风力发电结构动力反应的一体化有限元模型分析

本文通过对风力发电结构系统地震作用下的动力反应的大量研究,提出了一种可用于分析风力发电结构的"桨叶—塔体—基础"一体化有限元模型,并结合土-结构相互作用的分析形成了另一种对比模型。利用上述分析模型对风力发电结构分别进行动力荷载作用下的模态分析和动力时程分析。结果表明,地震作用下考虑土-结构相互作用对风力发电结构动力响应的影响不容忽视,并且可为工程设计提供参考。     

海上风电单桩支撑结构第一自振频率分析研究

目前,海上风电支撑结构一般设计成半柔性结构,为避开风机叶轮激振频率,风电支撑结构第一自振频率处于1倍和3倍的风轮激振频率之内,所以要求设计时能够准确计算风电支撑结构的第一自振频率,避免由共振而带来严重破坏。但海上风机自振频率受整体结构形式、地质环境条件、土-结构相互作用、水附加质量等影响,采用简单模型很难准确得到。为此,本文针对海上风电单桩结构,基于ABAQUS软件建立了整体有限元模型。土体采用有限元-无限元相结合的方式进行模拟、桩-土之间采用接触单元、考虑水附加质量的影响,计算结构的第一自振频率并进行参数敏感性分析。研究表明采用三维有限模型,考虑土-结构相互作用,能够较准确计算海上风电结构第一自振频率,为风电结构设计提供更可靠的设计参数。     

Stochastic seismic response analysis of offshore wind turbine including fluid‐structure‐soil interaction

This paper presents the stochastic seismic response analysis of offshore wind turbines subjected to multi‐support seismic excitation by using a three‐dimensional numerical finite element model considering viscous boundaries. The seawater‐offshore wind turbine‐soil interaction system is modelled by the Lagrangian (displacement‐based) fluid and solid‐quadrilateral‐isoparametric finite elements. The random seismic excitation is described by the filtered white noise model and applied to each support point of the three‐dimensional finite element model of the coupled interaction system. The research conducts a parametric study to estimate the effects of variable seawater level, different foundation soil types and support site conditions on the stochastic behaviour of the offshore wind turbine coupled interaction system. The finite element model of coupled interaction system was also analyzed to examine the effect of the surrounding ice sheet on the stochastic response of the coupled system with and without ice sheet. The results obtained for different cases are compared with each other. Copyright © 2010 John Wiley & Sons, Ltd.     

Influence of soil‐structure interaction on performance of a super tall building using a new eddy‐current tuned mass damper

Tuned mass dampers (TMDs) can be used as vibration control devices to improve the vibration performance of high‐rise buildings. The Shanghai Tower (SHT) is a 632‐m high landmark building in China, featuring a new eddy‐current TMD. Special protective mechanisms have been adopted to prevent excessively large amplitude of the TMD under extreme wind or earthquake loading scenarios. This paper presents a methodology for simulating behavior of the new eddy‐current TMD that features displacement‐dependent damping behavior. The TMD model was built into the SHT finite element model to perform frequency analysis and detailed response analyses under wind and earthquake loads. Furthermore, soil‐structure interaction (SSI) effects on wind and seismic load responses of the SHT model were investigated, as SSI has a significant impact on the vibration performance of high‐rise buildings. It was found that SSI has more significant effects on acceleration response for wind loads with a short return period than for wind loads with a long return period. Some of the acceleration responses with SSI effects exceed design limits of human comfort for wind loads with shorter return periods. As to the seismic analyses, it was found that SSI slightly reduces the displacement amplitude, the damping force, and the impact force of the TMD.     

基于地震荷载作用下的风力发电塔的地震响应分析

基于地震荷载的作用,应用大型有限元软件FINAL,研究不同结构参数的风力发电塔在地震荷载作用下的地震响应,以及比较它们之间的差异,进而得出改变风力发电塔的结构参数对于地震响应的影响规律.以二维风力发电塔模型为例,建立4个不同参数的模型,首先进行模态分析,计算出每个模型的固有频率,通过比较固有频率得出结论,并对其进行比较分析.然后对4个模型施加1993年北海道西南海面桥地震波形,分析比较它们在此地震波形作用下的地震响应值,进而得出不同的结构参数对地震响应的影响规律.     

