厂房动力特性测试及加固效果评估

介绍了对某生产厂房的动力特性现场测试和对厂房结构的模态分析及谐响应分析结果。在掌握该厂房振动规律的基础上，针对厂房结构的特点提出增设钢斜撑的方法进行加固处理。并用有限元方法进行了计算分析和加固效果评估。     

破碎机引起的钢-混凝土混合结构工业厂房振动测试与治理

某工矿企业破碎筛分车间为钢-混凝土混合结构厂房,布置有9台破碎机,且破碎机基础与主厂房结构没有脱开.破碎机的工作扰力导致结构振动严重.利用吊车冲击和地脉动现场实测了结构动力特性参数,而后测试了破碎机不同开启工况下的结构整体和设备基础的振动线位移,根据实测值评估了厂房的振动安全性.采用ANSYS(R)程序建立有限元模型,进行模态分析和谐响应分析,并与实测结果进行对比分析,以验证有限元模型的准确性,再预测破碎机改造后的结构振动位移大小.改造两台破碎机后再次进行了结构振动现场实测,改造后结构振动明显减小,测试结果与有限元预测结果基本一致.本文的振动测试和治理方法可以为类似工业建筑振动超限问题提供参考.     

某筛分楼振动测试及振动控制研究

多层工业厂房引进大型动力设备而引起的结构振动时有发生。为了研究动力设备扰力作用下结构振动问题,结合某筛分楼在振动筛工作时厂房振动强烈的工程实例,通过现场振动测试和有限元软件Sap2000建模分析,对比理论分析结果与振动测试结果,验证了模型的合理性并确定振动原因。在有限元分析的基础上提出二次隔振加固方案,加固前后的理论计算值对比表明:二次隔振方案减振效果显著,可为既有结构异常振动的减振加固提供一定参考。     

拱形波纹钢屋盖动力特性测试及分析

拱形波纹钢屋盖是一种新颖的金属拱形薄壳结构，在我国已经得到了广泛的应用。由于结构的复杂性，目前有关的理论研究尚不够深入，动力研究还很少有人涉及。以18m和30m两种跨度的W666型拱形波纹钢屋盖为研究对象，测试了拱在竖向平面内振动时的频率、振型及阻尼。在所提简化计算模型的基础上，采用有限元方法计算了结构的动力特性，其结果与试验数据符合较好。测试和分析结果为该结构的动力反应研究提供了方便。     

Earthquake Response Analysis of Soil-reactor Plant-nuclear power Auxiliary Plant Interaction System

土-结构相互作用分析是核电结构抗震设计的重要环节,考虑到附属厂房可能导致反应堆厂房处于最不利工况状态,对地基土-反应堆厂房-核电辅助厂房结构相互作用体系地震响应进行研究。基于PASSI算法,提出显-隐式单元层计算方法,实现显、隐式交替计算,保持高效性的同时,提高计算稳定性。通过场地分析算例和土-结构相互作用分析算例,与ABAQUS软件计算结果进行对比,验证计算方法的可行性。以某核电站为对象,分析同一基础上相邻厂房对反应堆厂房地震响应的影响。研究结果表明,在基岩场地上,安全厂房通过基础和场地对反应堆厂房的作用较小,对反应堆厂房地震响应的影响较小;地震动输入下,燃料厂房和电器厂房加大了反应堆厂房位移峰值,减小了反应堆厂房加速度反应谱峰值,并使反应堆厂房顶部点加速度反应谱峰值向高频移动;与反应堆厂房共用同一基础的辅助厂房,应与反应堆厂房作为整体进行地震响应分析,至少应将与反应堆厂房相连的辅助厂房作为整体进行分析。     

某隔震结构动力特性的理论分析与脉动测试

本文针对国内最大单体隔震建筑建立了SAP2000三维分析模型,并进行了动力特性的理论分析;现场对实际建筑进行了平移振动、扭转振动、垂直振动和平面内弯曲4个方面的脉动测试。利用工程振动反演理论分析了该结构的固有频率、振型、阻尼等动力特性,将实测结构动力特性与理论分析结果进行比较,详细分析实测结果与理论结果差别的原因,并据此对理论模型进行修正,为今后类似结构的设计积累了资料。     

局部复杂场地条件对核电结构自振特性的影响分析

自振特征是核电厂结构动力分析首先应考虑的因素,它也是影响核电厂反应谱特征的关键因素之一。采用常规的自振特性分析方法(如Lanczos法等)只能以核电厂上部结构为模型进行计算求其固有频率,在复杂场地条件下,这样的计算结果通常与更符合实际的土-结构相互作用(SSI)模型计算结果存在较大差异。本文以SASSI用户手册中的典型压水堆核电厂土-结构动力相互作用模型为研究对象,采用时域显式有限元法结合透射人工边界方法及相应编写的三维显式有限元程序3DSSI,计算了同一上部结构,结合多工况局部复杂场地条件的核电厂SSI体系的单脉冲响应,并通过求传递函数幅值谱方法,获得各种工况下SSI体系的自振频率。依据计算结果,分别研究了核电厂上部结构、自由场及SSI体系的自振特征及其相互联系,并通过比较研究,讨论了局部复杂场地特性对核电厂SSI体系自振特性影响等问题,进而加深了对核电厂动力特征及动力安全区性的认知。     

