Improving the wind‐induced human comfort of the Beijing Olympic Tower by a double‐stage pendulum tuned mass damper

With five sub towers and a maximum height of 246.8 m, the Beijing Olympic Tower (BOT) is a landmark of Beijing. The complex structural properties and slenderness of the BOT render it prone to wind loading. As far as the wind‐induced performance of this structure is concerned, this paper thus aims at a tuned mass damper‐based mitigation system for controlling the wind‐induced acceleration response of the BOT. To this end, the three‐dimensional wind loading of various wind directions are simulated based on the fluctuating wind force obtained by the wind tunnel test, by which the wind‐induced vibration is evaluated in the time domain by using the finite element model. A double‐stage pendulum tuned mass damper (DPTMD), which is capable of controlling the long period dynamic response and requires only a limited space of installation, is optimally designed at the upper part of the tower. Finally, the wind‐induced response of the structure with and without DPTMD is compared with respect to various wind directions and in both the time and frequency domains. The comparative results show that the wind‐induced accelerations atop the tower with the wind directions of 45, 135, 225, and 315° are larger than those with the other directions. The DPTMD significantly reduces the wind‐induced response by the maximum acceleration reduction ratio of 30.05%. Moreover, it is revealed that the control effect varies noticeably for the five sub towers, depending on the connection rigidity between Tower1 and each sub tower.     

考虑桨叶旋转效应的海上风力发电高塔系统随机风振响应与动力可靠度分析

研究了考虑桨叶旋转效应的海上风力发电高塔系统随机动力响应与风振可靠度分析.在风场模拟中,桨叶风荷载需要考虑旋转效应的影响.因此,对塔体风荷载,直接采用基于物理机制的随机Fourier谱,而对桨叶风荷载,则采用考虑桨叶旋转机制的随机Fourier谱概念.在此基础上,结合概率密度演化理论,对海上风力发电高塔系统进行了随机动力响应分析以及基于塔顶位移响应的风振动力可靠度分析.结果表明,上述方法能够有效地进行此类结构的随机动力响应及可靠度分析.     

Tuned liquid column dampers in offshore wind turbines for structural control

With offshore wind turbines becoming larger, being moved out further at sea and subjected to ever greater wind and wave forces, it is necessary to analyse the dynamics and minimise the responses of these structures. In this paper, the structural responses of offshore wind turbines are simulated with an attached damper (Tuned Liquid Column Damper (TLCD)) for controlling the vibrations induced within the structure. This requires a realistic simulation of the forces that these tall, flexible and slender structures are subjected to, and consequently the implementation of a damper to control the resulting undesirable vibrations that are induced within the structure. Since sea waves are caused by wind blowing for a sufficiently long time, the state of the sea is related to wind parameters and there exists the possibility of correlating wind and wave loading conditions on structures. The Kaimal spectrum for wind loading is combined with the JONSWAP wave spectrum to formulate correlated wind and wave loadings. The offshore turbine tower is modelled as a Multi-Degree-of-Freedom (MDOF) structure. Cases for flat sea conditions, with which parallels to onshore wind turbines may be drawn, are first simulated. Simulations are presented for the MDOF structure subjected to both ‘moderate’ and ‘strong’ wind and wave loadings. Cases of the blades lumped at the nacelle along with rotating blades are investigated. The reduction in bending moments and structural displacement response with TLCDs for each case are examined. A fatigue analysis is carried out and the implementation of TLCDs is seen to enhance the fatigue life of the structure. An analysis, taking into account the extended fatigue life and reduced bending moments on the structure-TLCD system, is presented.     

特高压大跨越输电塔动力特性和风振响应分析

针对特高压大跨越输电塔跨越档距大、塔体高且负荷重的特点,从材料选取、导线排列方式、结构动力特性以及风振响应等几个方面对1 000 kV特高压双回路跨越输电塔进行分析,总结了所研究塔型的动力特点,对其风振系数进行了计算和讨论,并根据动力特性分析提出了结构设计中风振系数的取值方法。结果表明:风振系数具有较大的离散性,不同塔身高度应取不同的值进行计算;该方法为特高压大跨越输电塔的结构设计提供了参考。     