Wind field simulation and wind‐induced responses of large wind turbine tower‐blade coupled structure

Herein, by a case study on a 5‐MW wind turbine system developed by Nanjing University of Aeronautics and Astronautics, the wind field simulation and wind‐induced vibration characteristics of wind turbine tower‐blade coupled systems is analyzed. First, the blade‐nacelle‐tower‐basis integrated finite element model with centrifugal forces induced by rotational blades is established. Then, based on a harmony superposition method and the modified blade element‐momentum theory, the fluctuating wind field of tower‐blade coupled systems is simulated, which considers wind shear effect, tower shadow effect, rotational effect, blade‐tower dynamic and model interaction effects. Finally, the wind‐induced dynamic responses and wind vibration coefficients of the wind turbine tower‐blade coupled structure are discussed through the ‘consistent coupled method’ previously proposed by us. The results indicate that the wind‐induced responses of a large wind turbine tower‐blade coupled structure present complicated modal responses and multimode coupling effect. Additionally, the rotational effect would amplify aerodynamic loads on blades with high frequency, wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The centrifugal force effect could also amplify natural vibration frequency of the tower‐blade coupled system and reduce the wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The research could contribute to wind‐resistant design of structure for a large‐scale wind turbine tower‐blade system. Copyright © 2014 John Wiley & Sons, Ltd.     

Performance evaluation of an MR damper in building structures considering soil–structure interaction effects

Since the force generated by a magneto‐rheological (MR) damper has large nonlinearity, the performance of an MR damper is dependent on response characteristics such as frequency and amplitude. Soil–structure interaction (SSI) is generally known to have a large effect on the seismic response of a building structure. In this study, the performance of an MR damper in mitigating the seismic response of a building structure is evaluated considering the SSI effects. First, the performance variance of an MR damper due to the change of the structural natural period is investigated by constructing its normalized response spectrum through the numerical analysis of many earthquake wave records and the natural period of a structure. The variable friction force of an MR damper is normalized by the structural base shear force, and its amplitude and decrement of response are quantitatively evaluated. Then, the response characteristics of the SSI system due to the lengthening of the structural natural period and various soil conditions are numerically evaluated based on the response spectrum analysis. Finally, the numerical results with and without considering the SSI effects are comparatively evaluated for the building structure with an MR damper. The comparison results show that the SSI effect should be considered in order that the undesirable effect of an MR damper on the structural control would not be neglected. Copyright © 2007 John Wiley & Sons, Ltd.     

2.5MW海上风力发电机钢塔筒地震响应分析

以福建某海滩单机容量为2.5MW海上风力发电机为原型,应用ABAQUS有限元软件分别建立风力发电塔的地基刚接模型和考虑土与结构相互作用的质量-弹簧-阻尼模型.通过给模型施加地震波,对风力发电塔体系进行地震动力作用时程分析.主要研究了土与结构相互作用（Soil-structure interaction,SSI）对风力发电塔体系地震响应的影响.研究表明,SSI效应降低了风力发电塔的地震应力响应,增加了其地震位移响应.     

Probabilistic seismic demand analysis of a slender RC shear wall considering soil-structure interaction effects

Reinforced concrete shear walls are often used to resist the lateral loads imposed by earthquakes. Accurate evaluation of the seismic demands on shear walls requires adequate considerations of the nonlinear behavior of structural and foundation elements, the interaction between them, and the uncertainty and variability associated with earthquake ground motions. This paper presents a comprehensive probabilistic seismic demand analysis of a typical mid-rise slender shear wall in western US with a flexible foundation and evaluates the significance of soil-structure interaction (SSI) effects on their damage probability. Utilizing realistic numerical models for the shear wall and its foundation, the nonlinear time history analyses were conducted with a large number of recorded ground motions. Response quantities such as maximum inter-story drift ratio, base shear, foundation displacement and rotation are monitored and related to the intensity measure of ground motions (i.e. the inelastic spectral displacement S_di) for the cases with and without considering the SSI effects. Subsequently, the fragility functions of the shear wall are derived and the impact of SSI effects is investigated. It is found that the SSI generally reduces the damage probability of the shear wall, especially when soil nonlinearity is taken into account. The sensitivity of various seismic demands to soil parameters is also discussed. Under strong ground shakings, SSI effects on the maximum inter-story drift are most sensitive to the friction angle of the soil. It is suggested that the damages in foundation and surrounding soil should also be considered in order to systematically evaluate the SSI effects on damage probability of shear wall buildings.     