无伸缩缝桥梁的动力特性计算与试验研究

福建省永春县上坂大桥是目前我国修建桥长最大，采用整体式桥台的无伸缩缝桥梁。本文通过该桥的动力试验研究了该桥在天然脉动荷载作用下的自振特性，采用结构分析软件ANSYS建立全桥的空间模型，计算该桥的自振特性，与实测结果进行了分析比较。实桥试验还测试了无障碍行车试验和跳车试验这2种车辆激振作用下桥梁的强迫振动特性，并把实测的荷载冲击系数与新桥规的计算结果进行比较。研究结果有助于对该类桥梁动力特性的认识，有利于进一步开展无伸缩缝桥梁的抗震性能研究。     

工业厂房自振特性的研究

为了积累工业厂房的设备振动资料,给抗震设计提供数据,本文介绍了一座四层楼面粉加工厂房的设备振动及邻近自由地表脉动观测结果,并计算了结构的频率和振型。     

大型双槽渡槽结构振动特性分析

根据大型双槽渡槽的结构特点，应用薄壁梁段有限元法，考虑了渡槽横向弯扭耦合振动、约束扭转变形和盆式橡胶支座等对渡槽结构动力作用的影响；对实际工程中某大型渡槽进行了振动特性分析，研究了该渡槽设计水位变化对大型渡槽模态的影响，探讨了该大型渡槽在几种工况下的模态变化范围，所得结果可为该大型渡槽的抗震设计提供依据。     

Dynamic finite element model updating of prestressed concrete continuous box-girder bridge

The dynamic finite element model(FEM) of a prestressed concrete continuous box-girder bridge,called the Tongyang Canal Bridge,is built and updated based on the results of ambient vibration testing(AVT)using a real-coded accelerating genetic algorithm(RAGA).The objective functions are defined based on natural frequency and modal assurance criterion(MAC) metrics to evaluate the updated FEM.Two objective functions are defined to fully account for the relative errors and standard deviations of the natural fr...     

测定堆石体密度的附加质量法理论分析研究

附加质量法是一种新兴的堆石体密度检测方法,它具有方便、无损等优点,近年来有较为广泛的应用,但该方法的应用效果会受到震源、雨水、双峰频谱等因素的影响.本文则考虑堆石体系统振动的阻尼因素,以及附加质量块与堆石体之间的非刚性连接,分别基于质弹阻模型以及双自由度-质弹阻模型对这些因素的影响进行了理论分析.结果表明,质弹阻模型可以解释主频随震源频率和雨水而变化的现象;而双自由度-质弹阻模型则可以解释主频随质量块偏移距和触地面积而变化的现象.在此基础上,本文对附加质量法的测试过程提出了几点改进建议.     

Errors in response calculations for extensional vibrations of bars

The transient extensional vibrations of a slender and uniform bar, which is clamped at one end and is subjected to an axial force at the other free end, are investigated by applying three methods: the Laplace transform method, the normal mode and Newmark β methods in conjunction with the finite element method (FEM); the errors caused by the spatial discretization of the FEM and the direct integration of the Newmark β method are studied and compared with those of the previous paper where the flexural vibrations of a cantilever beam were considered. The reason why the extensional vibration problem is investigated here is that the condition seems to be severe due to the closeness of adjacent natural frequencies, the larger values of natural frequencies and the smaller number of nodal variables of the FEM in comparison with those of the flexural vibration problem. The numerical results show that the errors in response of the extensional vibration problem are large. However, if one follows the criterion proposed in this paper, accurate response is obtainable by the Newmark β method, which requires less computer time than either of the other methods mentioned above.     

Mode analysis of structures using the Fourier p-element method

The Fourier p-element method is an improvement to the finite element method, and is particularly suitable for vibration analysis due to the well-behaved Fourier series. In this paper, an iteration procedure is presented for solving the resulting nonlinear eigenvalue problem. Three types of Fourier version shape functions are constructed for analyzing the circular shaft torsional vibration, the plate in-plane vibration and annular plate flexural vibration modes, respectively.The numerical results show that this method can achieve higher accuracy and converge much faster than the FEM based on polynomial interpolation, especially for higher mode analysis.     

