任意排列两方形断面高层建筑风致干扰机理研究

风致干扰效应是高层建筑群抗风设计中的常见难点问题之一。采用刚性模型测压试验,研究了均匀层流和两种大气边界层风场条件下任意排列两方形断面高层建筑的风致干扰效应,通过平均和脉动基底弯矩系数的干扰因子、风力系数、风压系数分布以及风荷载功率谱的研究,解释了其风致干扰效应的机理。结果表明,任意排列的两方形断面高层建筑风致干扰中,至少存在横风向静力干扰、顺风向静力干扰和横风向动力干扰三个值得注意的干扰区域。 窄道形成的加速效应使受扰结构上形成指向施扰建筑横风向平均吸力和阻塞形成的受扰建筑的横风向平均推力;遮挡效应使得受扰建筑承受指向位于上游的施扰建筑的顺风向风力;漩涡叠加增强位于尾流区受扰建筑上的横风向脉动荷载。不同风场的试验结果表明,提高来流的紊流度有助于减弱上述干扰效应。     

高层建筑顺风向脉动荷载相干性研究

在确定高层建筑顺风向风致响应及等效静力风荷载时,顺风向荷载的竖向相干函数是非常重要的因素之一。目前的大多数研究均是以风速的相干函数来代替风压的相干函数,导致计算结果的误差较大。根据多个高层建筑模型表面测压风洞试验结果,详细分析高层建筑脉动阻力在B、D两类风场中的竖向相干特性,给出顺风向阻力竖向相干函数衰减指数CDz的公式,并与有关文献中提出的Davenport、Shiotani、ECCS等三种风速相干函数的表达公式进行比较,指出阻力相干性要明显大于风速相干性。结合准定常理论,计算一栋实际高层建筑的顺风向风致响应。结果表明:利用给出的阻力竖向相干函数得到的结果与根据风洞试验数据计算的结果相吻合,而其他几种表达公式导致的响应误差则较大,最大可达30%。     

Correction of direction reduction factors of extreme wind speed considering the Ekman spiral in the wind load estimation of super high-rise buildings with heights of 400–800 m

The wind direction in the atmospheric boundary layer (ABL) twists with height due to the Coriolis force; this phenomenon is called the Ekman spiral. However, this phenomenon is generally not considered in the present wind load estimation of super high-rise buildings, which may lead to an incorrect estimation and affect the safety of structures. Therefore, this study considers and analyzes the influence of the Ekman spiral phenomenon in the wind direction reduction effect (WDRE) of the wind load of super high-rise buildings. First, this paper proposes an empirical fitting equation for the twisted wind direction angle for a height of 100–800 m according to the classical Ekman spiral theory model (CE model). Subsequently, on the basis of twisted wind, this paper proposes a method for the correction of the wind direction reduction factors (WDRFs) of strong winds considering the influence of the Ekman spiral phenomenon in the design wind load estimation of super high-rise buildings with heights of 400–800 m. A high-frequency balance force measurement test of a square-section super high-rise building model was performed to analyze the influence of the Ekman spiral phenomenon on the WDRE of the aerodynamic force and wind-induced response. Three Chinese cities (i.e., Beijing, Wuhan, and Kunming) are selected as case studies to illustrate the importance and necessity of the correction method. The results demonstrate that the proposed empirical fitting equation accurately determines the twisted wind direction angle at different latitudes and altitudes. Furthermore, estimating the design wind load while considering the WDRE and neglecting the influence of the Ekman spiral phenomenon may lead to a significant underestimation of the wind load of super high-rise buildings, rendering the designed building structure more dangerous.     

Characteristics of pressure distribution and solution to the problems caused by stack effect in high-rise residential buildings

This paper shows the characteristics of pressure distribution caused by stack effect in high-rise residential buildings and proposes solutions for stack effect problems during the cold season. First, field measurements were conducted in two high-rise residential buildings in Korea to understand the characteristics of pressure difference and problems due to stack effect. Next, several high-rise residential buildings were simulated to confirm these characteristics and problems. From the field measurements and simulation results, the Thermal Draft Coefficients varied from 0.20 to 0.49. These values meant that most of the stack pressure difference in high-rise residential buildings acted on interior partitions rather than on exterior walls, so that serious problems due to large pressure differentials can occur on the inside of the building. The separation method which includes installing ‘air-lock doors’ between the elevator core area and residential area, is proposed to solve the pressure difference problems.     