基于ANSYS的三维自由场地震动反应分析

为探究自由场地震反应的基本规律和考虑土-结构相互作用(SSI)时的整体结构地震反应分析提供参考,采用ANSYS建立了三维自由场有限元模型,分别考虑了同一场地在三种不同水平两向基岩输入地震动以及三种不同类型场地在同一水平两向基岩输入地震动下的两种情况,对其进行了地震反应分析。通过对比和分析得到的各类场地地表中心点的绝对加速度、相对位移、各层土体的层间位移峰值以及绝对加速度峰值等指标,得出一些关于此类问题的有用结论,供工程设计及后续研究时参考。     

锥筒形风机塔架的风致响应分析

用有限元软件Abaqus对近海2.5MW的锥筒形风机塔架结构进行模态分析。通过质量-弹簧-阻尼单元模拟风机塔架的基础,提取它的前八阶模态进行分析。比较塔架固有频率和叶片的旋转频率,发现二者不会发生共振。在模态分析的基础上对风机结构整体进行风致响应分析,验证结构体系的安全性。通过对风机塔架进行风致动力响应分析,为结构的振动特性诊断和预报以及结构动力特性的优化设计提供依据。     

基于流–固耦合的近海风电基础地震反应分析

结合近海风电单桩及四桩基础支撑体系工程实际场地资料,采用有限元数值分析方法,考虑水–土–结构动力相互作用,即考虑流–固耦合效应、饱和土的多孔介质渗流属性及桩–土接触相互作用,分析结构体系动力特性及地震反应。分析单桩有水与无水及四桩有水与无水4种工况支撑体系的自振特性和单桩有水与无水2种工况支撑体系的地震反应。结果表明:水层对结构低阶频率影响不大,对高阶频率降低幅度较大;水层对体系的水平位移、竖向沉降、峰值加速度及有效应力均有不同程度地削减;地震作用下土体的超静孔隙水压力呈现波动特性;结构的位移及应力响应均能满足规范要求。证明考虑多介质耦合的动力有限元分析方法是解决复杂海上风电基础地震响应的有效方法。     

土动力学与岩土地震工程

近年来,随着交通和能源基础设施建设的快速发展,循环动载引起的工程问题使得土动力学与岩土地震工程的研究面临许多新的课题。文章简要评述土动力学与岩土地震工程在国内外的研究现状,着重讨论土的剪切模量、高速铁路路基动力响应及累积沉降、土体地震液化、地下结构地震响应及其抗震设计、跨海桥梁与海上风电基础的动力学问题等方面的最新进展,并进一步阐述今后研究的方向。     

风力发电机组塔架的结构形式及其风载、地震作用综述

风力发电机组的塔架属于高耸结构,承受风荷载和地震作用,可采用钢筒、钢格构、钢筋混凝土筒和钢一混凝土组合筒等多种结构形式。本文简要分析了各种结构形式的优缺点及研究现状,认为随着风力发电机组越来越大型化,钢塔筒面临运输和施工吊装困难。而其它形式的塔架,如钢格构、钢筋混凝土筒和钢一混凝土组合筒塔架,具有易运输、易施工的优点,已获得一定应用,并可能进一步推广。目前,对钢塔筒的研究较多,而对其它形式的塔架研究较少;并且由于叶片数据缺乏,风力发电机组承受的风、地震作用的计算不很准确;此外,研究者分析的风力发电机组数量有限,所得结论不一定具有普遍性。     

SSI效应对隔震结构的地震响应及损伤影响分析

基于弹性地基梁理论和波动理论计算群桩-土地基对上部结构的动力阻抗,进而研究桩土-结构动力相互作用对高层隔震结构地震响应及非线性损伤的影响。首先计算桩周地基水平刚度系数,采用改良的Penzien模型将群桩等效为单桩,考虑一定桩长范围计算桩头的水平刚度,同时根据结构振动频率与地基基本频率的大小关系,考虑地基材料阻尼和辐射阻尼的影响。以某高层隔震工程为例,根据实际桩布置及土层分布情况计算地基阻抗,利用等效线性化模型对结构进行反应谱分析,计算结构隔震前后SSI效应对其动力响应的影响,再利用三维非线性损伤模型分析SSI效应对结构主要构件损伤的影响。计算结果表明,随着结构层数的增加,SSI效应的影响减小,考虑SSI效应会使隔震层位移和隔震支座面压利用率提高,而对隔震层上部结构的层间位移基本没有影响;考虑SSI效应后结构连梁的损伤减小,而框架柱和剪力墙这些竖向构件损伤增加;长周期地震动作用下结构的SSI效应更显著。     

Dynamic characteristics and seismic response of frame–core tube structures,considering soil–structure interactions

