近海风机塔架风浪荷载及其响应分析

研究风暴潮环境下近海风机塔架所承受的风、浪、海流动力荷载的数值模拟与计算,探讨在这些动力荷载作用下风机塔架的位移及基底内力响应的变化规律。联合运用了快速傅立叶变换(FFT)方法和谐波叠加法进行脉动风的模拟,再由Morison方程计算浪和流荷载。算例分析表明,在风暴潮环境下,风机塔架的塔底水平力与倾覆力矩较大,通过调整角度降低叶片的迎风面积,可在一定程度上减小叶片上的风荷载,降低塔底最大主应力;在风荷载和浪流荷载的作用中,塔底弯矩主要由前者引起,而后者对塔底水平力的贡献较大。     

考虑流固耦合效应的海上单桩式风电塔动力响应研究

风荷载与波浪荷载是海上风电塔承受的主要荷载,对风电塔结构设计起着决定性作用,其动力响应极为复杂。以南通沿海3.0 MW风电机为研究对象,利用数值模拟和现场实测手段,考虑流固耦合效应,建立"基础-塔筒-机舱-风轮"整机模型、风荷载模型、波浪荷载模型,研究海上风电塔在风-波浪联合作用下的结构动力响应以及不同水深对风电机系统振动频率的影响。计算结果表明:采用考虑流固耦合效应与风电塔整机模型分析得到的计算结果与实测结果较一致,可为海上风电塔结构在风-波浪联合作用下的振动分析和结构设计等提供分析方法;波浪荷载对海上风电塔的动力响应存在一定的影响,以风荷载作为主要荷载计算的结果不甚合理;水深对结构低阶振动频率影响不大,但水深对风电塔系统高阶振动频率影响较大,水深越大,高阶振动频率降幅越大。     

水平循环荷载下高桩基础受力性状模型试验研究

近海高耸结构基础承受风,浪,波流等水平循环荷载作用,受力变形性状十分复杂.在饱和粉土地基中完成了单桩和群桩的水平循环加载试验,揭示了单桩和群桩响应随循环加载的变化规律.试验结果表明循环加载使桩周土体产生累积塑性变形,桩-土体系水平刚度随循环次数增加不断下降;先期循环加载对后期加载的刚度有着明显影响;群桩中各基桩分担的水平荷载比例随循环加载发生重分配,前排桩的作用得到更多发挥;荷载循环效应对群桩的影响大于单桩.基于p-y曲线法引入循环效应系数以考虑荷载循环的影响,并将该方法与其它文献方法和试验结果作了对比验证.     

随机车流下的风-汽车-桥梁系统空间耦合振动研究

在交通荷载观测及统计分析的基础上,获得交通状况的代表性数据,对记录的车型、车重、车距和车速进行统计,在此基础上进行随机车流模拟,编制随机车流模拟程序RTF(Random Traffic Flow),程序中首次全面引入车型、车重、车距和车速4个参数;建立可以考虑任意车辆数目、不同车道以及车辆相向行驶功能的随机车流下的风-汽车-桥梁系统空间耦合振动分析框架,编制相应的分析模块RTFWVB(Wind-Vehicle-Bridge system analvsis).以杭州湾跨海大桥为工程实例,详细研究密集、稀疏运营状态,车流单向、相向行驶以及侧风与车辆移动荷载对桥梁关键部位动力响应的影响.分析表明:密集运营状态下桥梁动力响应明显大于一般运营状态下的相应值;车流方向对桥梁振动影响不大;密集运营状态下车辆移动荷载主要决定桥梁动力响应的均值,而侧风主要影响桥梁动力响应的脉动部分,风速越大波动越显著.     

考虑脉动风影响的风电塔风致动力响应数值分析与现场监测比较

本文基于"风轮-机舱-塔体"三维仿真模型,进行风电塔在暴风荷载作用下的风致动力响应分析,并基于规范中的风荷载计算方法与动力分析方法对风电塔的应力、位移和内力进行计算分析,同时研究风电塔风轮受不利风向影响时的力学特性变化规律,并对风电塔在常规风荷载作用下的应力和位移进行现场监测比较研究。结果表明,基于规范计算的风电塔的应力、位移及内力要比动力分析的计算值偏小;脉动风时程激励下,风电塔的最大应力值低于结构的最小许用应力值,但结构顶部的水平位移超过结构的位移限值,在风电塔设计中应予以注意。风电塔受不利方向的暴风影响会产生很大的内力,塔底最大剪力和弯矩增大了91%和106%,在风电塔设计过程中应该重点考虑;基于常规风荷载作用下的应力和位移的数值仿真结果与监测结果吻合较好。     