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。     

A Comparative Study on the Influence of Ventilation on Weather- and Fire-Induced Stack Effect in the Elevator Shafts of a High-Rise Building

This work assessed the impact of ventilation on both weather- and fire-induced stack effect in an 18-story high-rise office building. Elevator shafts are considered the main route of vertical air movement. Pressure distribution induced by cold weather within the elevator shafts was calculated theoretically. Computational fluid dynamics simulations of fire in the same high-rise building under different ventilation conditions were carried out with a fire dynamics simulator. It was found that ventilation exerted a more complex impact on fire than the weather-induced stack effect. For the weather-induced stack effect, the ventilation condition of the building only affected the height of the neutral pressure plane; in fire situations, it did not only affect the height of the neutral pressure plane in a similar manner to the weather-induced stack effect, but also influenced temperature and pressure distributions in the elevator shafts. The smoke movement and the distributions of temperature and pressure in elevator shafts are also learned. The smoke movement in high rises experienced four typical stages after ignition. The ventilation condition of the fire floor influences gas flow into elevator shafts, while that of the upper floors impacts the smoke rise speed in vertical shafts. When the stack effect finally reaches steady state, the gas temperature in the shaft decreases exponentially with height. Based on this assumption, a theoretical model was presented to characterize the fire-induced stack effect in typical high rises. Results showed that the model successfully predicts the pressure distribution in high-rise buildings.     

厦门市高层建筑群风场的数值风洞模拟分析

针对高层建筑群的风压、风荷载的分布问题,应用数值风洞方法模拟厦门市高层建筑密集区的风场,并根据数值模拟结果分析高层建筑群静力风效应的一些基本特点。分析结果表明:风场上游的高层建筑对下游的建筑有一定的遮掩效应;当建筑物之间间距较小时,容易产生狭缝效应;在建筑群的外围,迎风面平均风压力较大。同时根据上述分析结果,提出了一些具体的设计建议。     

Effect of aspect ratio on the aerodynamic performance and correlation of square section building exposed to twisted wind profile

This study investigates the aerodynamic performance of three square-section buildings with different aspect ratio (AR = 1:1, 1:4, and 1:6) exposed to twisted wind profile (TWP) by pressure measurement test. The effect of AR on the correlation of wind loads specifically for TWP is systematically revealed from both time–frequency domain and local–global perspective. Results show that compared with its counterparts in conventional wind profile (CWP), the effect of AR on aerodynamic load under TWP becomes significantly different and more prominent, which can be categorized into two types of patterns. For pattern low-rise building, TWP is more resembling the condition of CWP with certain attack angle. For pattern high-rise building, TWP results in stronger momentum exchange along building height but suppresses fluctuating feature associated with Karman vortex. As a result, under TWP, mean base moments of all buildings are enhanced except for longitudinal component of case AR = 1:4 and 1:6; while the fluctuating base moment for three AR cases is all reduced, which indicates that dynamic pattern of wake flow is suppressed. Moreover, the discrepancy of local wind load between case CWP and TWP concentrates on the lower-middle location for high-rise building but distributed evenly along all low-rise building height. Additionally, it is found that the effect of AR on aerodynamic correlation exhibits different mechanisms and patterns when building is under the impact of CWP or TWP.     

高层建筑表面风压系数分布公式的数值计算与拟合

高层建筑物结构风荷载与暖通渗风量的计算都依赖于建筑物外表面上的风压分布资料与风压系数的具体数据。对不同风速作用下不同体型和尺寸的空气绕流高层建筑模型外表面上的风压进行了数值计算，利用计算结果对风压系数分布进行了数学回归，并拟合出风压系数分布公式。     

Distribution of background equivalent static wind load on high-rise buildings

In this paper, the along-wind and cross-wind fluctuating load distributions along the height of high-rise buildings and their correlations are obtained through simultaneous pressure measurements in a wind tunnel. Some typical methods proposed in some relative literatures, i.e., load-response correlation (LRC), and quasi-mean load (QML) and gust load envelope (GLE) methods, are verified in terms of their accuracy in describing the background equivalent static wind load distribution on high-rise buildings. Based on the results, formulae of the distribution of background equivalent static load on high-rise buildings with typical shapes are put forward. It is shown that these formulae are of high accuracy and practical use.     