大跨度预应力混凝土连续刚构桥的动力特性分析

介绍了福建泉州后渚大桥——大跨度预应力混凝土连续刚构桥的现场环境振动实验．并利用频域中的单模态识别法(SDOFI)、峰值法(PP)和时域中的随机子空间识别法(SSI)分别进行桥梁动力特性识别。利用ANSYS建立了全桥三维有限元模型并进行了理论模态分析,基于参数分析和环境振动测试结果对有限元模型进行了标定,建立了该桥的基准有限元模型,该模型可服务于桥梁长期健康监测与状态评估。     

Dynamic 3-D soil–railway track interaction by BEM–FEM

A study on the dynamic response of a railway track is presented via a 3-D formulation based on the frequency domain Boundary Element Method (BEM) and the Finite Element Method (FEM). The railway track consists of a group of surface, massive, rigid footings resting on a viscoelastic half-space and connected by an overlaying rail structure. The BEM, employing the full-space fundamental solutions and quadrilateral elements, is used for the simulation of the elastic half-space while the FEM is used to model the rigid footings and the rail superstructure. The loading function consists of a set of externally applied, harmonic or transient loads. Frequency as well as transient, by way of FFT, results are presented for various modes of vibration. Various numerical studies assess the through-the-soil interaction of the adjacent footings, the influence of soil damping, the effect of the overlaying structure on the frequency content of the system, and the effective simulation of an infinitely long railway track by a truncated one.     

双线地铁运营隔振沟屏障性能研究

为研究双线地铁运营时隔振沟的减振效果,基于2.5维有限元法建立双线地铁列车-轨道-地基土体耦合分析模型。模型克服现有研究将轨道结构简化为弹性地基欧拉梁的缺陷,引入实际钢轨动力学参数,实现双线地铁列车荷载下隔振沟对周围地基的隔振效果分析,比较空沟、填充沟两种不同隔振措施的减振特性,并对填充沟隔振影响因素进行系统的参数分析。研究结果表明:双线运营地铁荷载下,空沟隔振作用体现在沟后范围内,填充沟减振范围更广且效果更好,相比空沟更具工程实用性;填充沟在沟深较小时也能发挥良好的减振作用,增大沟深、沟宽均可有效提高减振效果。研究成果可为今后双线地铁隔振设计与施工提供有益参考。     

Active vibration control of functionally graded beams with piezoelectric layers based on higher order shear deformation theory

This paper reports on a study of active vibration control of functionally graded beams with upper and lower surface-bonded piezoelectric layers. The model is based on higher-order shear deformation theory and implemented using the finite element method (FEM). The proprieties of the functionally graded beam (FGB) are graded along the thickness direction. The piezoelectric actuator provides a damping effect on the FGB by means of a velocity feedback control algorithm. A Matlab program has been developed for the FGB model and compared with ANSYS APDL. Using Newmark’s method numerical solutions are obtained for the dynamic equations of FGB with piezoelectric layers. Numerical results show the effects of the constituent volume fraction and the influence the feedback control gain on the frequency and dynamic response of FGBs.     

Seismic response analysis of an irregular base isolated building

This paper assesses the reliability of code-compliant linear and nonlinear dynamic analyses for irregular buildings with base isolation system (BIS). Comprehensive analyses are carried out for a case study comprising a large reinforced concrete multi-storey framed hospital with 327 high-damping rubber bearings. Spectral and time history (linear and nonlinear) analyses were performed on the three-dimensional (3D) finite element model (FEM) of the structure; simplified analyses were also conducted on single-degree-of-freedom (SDOF) systems. It is found that, at damageability limit state, the values of maximum interstorey drifts (d/h) computed with spectral analyses on the three-dimensional FEM range between 1/6 and 1/10 of the code limit (d/h = 0.33%); thus more stringent code limits should be required for buildings with BISs. The maximum floor acceleration is reduced by about 70% with respect to the ground acceleration (free field site); the acceleration profile is uniform along the height of the multi-storey frame. Threshold values of floor accelerations to assess the seismic performance of equipments in buildings with BIS are lacking. At ultimate limit state (ULS), spectral analyses provide values of actions and deformations that are less conservative than those derived through time history analyses. To perform reliable dynamic analyses of base isolated buildings it is crucial to select natural earthquake ground motions compliant with the fundamental period of vibration of the structural system. Nevertheless, it is not straightforward to select adequate natural strong motions in the catalogues available world-wide; buildings incorporating BISs possess periods of vibration which are generally higher than 2.0 s. As a result, distant and high-magnitude earthquakes are effective for base isolated buildings; nevertheless, such earthquakes are scarce in the seismic databases. The outcomes of the present study also demonstrate that simplified linear analyses tend to provide estimates of the response quantities, displacements of base isolators and base shear of the superstructure, which can be reliably employed at preliminary design stage. Spectral analysis results of the 3D model tend to match those of the SDOF systems, even for irregular superstructure, provided that modal mass participating ratios are greater than 85–90%. The results of spectral analyses on both SDOF and three-dimensional FEM envelope the outcomes of linear time histories.     

高温气冷堆核电厂建筑结构采用不同有限元模型的模态分析对比研究

建立有限元模型是核电厂建筑结构模态分析的重要前提。本文以某高温气冷堆核电厂建筑结构为原型，在分析方法相同的前提下，建立2种不同模型（Solid模型和Shell模型），并对这2种模型进行模态分析。重点分析、对比2种模型的自振频率和振型图，计算分析表明:Solid模型与Shell模型相比，计算得到的结构自振频率值较高，但两者的差异很小，前30阶自振频率相对误差小于3.4%；2种模型的计算结构振型基本一致。研究结果可为核电厂抗震性能分析和设计提供参考。