输电塔-线体系完全气弹模型风洞试验研究

按照基本缩尺律,设计、制作出模拟输电塔-线体系的一塔两跨线完全气弹模型,并通过大气边界层风洞试验,测试了各种风速下输电塔在挂线和不挂线工况下的位移与加速度响应,观测了输电塔-线体系的极限风荷载和风毁模式,同时通过测量导地线线端应变和绝缘子应变,得到导地线传递给输电塔的静、动力风荷载。研究了塔线耦联对输电塔风振响应的影响,分析了单塔与输电塔-线体系气弹模型风振响应随风速的变化规律和频谱特点,得到了若干对输电塔抗风设计有参考价值的结论。     

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。     

能源群桩与单桩热-力学响应特性对比分析

针对热-力耦合作用下能源群桩和单桩连续72 h放热工况以及间歇运行工况的传热和力学响应过程进行了三维动态数值模拟,对比分析了二者连续运行工况下的桩身温度、桩身应力、附加温度荷载、桩身截面位移、桩侧阻力以及间歇运行工况下的出口水温、桩心温度和桩顶位移。结果表明：虽埋管出口水温相近,但群桩与单桩的桩身温度差异较大,进而会引起桩身截面位移以及桩身应力等一系列能源桩力学响应不同;对能源桩施加结构荷载和温度荷载后,单桩的桩身应力大于群桩中各桩的桩身应力,并在桩身中下部达到峰值,附加温度应力在桩身主体段几乎相等;桩基出现整体沉降,但随着加热的进行出现了桩顶向上移动、桩底向下伸长的趋势;侧摩阻力沿桩深方向不断增大,在桩底处达到最大值;间歇运行工况下,能源桩出口水温、桩心温度以及桩顶位移出现明显的波动,呈现出累加效应。     

双车交会过程的风-车-桥耦合振动研究

侧向风作用下,双车交会过程中车辆和桥梁的风荷载会发生突变。以大跨度悬索桥为工程背景,通过车桥组合节段模型风洞试验,测试不同状态车辆和桥梁各自的气动力系数。针对强风作用下双车交会过程,通过风-车-桥耦合振动分析,对比分析双车交会情况下车辆和桥梁的响应,讨论双车间距、风速、车速等因素的影响。研究表明双车交会时背风侧车辆风荷载突变使车辆的横向响应显著增大。     

风浪流荷载作用下导管架基础结构特性分析

在风、浪、流荷载作用下,海上风电导管架基础受到较大水平荷载,为保证结构的安全稳定,有必要考虑桩土相互作用的影响。依托阳江某海上风电项目,采用美国石油协会(API)规范中的P—Y曲线法模拟桩土相互作用,运用Stoke五阶波理论和API规范推荐的风荷载计算方法进行了荷载计算,基于ANSYS软件建立了导管架基础整体模型,并对风浪流荷载下结构的受力特性进行分析,判断结构强度、位移、变形是否满足要求,给出相应的计算过程和结论,为导管架基础设计提供理论依据和设计参考。     

高风载和高负荷

欧洲大件运输和移动式起重机协会（ESTA）和欧洲物流联盟（FEM）早在2010年4月就发出警告,提醒起重作业时风载考虑不当容易引发的危险,并发布了一系列内容详实、与风速有关的起重作业时起重机翻车事故的报道。     

山重水复有古村

在漳州与厦门两市接壤处的山重水复之中,有一座历史悠久,古风犹存的古村落。正因为这里山重水复、交通不便,没有受到现代文明过多的入侵,所以至今保留许多原生态的古风古貌。     

Influence of mean wind speed, surface roughness and structural damping on the reliability of wind loaded buildings

Recently it was shown that the parameters, such as mean wind velocity, variance of the turbulent wind motion and structural damping show a significant influence on the reliability of wind loaded buildings and, hence, the effect of these parameters is investigated in more detail in this paper. As a result of this analysis it is shown in quantitative terms how these parameters affect the respective estimates of failure probabilities. Computational models are suggested to consider the probability distributions of the mean wind velocity, the surface roughness parameter as well as the effect of nonlinear damping.     