In order to study the dynamic characteristics and seismic response of high‐rise buildings with a frame–core tube structure, while considering the effect of soil–structure interactions (SSIs), a series of shaking table tests were conducted on test models with two foundation types: fixed‐base (FB), in which the superstructure was directly affixed to the shaking table, and SSI, consisting of a superstructure, pile foundation, and soil. To increase the applicability of the model to the dynamic characteristics of real‐world tall buildings, the superstructure of test models was built at a scale of 1/50. This simulated a 41‐floor high‐rise building with a frame–core tube structure. The mode shape, natural frequency, damping ratio, acceleration and displacement response, story shear, and dynamic strain were determined in each of the test models under the excitation of simulated minor, moderate, and large earthquakes. The SSI effect on frame–core tubes was analyzed by comparing the results of the two test models. The results show that the dynamic characteristics and seismic response of the two systems were significantly different. Finally, these results were verified by performing a numerical analysis on the differences in the seismic responses of the FB and SSI numerical models under various simulated seismic conditions.     

海上风机的分部与整体结构设计现状

海上风机结构是一个相对复杂的结构系统,其动力响应受到多种环境因素影响,且多种荷载之间的相互作用是一种非线性行为。此外,风力机不同组成部分之间都有其独特特性,结构间的耦合作用决定着风机在非平稳环境力作用下的整体动力反应。分别综述了风机叶片的转动与弹性变形的耦合、塔架与叶片的耦合、塔架的优化设计、基础的模型以及结构随参数变化敏感性分析。最后对未来有待于进一步研究的问题进行介绍。     

Large‐scale shaking table test on pile‐soil‐structure interaction on soft soils

The two large‐scale shaking table tests of tall buildings on soft soils in pile group foundations are performed to capture the effect of the seismic pile‐soil‐structure interaction (PSSI) on the dynamic responses of the pile, soil, and structure. The two different model conditions are observed, including a fixed‐base structure and a structure supported by 3‐by‐3 pile group foundation in soft soil, representing the situations excluding the soil‐structure interaction (SSI) and considering the SSI, respectively. In the tests, the superstructure is a tall building with 12‐story reinforced concrete frame. The pile‐soil‐structure system rests in a shear laminar soil container, which is designed to minimize the boundary effects during shaking table tests. The two models are subjected to various intensity seismic excitations of Shanghai bedrock waves, 1995 Kobe earthquake, and 1999 Chi‐Chi earthquake events. According to the experimental and analytical results, SSI systems have longer natural periods than the fixed‐base structure. In addition, soft soil has amplification effect under smaller seismic excitations and isolation effects under larger earthquake intensities. The strain amplitude at the top of pile is large, and the strain at the middle and tip is relatively small. Whereas the contact pressure is small at the top of pile and large at the middle and tip. From the dynamic responses of the superstructure, it is found that the PSSI amplifies the peak displacements and interstory drifts of the structures supported by pile group foundations by comparing with the fixed‐base structure. Whereas the peak acceleration and interstory shear force of the structure are reduced considering seismic PSSI. The results show that the seismic SSI is not always favorable, however, it may increase certain dynamic responses of the structure. Consequently, the seismic SSI should be considered reasonably, providing insight towards the rational seismic design of buildings rested on soft soils.     

兆瓦级风力发电机塔架的模态分析

通过对内蒙古武川地区水平轴风力机塔架的两种工况进行现场测试,用DASP系统进一步分析,得出塔架的加速度谱及特征频率;利用ANSYS有限元软件完成塔架的建模和模态分析,考虑了塔顶上方机舱总质量的影响。计算结果与实测结果为避免塔架发生共振和进一步研究风力机塔架的动力反应提供了依据,其中模态数据对风电塔架设计和结构振动控制有一定的参考价值。     

Effect of structural nonlinearity on probabilistic risk assessment of offshore wind turbine including inelastic soil medium

This research intends to evaluate the influence of structural nonlinearity on the seismic risk of an offshore wind turbine with respect to linear analysis. The structural nonlinearity is presented into the structure, as materially nonlinear, by calibrating plastic hinge at the end of the elastic beam-element of the structure. To guarantee ideal circumstance for seismic analysis, this study includes inelastic soil stratum by using an equivalent linear approach. Monte Carlo simulation is performed by means of seismic vulnerability of the structural system. The research presents a study of a large amount of simulation over the nonlinear and linear structures considering the random character of basic variables of soil under selective earthquakes. The earthquakes having different source-to-site (STS) distances ranging from 7 to 145?km have consistency with the soil parameters. This rigorous implementation is done to accomplish site-specific dynamic analysis. Illustrative results obtained from nonlinear and linear dynamic analysis are compared. The overall finding shows that the nonlinear structure produces highest estimated uncertainty compared to the linear structure. Another termination can be addressed that the earthquake with less STS distance (7.29?km) causes the highest level of destruction to the structure.