周边高层建筑对大跨度曲面屋盖的气动干扰

结合无锡新区科技交流中心的风洞试验,分析了有无周边建筑两种情况下的风压分布,并对梅花形屋盖的花蕊、花瓣凹弧面和花瓣凸弧面3个典型部位的风荷载体型系数进行了研究,获得周边高层建筑对大跨度曲面屋盖气动干扰的相关结论:虽然受扰建筑的最不利风向角和风压发生很大变化,但是最危险部位始终处于檐口附近,而且是负风压为主;在"兜风效应"的作用下,受扰建筑的风压会急剧增大;在"阻挡效应"的作用下,受扰建筑的风压存在由负压向正压变化的趋势;屋盖凹弧面的槽向与风向角一致时,存在涡流作用与"兜风效应"叠加的现象,受"吸"破坏力极大,在曲面屋盖设计中应予以重视。     

基于风洞试验的对称截面高层建筑三维等效静力风荷载研究

基于刚性模型表面测压风洞试验建立高层建筑三维风荷载模型,进而运用振型加速度法求解风振响应动力方程,得到了包含拟静力项和惯性力项的弹性力响应解,并推导了对称截面高层建筑顺风向、横风向和扭转向风致随机内力响应。在此基础上提出了基于内力响应等效的可考虑高阶振型贡献的对称截面高层建筑顺风向、横风向和扭转向等效静力风荷载计算方法。结合某一对称截面高层建筑工程实例,对采用上述方法计算得到的结构三维等效静力风荷载进行分析并与我国规范方法顺风向等效静力风荷载计算结果进行比较。结果表明,高层建筑结构抗风设计应该考虑三维等效静力风荷载,且二阶振型对高层建筑等效静力风荷载的贡献不可忽视。     

基于极值相关性的超高层建筑风荷载组合研究

为研究不同长宽比超高层建筑三维风荷载组合,通过高频测力天平风洞试验得到了5种长宽比的矩形超高层建筑基底剪力、弯矩和扭矩时程。基于试验数据和计算结果,分析了三维风荷载效应的分布及其极值相关性。在此基础上,对比分析了不同长宽比的超高层建筑顺风向与横风向、顺风向与扭转向以及横风向与扭转向之间的风荷载效应极值分布规律和统计参数。最后,采用概率统计方法评估了不同长宽比对结构三维风荷载组合系数的影响,并给出了一组基于极值相关性分析的结构三维风荷载组合系数推荐值。结果表明：对于超高层建筑,虽然不同方向风荷载效应之间相关系数可能很低,但其三维风荷载效应极值相关性不可忽略;以横风向或扭转向为主方向进行组合时,其余方向同步比值存在明显的非高斯分布特性;对于不同长宽比超高层建筑,其极值相关性的差异会导致组合系数存在差别,在确定风荷载组合方法时,应考虑长宽比的影响。     

风洞实验及其在建筑领域应用的研究

近年来,由于建筑工程材料及施工方法的大幅进步,风力成为超高层建筑、体育场馆大跨屋盖、斜拉桥等结构的主要水平荷载。同时随着城市高层及高密度建筑的不断出现,城市空间构成变得非常复杂,由此而产生的各种风环境问题日益受到人们的注意,因此对建筑风环境进行研究很有必要。本文通过探讨风洞实验及其在建筑领域的应用,研究风洞实验在应用于建筑领域的进一步发展中,要注重改进修正的要素及其重要性。     

外凸式矩形高层建筑风压研究

针对外凸式矩形高层建筑结构外形复杂且其风荷载值无法通过建筑荷载规范直接获得的情况,以丝绸之路世界贸易中心外凸式矩形高层建筑为研究对象,通过风洞试验获得其风荷载值,并与规范给出的矩形结构体型系数进行对比,总结外凸式矩形建筑结构风荷载规律。基于Fluent软件,选用不同湍流模型,对外凸式矩形高层建筑进行数值模拟,并将计算结果与风洞试验结果进行比较,验证数值模拟方法的可行性。结果表明:该高层建筑迎风面的体型系数与规范接近; 背风面底部区域的体型系数比规范值大约70%,其他区域与规范值接近; 侧面体型系数均大于规范值,且最大负压出现在侧面; 对于外凸式矩形高层建筑结构,外凸结构风压较相邻区域增大,凹进结构的风压较相邻区域减小; 体型系数沿高度方向变化较大,凸出结构为迎风面时,其下方相邻区域体型系数比规范值小近50%; 数值计算结果与试验数据整体趋势基本一致; Realizable k-ε模型的数值模拟结果要优于Standard k-ε模型; 对于矩形高层建筑,凸出结构为迎风面时,其相邻上部区域和背风面下部区域风荷载不仅受凸出结构的影响,而且还受到凸出结构宽度的影响,其对体型系数的影响幅度为±20%之间。     