Extreme wind speeds in mixed wind climates

In this paper, a technique is discussed which enables extreme wind speed probabilities in mixed wind climates to be determined. It is shown that in such wind climates the method is likely to yield more accurate probability estimates than the traditional Gumbel analysis of annual wind speed maxima, particularly for annual probabilities of less than 2% (i.e. return periods greater than 50 years). The technique requires a separate analysis of each significant wind-producing meteorological phenomenon and practical methods of achieving this are presented. Extreme wind speed parameters obtained from each analysis may then be combined to yield a “composite extreme wind speed diagram” and several examples illustrating this procedure are shown. By means of a numerical simulation of a typical mixed wind climate, a detailed study is made of the distribution of extreme wind gusts from different meteorological phenomena. This study indicates that a Gumbel analysis of 20 annual maxima may severely underestimate low annual probability (i.e. long return period) gust speeds.     

Compensation of high-frequency components of wind load by wind tunnel testing

To analyze the wind-induced response of structures, wind tunnel tests are often carried out to determine the wind loads on structures. However, due to the influence of similarity requirements in wind tunnel tests, the resulting data from the model test still needs to be translated by similarity rules for predicting the real loads on prototype structures. During this process, an inevitable result is that the high-frequency components of fluctuating wind loads get lost, which leads to some unexpected errors in the subsequent wind-induced response analysis. To solve this problem, a frequency compensation method is put forward. The purpose of this method is to reconstruct the high-frequency part of fluctuating wind loads based on experimental data and some basic principles of the aerodynamics of bluff bodies. The causes and effects of the frequency compensation problem are discussed first, then a practical method of frequency compensation is proposed by combining the fluctuating wind energy spectrum theory and the Proper Orthogonal Decomposition technique. Based on this method, the wind-induced response of a single-layer reticulated shell is analyzed to show the validity and necessity of this method.     

Small wind turbine power control in intermittent wind gusts

This paper analyzes control strategies for a small scale wind turbine in intermittent winds using a computer model based on wind data collected on-site and computer simulation data. Standard generator control with a lowered gain was found to produce the greatest power capture by biasing the rotational speed towards high energy wind gusts. Optimal gain was able to be determined by calculating an estimated wind speed using physical and measured quantities. An augmentation to the standard control provides a method for capturing power safely beyond the rated wind speed.     

Specification of the design wind load based on wind tunnel experiments

Once a high-quality wind tunnel experiment with no major flaws on the experimental side has been performed and the data have been processed/translated appropriately to the design-decisive variable, the final step is to estimate the appropriate load or load effect coefficient for the specification of the design wind load. Four questions arise: what is the appropriate length of a single run in the wind tunnel, what is the appropriate fractile of the observed extreme coefficients, how many independent experiments are required to estimate this fractile and what should be the target confidence interval. The paper tries to give some answers to these questions and discusses the findings in regard to some wind load codes.     

广州塔风荷载及风洞试验研究

广州塔总高600m,塔体外形复杂,基本周期长,对风荷载的响应比较敏感,风荷载成为结构设计的主要控制荷载。针对广州塔的特点,分两阶段进行了风工程研究,第一阶段解决外界风的输入问题,第二阶段解决结构在风荷载作用下的响应问题。风荷载及风洞试验的主要成果可作为类似工程结构设计的参考资料。     

Measurements of wind drag on people standing in a wind tunnel

This report describes an experiment in which measurements were made of the wind drag on 331 people standing in turn in a wind tunnel. The results were analysed in terms of projected areas and drag coefficients, as is customary with wind tunnel measurements. Areas were then expressed as ratios to a person's total body surface area, calculated from weight and height. It was found that these area ratios and the drag coefficients could be related to the type of clothing, and eight categories were selected. The results thus provide a simple way of estimating the wind drag on a person for a known windspeed if his weight, height and type of cloting are known.     

北京当代MOMA风载及风环境数值模拟研究

根据计算流体动力学(CFD)的基本原理,基于计算流体力学软件Fluent平台,对当代MOMA工程的建筑群进行数值风洞模拟.获得12个不同风向下建筑物表面风压分布参数和建筑群区域不同高度的风环境参数.结果表明,建筑群的互相干扰既会影响建筑物表面的风压分布,又对不同区域的风向和风速有重要影响.来流上游建筑物的阻挡,会造成下游建筑物迎风表面压力值的减少,局部的风速加剧又会加大周围建筑物表面压力值;在产生流动分离和涡脱落的区域风速较高,而背风区域的风向与来流风向有较大差异.数值模拟获得的结果为建筑群的优化设计提供了重要参考.