters into a yield stage under the braking force, while the shearing force at the bottom of the pier declines as the isolation period is extended;the design requirements can be met when the yield displacement of the seismic isolation bearing is less than 5 mm and the yield strength is greater than the braking force. 相似文献
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土钉支护体系作为一种经济、有效的支护方式而得到广泛的应用。但关于土钉力计算的理论依然相对缺乏,远远落后于工程实践,严重制约了土钉技术的发展。基于杨光华提出的土钉力简化计算方法[1],以4种不同的土压力模式为背景进行简化,并对比分析不同土压力模式下的土钉力分布,结果表明:采用根据侧壁主动土压力与总土钉力相等并考虑施工过程的影响和增量法的土钉力简化计算方法简便,且采用三角形土压力分布模式与梯形土压力分布模式(二)较采用其他两种土压力分布模式简化计算得到的结果与监测结果更接近。 相似文献