拟建高层建筑风环境对周边建筑遗产影响评估——以广州同盛机器厂旧址为例

高层建设项目将对风环境造成严重影响,给遗产保护利用带来新的问题与隐患。于是在城市规划设计早期,评 估拟建高层建筑风环境对周边建筑遗产的影响显得尤为重要。以规划中的广州白鹅潭国际中心商贸区及其中文物建筑 群——同盛机器厂旧址为例,应用 CFD 软件 Phoenics 模拟典型工况下拟建高层建筑风环境的影响。结果显示：①强台 风工况下,屋面风荷载未超过安全限值,由风压分布得出易受破坏部位;②“回南天”工况下,区域通风效果较好,但 风影区影响较大,存在加重生物侵害的隐患;③夏冬季工况下,风廊改善夏季风环境的作用明显,冬季在高层建筑附近 出现下行的高速冷风。依据建筑遗产受影响情况作出预评估,可指导城市高层建筑建设与周边建筑遗产保护协同进行。     

高层建筑水平悬挑遮阳板风荷载的风洞试验研究

高层建筑悬挑遮阳板等小尺寸构件直接承受风荷载作用,在强风作用下的安全性备受关注。相对于建筑的整体尺寸,悬挑遮阳板很小,难以在缩尺模型上直接模拟,因此在实际工程的风洞试验研究中常常被简化或者忽略。研究中利用3D打印技术制作了精细化的有悬挑遮阳板的高层建筑风洞试验模型,并在打印遮阳板模型时直接预留测压管道,分析了水平悬挑遮阳板的风压分布规律及遮阳板对建筑立面风压的影响,并对基于建筑立面风压的悬挑遮阳板风压估计方法的估算误差进行了评估。研究结果表明：高层建筑水平悬挑遮阳板的最不利净风压的最大值出现在顶层遮阳板处;水平悬挑遮阳板的存在能较大程度地削弱建筑立面上的最不利负风压;悬挑遮阳板最不利风压可利用其上下两侧附近建筑立面测点的风压差近似估计,但对于建筑立面边缘附近的悬挑遮阳板端部以及建筑底部附近的最底层悬挑遮阳板上的最不利风压,这种方法的估算误差较大。     

A study on the development and application of the E/V shaft cooling system to reduce stack effect in high-rise buildings

This study suggests the E/V(Elevator) shaft cooling system as a new approach to reduce the stack effect and the related problems in high-rise buildings. The basic characteristics on its application were analyzed with some simulations in this study. Moreover, the system was applied to an actual building and its performance was evaluated through the measurements.The system can reduce the stack effect itself and the related problems simultaneously and it can reduce the pressure and the air flow rate in each part of a building in the same ratio. These features were shown in the results of the simulations; for the examples, when all the E/V shafts were cooled from 22 °C to 12 °C, the stack effect and the pressure in each part of the modeled building were decreased by about 27%.In the field measurements, the wind velocity through the E/V door was decreased effectively in the whole building; its reduction ratio at the lobby floor was about 25% and at the upper floors (37F, 38F) about 10% respectively. But, the neutral pressure level at the E/V shaft was moved by the vertical temperature difference in the E/V shaft because of the inflow ducts concentrated in the lower part of the E/V shaft. This movement was also shown in another simulation on the same conditions as the measured ones. It is very important to minimize the vertical temperature difference in the E/V shaft to maximize the reduction effects on the problems.     

大高宽比方形截面高层建筑的横风向风荷载及风致响应研究

基于一栋高层建筑的刚性模型表面压力测量风洞试验数据,分析了高宽比较大且截面为方形的高层建筑横风向风效应的共同特征。得到如下结论:高层建筑横截面为方形时,其横风向风荷载主要由规则性旋涡脱落导致的尾流激励构成,为窄带随机激励;当高层建筑的高宽比较大时,基阶固有频率相对较低;当高层建筑兼具方形截面和大高宽比这两个特征时,其基阶固有频率可能接近其尾流的旋涡脱落频率,从而发生剧烈的横风向涡激共振。建筑结构截面的小幅增大可使这种剧烈的横风向涡激共振得到有效控制。上部外形的适当处理,也可能有效降低高层建筑的横风向等效风荷载。低矮群楼的出现将在一定程度上影响高层建筑的风荷载。     

高层建筑室外风速简化计算方法研究

由于地表摩擦的结果,使接近地表的风速随着离地面高度的减小而降低,而大部分建筑物都在这个范围内。因此,室外风速对高层建筑热负荷的计算有重要意义。但是室外风速随高度变化呈对数曲线状,因此,不适合直接应用于高层建筑板壁传热量计算。通过根据不同层高进行分段直线拟合来代替曲线和计算出风速均值,从而达到简化的目的。