特高压输电线路动态风偏响应及参数影响分析

输电线路风偏响应与线路结构参数密切相关,研究特高压输电线路的风偏响应规律有助于防范闪络事故的发生。通过风洞试验测定特高压输电线路八分裂导线和绝缘子串的气动力参数。建立连续多跨特高压输电线路风偏响应分析的两阶段频域法,即先以非线性有限元静力计算确定平均风作用下的导线静态风偏响应,随后以该状态下导线的构型和刚度为初始条件,引入考虑面内振型影响的气动阻尼,在频域中通过线性动力计算方法进行导线的脉动风偏响应计算。该两阶段频域法与直接时域法相比计算效率大为提高,同时可保证计算精度。以特高压1000kV南荆I线为研究对象,构建四跨导线-绝缘子串有限元模型,考虑到连续多跨导线频率密集和模态复杂的特点,以能量法确定参与模态数,详细分析不同档距、挂点高差和运行张力条件下绝缘子串风偏角的变化规律,并分析规范中刚性直棒法的不足。结果表明,当线路杆塔存在高差时,呼高低的塔处于风偏的不利位置,更易发生风偏闪络事故;低呼高塔的绝缘子串风偏角会随着相邻塔呼高和线路运行张力的增大而增大,但随着相邻档档距的增加略有减小。相较于档距的变化,风偏角对挂点高差的变化更为敏感。     

某羊角型输电塔的风振响应分析

本文首先简述了应用线性滤波法中的自回归模型(AR模型)模拟出给定风速功率谱的风速时程序列,并验证其与目标谱的一致性,再通过规范公式推导脉动风载与风速之间的关系,从而得到作用在各节点的脉动风荷载时程样本。本文以某羊角形输电塔为原型进行了模拟计算分析,用有限元分析软件ANSYS建立了有限元模型,并用MATLAB生成塔架迎风面各节点上的风荷载时程信号作为动力输入。利用ANSYS对结构进行了模态分析,结果显示结构的基本模态为平面振动,但是同时具有扭转模态和局部振动模态;对此输电塔结构进行了平均风作用下的静力分析,同时,基于ANSYS时程分析方法计算了结构在一般风荷载作用下的风振响应。结果表明,在考虑一般风荷载作用的情况下,输电塔在顶部出现最大的位移和加速度响应,而在底部出现最大的轴力响应,但由于本文输电塔结构杆件的变截面设计,最大的应力出现在约1/3高处的杆件上。相对于平均风的作用,结构响应在一般风荷载下呈现出明显的动力放大效应。     

考虑潮位及动水压力影响的在役海上风电塔地震响应分析

为了准确评价潮间带海上在役风电塔结构在地震作用下的动力特性,以某1 000 MW近海及潮间带风电场的风电塔为研究对象,考虑潮位和动水压力影响,对其进行了地震响应分析。基于附加质量法建立了风电塔有限元模型, 对平均水深条件和极端高潮位条件下的风电塔结构进行了动力分析,并研究了冲刷效应影响下风电塔结构的自振特性。结果表明:仅考虑潮位变化引起的动水压力对结构的动力响应影响并不大,各项动力性能指标变化均在5%以内;冲刷导致的海床上覆土层的变化将影响到结构的自振周期,进而可能导致风电塔附加振动。     

抛物线拱桥在移动荷载作用下的动力响应分析

建立抛物线双铰拱桥的强迫振动的运动微分方程,分析了拱桥在移动荷载作用下的横向振动问题,将运动微分方程解耦,得到拱桥在移动荷载作用下振动时的动力响应并加以分析,通过实例计算,得到了拱桥在移动荷载不同行驶速度时的动力挠度曲线,并进行了比较分析。     

Wind-Induced vibration responses of prestressed double-layered spherical latticed shells

This paper focuses on the wind-induced vibration response of prestressed double-layered spherical latticed shell (PDSLS) structures by adopting time-domain analysis method. Welch spectrum analysis method is used to make precision evaluation of power spectrum of fluctuating wind speed time history simulated by weighted amplitude wavelet superposition (WAWS) method and linear filtering method of auto-regression (AR) model. Results show that the two methods produce little precision difference, but AR method is far more efficient than WAWS and is more suitable for wind speed simulation of PDSLSs. The effect of various parameters on the wind-induced vibration response of PDSLS structures are comprehensively investigated, including rise-span ratio, span, shell thickness, elastic constraint stiffness, prestress value, with or without cables and cable layout scheme. Results show that rise-span ratio and span are the major factors that affect wind-induced vibration response of PDSLSs. When cables are set, the wind vibration coefficient of nodal vertical displacement becomes smaller and more equally distributed, which demonstrates that PDSLSs are less sensitive to fluctuating wind effect than common latticed shell structures without cables. Finally, based on the envelopment concept and with the maximum dynamic and average wind-induced displacement responses as control indicators, the calculating method for global wind vibration coefficient (GWVC) of PDSLSs is proposed and the value with usual design parameters is given. Meanwhile, when the structure is made static analysis by means of the equivalent static wind load obtained from GWVC, the obtained internal member force response is relatively accordant with the actual response got from time-history analysis, and is a little safer.     

