汉江大跨越塔风荷载模拟

风荷载是各种工程结构的重要设计荷载,对于输电塔等高耸结构常常起着主要的作用。因此准确、真实地模拟大型跨越塔的风荷载,对于研究其动力特性、风振响应具有十分重要的意义。     

浅析高层建筑的横风效应

高层建筑的横风向荷载及响应问题非常复杂,来流紊流、尾流和气动反馈的激励与其息息相关,风荷载是高层建筑所承受的主要侧向荷载之一。在沿海地带和非地震区,风荷载又常常成为结构设计的控制荷载,而高层建筑结构设计中的重要部分是包括内力、风荷载、位移、加速度等结构抗风分析。目前,高层建筑横风向风效应研究的内容主要包括以下三个方面:确定横风向气动力、识别横风向气动的阻尼和计算横风向等效静力风荷载的方法,同时确定高层建筑横风向风效应的主要手段有风洞试验、数据拟合和参数识别技术。本文主要讲了横风向气动力的确定、横风向气动阻尼的识别以及横风向等效静力风荷载的计算方法三个方面的内容。     

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。     

高层建筑等效静态风荷载的确定

风荷载是强风区高层建筑的主要侧向控制荷载,确定脉动风荷载是高层建筑结构设计的需要。借助于高频动态天平试验和风压测量试验,分析讨论了沿建筑物高度分布的平均风力、脉动风力、风致振动惯性力以及建筑结构设计所需要的等效静态风荷载的确定问题,可为高层建筑结构设计中的风荷载确定提供参考。     

北大体育馆屋盖结构风荷载分布特性的试验研究

风荷载是控制大跨度钢屋盖结构设计的主要荷载之一。结合北京大学体育馆屋盖结构的风洞模拟试验,以屋盖上的平均风荷载和脉动风荷载为研究对象,对屋盖上的风荷载分布特性进行了详尽的分析。结果认为:整个屋盖所受风荷载主要以负压为主,屋盖悬挑部分在迎风时产生“上吸下顶”的叠加作用,其他风向为“上吸下吸”的抵消作用;屋盖角部的风荷载一般也很大,在结构设计时应采取必要的构造措施;脉动风荷载对于总的设计风荷载来说不能忽略,准定常理论不适合用来计算大跨度屋盖的风振响应。     

大跨度结构在风荷载下的动力响应

风荷载是大跨度结构设计中的主要控制荷载之一。通过对大跨度车站屋盖进行有限元建模,基于自回归法,编制MATLAB计算程序,模拟车站屋盖典型节点风速时程曲线,将模拟风速时程转化为风荷载时程,采用瞬态分析法得出屋盖的动力响应,以供类似工程参考借鉴。     

基于高频天平测力试验的广播电视塔等效静力风荷载研究

基于高频天平测力试验理论,基于电视塔力学模型分析了风致结构响应及等效静力风荷载的计算方法。本文重点讨论了平均风荷载分布形式问题和外侧网架结构与内侧筒体结构的风荷载分配问题,说明采用一阶振型假定计算的平均风荷载分布与实际分布之间存在差异,采用指数分布形式的体型系数可解决这一问题。以六安电视塔风洞试验项目为例分析了采用振型分布形式风荷载与基于体型系数指数分布的风荷载的差异。     

风洞试验在我国建筑工程中的应用简介

对高层建筑、大跨空间结构、高耸塔桅结构等建筑物和构筑物而言，风荷载是结构设计的控制荷载之一。同时，随着建筑群的涌现，风环境也越来越受到工程界的关注。当前，风洞试验是研究风工程的主要手段。本文简要介绍了风洞试验，回顾了近年来风洞试验在我国建筑工程中应用的基本情况。     

广州西塔风荷载研究

广州西塔是广州双塔的西塔楼,目前为华南地区第一高楼,高宽比超过6.5,主塔楼结构采用钢管混凝土斜交网格外筒+钢筋混凝土内筒的筒中筒体系。由于广州为台风多发地区,风荷载为其结构设计的控制荷载,故对其抗风设计进行了详尽的介绍。通过风气候分析确定了区域风况和设计风参数,以及与风响应有关的结构参数,并通过模型风洞试验确定了大楼的等效风荷载取值,并对大楼舒适度进行了判别。     