三维脉动风模拟技术在大跨机库风振分析中的应用

风荷载在大跨度屋盖结构设计中往往起主要作用,这使得该类结构的风荷载及风致动力响应研究日益受到关注与重视。结合大跨度机库屋盖表面脉动风作用特点,依据改进的Iwatani线性回归滤波器法并结合中心采样定理,实现了基于Matlab的超大跨度网架结构三维空间相关脉动风速时程模拟。以Davenport谱为目标谱对首都机场六机位机库网架所有上弦节点位置处的随机脉动风速时程进行了模拟。进而结合风洞试验数据,依据屋盖各节点风压系数将模拟的风速时程加载于机库结构并进行风振响应时域分析,以研究三维脉动风作用下超大跨度机库屋盖结构的响应特点。分析结果表明本文模拟空间随机脉动风的方法可以较好地考虑大跨机库表面的脉动风特点,为结构的风振时域分析提供准确的荷载时程。     

利用人工模拟脉动风压计算高层建筑横风向风振动力反应时程

根据日本规范中提出的横风向脉动风力谱系数函数,利用人工模拟横风向脉动风压时程的方法,提出了一个矩形平面高层建筑横风向风振反应时程的计算方法.在计算过程由横风向脉动风压谱系数公式模拟了建筑结构横风向脉动风压过程,采用N ewm ark法计算了两幢建筑物顶部的横风向风振反应.计算结果表明:在横风向脉动风压的作用下,结构的风振反应以共振响应为主,非共振响应仅为次要的部分,这与谱分析法得出的结论是一致的,从而说明了计算结果的正确性.这对于正确估算结构的风振反应值,为高层建筑风振控制措施设计提供参考依据具有一定的意义.     

考虑特征湍流影响的体育场悬挑屋盖脉动风压谱模型

基于风洞试验对体育场悬挑屋盖的脉动风压谱进行系统研究,旨在得到适用于此类结构的脉动风压谱模型,为风振响应分析提供必要的信息。通过对屋盖表面脉动风压进行谱分析,可知在屋盖前缘处的风压谱与来流风速谱较接近,但屋盖后缘处则差异很大,表现出明显的漩涡脱落特征。因此脉动风压自谱采用来流谱与漩涡脱落谱相结合的形式来描述,并通过权数因子体现屋盖表面不同位置处流场作用的特点。对于脉动风压互谱则用指数衰减函数来表示,并确定了适用于悬挑屋盖的衰减系数。为验证所提出风压谱模型的有效性及特征湍流对风致效应的影响,对系列悬挑屋盖结构进行风振响应分析,风荷载时程分别采用风洞试验测得的风压时程、基于建议风压谱模型模拟生成的风压时程、按拟定常假设生成的风压时程。基于建议模型得到的响应结果与试验结果基本一致,基于拟定常假设的风振响应极值偏小10%～15%,均方根值偏小30%～40%,脉动风压谱建模中不可忽略特征湍流的影响。     

Experimental and computational simulation for wind effects on the Zhoushan transmission towers

Long-span transmission tower and conductor line systems become important infrastructures in modern societies. The analysis of wind-induced dynamic responses of transmission towers is an essential task in the design of spatial lattice tower structures. Wind effects on the world's tallest transmission tower are presented in this paper. The tower with a total height of 370 metres, part of the Zhoushan long-span transmission project, enables high voltage conductor lines to span as long as 2750 metres over the typhoon-prone sea strait. A multi-DOF aeroelastic model test with and without conductor lines was carried out to investigate the dynamic performances of Zhoushan tower during typhoon events. Using the response measurement results in the wind tunnel, the inertial force based gust loading factors (GLFs) are applied to represent dynamic wind load effects on the tower for structural design purposes. Time domain computational simulation approach is also employed to predict dynamic responses of the transmission tower and the displacement based gust response factors (GRFs). The fair comparison of GLFs or GRFs are made between the results of the experimental approach and the computational simulation approach, which is an effective alternative way for quickly assessing dynamic wind load effects on high-rise and complex tower structures.     

矩形高层建筑结构扭转风振反应时程的分析计算

根据Davenport脉动风速谱函数与日本规范中提出的横风向脉动风力谱系数函数模拟的顺风向与横风向脉动风压时程,采用Newmark法计算了一栋高68m的高层建筑物的风振扭转动力反应时程。计算时考虑了顺风向脉动风压与横风向脉动风压的联合作用。计算结果表明:结构扭转振动加速度响应以共振响应为主,非共振响应仅占次要的部分,这与谱分析法得出的结论是一致的,从而说明了计算结果的正确性。这对于正确估算结构的扭转风振反应值,为高层建筑风振控制措施设计提供参考依据是有一定意义的。     

中空夹层钢管混凝土风力机塔架风振性能研究

传统风力发电机组塔架大多为锥形单管钢薄壁细长结构,此类结构在叶片转动及风荷载作用下易发生大的变形和振动。为克服传统风电塔自身发展的局限性并发挥中空夹层钢管混凝土(CFDST)结构优良的力学性能,基于某锥形钢塔筒,通过承载力等效提出CFDST塔筒结构形式,利用ABAQUS软件建立其风振性能有限元模型,对比了两种塔筒的振动模态。从时域和频域对二者在不同荷载工况下的动力响应特征进行对比分析,并对塔筒与叶片是否共振及瞬态冲击荷载下的振动进行了研究。结果表明:CFDST塔筒在保证原有钢塔筒抗弯承载力和刚度的同时,底部截面尺寸减小了25.6%,且不会与叶轮转动产生的谐波激励发生共振; 阻尼对风机塔筒位移、速度、加速度及应力响应幅值影响显著; 与钢塔筒相比,CFDST塔筒在正常运行荷载工况下峰值位移、加速度幅值和最大等效应力分别降低21.1%、30.2%和41.6%,而在暴风荷载工况下,分别减小14.4%、32.2%和36.3%; 研究成果可为相关塔筒的设计优化提供参考。     

钢管塔有限元模型快速建模及覆冰动力特性分析

采用通用有限元分析软件SAP 2000,选取1个500kV双回路直线型钢管输电塔架,通过建立空间桁架模型、空间刚架模型和由杆单元及梁单元组成的混合有限元模型,较全面分析讨论节点构造和节点刚度等因素对塔架动力特性的影响,系统研究不同有限元模型对模态分析结果的影响,指出各种有限元模型在塔架动力特性分析中的特点和适用范围。在模型分析的基础上,对不同覆冰厚度下的钢管塔动力特性进行分析,为进一步研究钢管输电塔在覆冰条件下的地震及脉动风动力分析提供基础。研究表明：塔架整体覆冰对钢管塔架的动力特性影响明显,钢管塔截止频率随覆冰厚度的增加而减小;塔架自振频率的减小幅度随覆冰厚度的增加而逐渐增大,因此在进行覆冰条件下的钢管塔动力分析有限元计算时,应特别重视覆冰对钢管塔架的动力特性影响。     

风荷载作用下钢塔架的疲劳寿命预估

结构的风致振动使得结构产生围绕平均应力的脉动应力 ,它能导致结构的疲劳累积损伤 ,可能造成结构在低于设计风荷载的各种水平风荷载往复作用下而失效。由于风荷载是钢塔架等钢结构的主要荷载 ,风荷载作用下上述结构的疲劳寿命预估因而是至关重要的。在作了一些简化假设后 ,得到了钢塔架疲劳寿命。由于塔架结构的顺风向响应为宽带过程 ,在考虑了窄带共振响应和宽带背景响应后 ,用等效窄带法得到了其疲劳寿命的计算公式。最后给出了一个疲劳寿命计算的工程实例。     

大跨度柱面网壳结构风荷载特性风洞试验研究

为研究大跨度柱面网壳结构受特征湍流影响的风荷载特性,在大气边界层风洞中对一大跨度柱面网壳干煤棚结构进行刚性模型同步测压试验,获得了结构表面测点在36个风向角下的测压数据。根据测试结果分析了结构的平均、脉动风压分布特性,脉动风荷载谱以及测点间脉动风荷载的相关性等。结果表明：结构在不同风向角下,特征湍流的影响情况不同,平均风压和脉动风压最大值出现的位置和范围存在较大差别;结构迎风位置测点脉动风荷载无量纲功率谱数值较大,且频谱成分复杂,随着气流向尾流区域发展,无量纲功率谱谱峰宽度及对应的无量纲频率具有增大的趋势,且高频段的衰减速度变缓;测点间脉动风荷载相关性随着频率及测点间空间距离的增加而减小,当频率达到30 Hz时,其相干函数值快速衰减,可以近似认为不相关。     

体育场悬挑屋盖空间风激动力响应和等效风荷载实用计算

本文推导了悬挑屋盖空间动力响应的理论公式,提出了等效静力风荷载实用计算方法。动力响应公式中考虑了空 间脉动风压分布和多个空间振型的贡献,且给出了显式表达式,工程应用方便;等效静力风荷载是基于惯性风荷载方法提 出的。结合等效风荷载的计算,本文利用两座体育场风洞试验的测压数据,拟合了其悬挑屋盖脉动风压谱的经验公式。经 工程算例表明,本文方法对悬挑屋盖的风振计算具有较理想的计算精度。