高耸结构设计规范风荷载研究进展及修订建议

风荷载是高耸结构的主要设计荷载，由于我国建设的迅速发展，原来的部分条文已不能适应当前实际工程的需要。基于研究的不断进展、荷载规范的修订变化和国外相关规范的接轨适应，高耸结构设计规范风荷载条文的修订已迫在眉睫。本文对主要部分：基本风压、地貌、风压高度变化系数和横风向共振响应作了详细的研究和分析。     

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.     

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.     

Parametric wind design

Although gradual, the changes in the weather patterns are also noticeable and impactful to architectural design. If the local microclimate is taken into account early in the conceptual stage of design, the longevity of the ultimate structure can be greatly enhanced, despite challenging environmental factors. Parametric designing enables to discover the optimal architectural shape based on specific weather data. The paper intends to investigate how this design approach, coupled with Computational Fluid Dynamics simulations, can be used to create a wind-induced architecture. Both the benefits and the limitations of this approach are explored in detail. The interaction between an architectural shape and wind flow is tested in a study called ‘FlowBrane’. The process of (1) designing a parametrically changeable geometry, (2) testing its behavior in the wind, and (3) evaluating the results allows looping back to the initial geometric design, continuing to improve the design and ultimately the performance of the architecture in the specific wind conditions of the chosen site. However, the need to test multiple geometries separately and to adjust the wind simulation for each test (and for every wind direction) remains a disadvantage that should be addressed in further research.     

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.     

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.     

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.     

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.     

Reliability analysis of wind turbines under non‐Gaussian wind load

Based on translation models, both Gaussian and non‐Gaussian wind fields are generated using the harmony superposition method for examining the reliability of a typical wind turbine at operational and parked conditions. Using the blade aerodynamic model and multibody dynamics, wind turbine responses are calculated and then probability characteristics are analyzed in details. The short‐term extreme response distribution is estimated by the average conditional exceedance rate method at each mean wind speed bin, and the long‐term extreme response distribution is then determined by further integrating the short‐term extreme response distribution conditional on wind speed with the distribution of mean wind speed. Additionally, crack initiation life and crack propagation life are evaluated using the linear cumulative damage theory and linear crack propagation theory, respectively. The results indicate that non‐Gaussian characteristics of wind inflows have a noticeably greater influence on both extreme response and fatigue damage, and the Gaussian assumption cannot suit wind turbine in complex terrain.     

A study of wind and buoyancy driven flows through commercial wind towers

Commercial wind towers have been the focus of intensive research in terms of their design and performance. There are two main forces which drive the flow through these devices, external wind and buoyancy due to temperature difference. This study examines the relationship between these two forces and the indoor ventilation rate achieved. The work uses computational fluid dynamics (CFD) modeling to isolate and investigate the two forces and draw comparisons. The study found that as expected the external driving wind is the primary driving force providing 76% more internal ventilation than buoyancy driven flow, which is deemed secondary. Moreover the study found that the effect of buoyancy is insignificant without an external airflow passage other than the wind tower itself. The addition of an external airflow passage such as a window in combination with buoyancy force increased the indoor ventilation by 47%. Therefore the careful positioning of windows in conjunction with internal heat source has the potential to overcome the lack of external wind driven forces in dense urban environments.     

数值风洞在大跨屋盖结构风荷载确定中的应用

运用计算流体力学数值模拟技术对大跨屋盖结构表面风荷载进行了研究。对平屋面和曲面屋面表面风压分布进行了数值模拟。在此基础上,对大庆石油学院体育馆屋盖表面进行了风洞试验和数值模拟的对比研究,并对大射电望远镜FAST反射面的风压分布及其周围流场进行了数值模拟,为该工程的结构抗风设计提供了参考。