【作者】 杨有根；

【导师】 刘光栋； 李秋胜；

【作者基本信息】 湖南大学 ， 桥梁与隧道工程， 2007， 博士

【摘要】 本文主要对高层建筑结构在台风作用下进行现场实测分析,并对高层建筑风致作用进行数值计算,对于大跨度悬挑屋盖进行风洞试验和风致响应计算,并提出等效风荷载的实用计算方法。本文主要包括如下一些工作:(1)在对不同台风登陆后进行长时间连续观测获得的实测数据的基础上,系统地研究了台风的功率谱、湍流积分尺度和峰值因子等台风相关特征以及在台风作用下的被测结构的自振频率、加速度和阻尼特征等,包括湍流积分尺度、峰值因子自身特征及其和风速之间的相互关系、被测结构的自振频率及其在设计阶段通过有限元模型计算的自振频率之间的关系、被测结构的阻尼和振幅之间的关系以及实测结果和风洞试验结果的对比等,从而获得了较完整的风荷载和结构风致响应等相关信息,并对其成因进行系统分析研究,另外利用时域方法对高层建筑风致响应进行计算。通过这些系统而深入的研究,将为我国在台风作用下结构的动力学特征、风与结构的相互作用、风环境、风场模拟以及设计风荷载等方面的研究提供有价值的成果。(2)利用计算风工程的基本方法对高层建筑的风致作用进行数值评价,其中对计算风工程的计算原理和方法进行分析探讨,对其计算过程中运用不同湍流模型的优劣进行对比分析。在对钝体结构进行湍流计算时,本文提出相应的入口气流和边界条件的模拟方法;同时,对结构网格的划分,本文利用有限体原理和无网格原理相结合的原则提出实用方法,使其既能达到节约计算时间又能达到计算精度的要求。本文还利用不同湍流模型并编制相应的计算程序对高层建筑进行数值计算,并将其与风洞试验的测量结果进行对比,计算结果表明:对于常用几种湍流模型,利用动力亚格子模型的大涡模拟方法能较为准确地模拟出高层建筑在不同风向角下的阻力、升力和力矩系数。LES模型比RANS模型对阻力、升力系数和力矩系数具有较好的模拟结果,对于钝体周边的流场,一些典型的流动特征都能被准确地模拟出来。LES模型能较为准确的模拟出流场湍流,特别是这种模型能准确的捕捉到在转角处出现小的二次分离,而RANS模型不能准确的预测这一点。本文的研究结果将为数值计算在结构风工程中的应用提供重要的参考依据。(3)对大跨度悬挑屋盖在来流有干扰的情况下进行刚性模型风洞试验研究。在风洞试验中,利用技术措施对屋盖进行上下表面同步测压;并测量在不同的屋盖倾角、来流受到干扰以及不同的风向角情况下的屋盖风压分布特性。在对试验结果数据进行深入的处理和分析的基础上,获得了较完整的平均风荷载和脉动风荷载分布信息,包括平均风压系数和脉动风压系数随风向角的变化情况、平均风压系数和脉动风压系数在屋盖上下表面的空间分布情况、屋盖倾角的改变对平均风压系数和脉动风压系数产生的影响以及来流受到干扰情况下对平均风压系数和脉动风压系数产生的影响等,在此基础上系统研究了屋盖上下表面的平均风压系数和脉动风压系数的分布信息,并对其流场机理进行系统研究,从而为此类屋盖的设计和施工提供一定的参考依据。(4)研究大跨度悬挑屋盖的风振计算方法。本文运用随机振动力学和统计学相关知识并结合风对大跨度屋盖作用的相关特征,提出运用荷载相关法及协方差分析方法来对大跨度屋盖体系的各种响应进行求解:对平均响应利用结构力学知识进行求解,而对于脉动响应中的背景响应和共振响应则利用协方差分析方法和荷载相关法进行求解;最后对主次梁屋盖体系中的悬臂结构举例求解,并对求得的结果进行理论分析。(5)研究大跨度悬挑屋盖的等效风荷载的相关问题。本文通过对大量的试验数据的总结以及不同理论方法的比较,利用阵风荷载因子法提出有干扰和无干扰情况下的悬挑屋盖的等效静力风荷载的一般计算方法,从而避免在无干扰情况下,对屋盖的计算偏于不安全,而对于在有干扰情况下的计算又偏于保守,最后,将计算结果和不同求解方法的计算结果进行详细对比分析,发现本文方法能为解决工程实际问题提供一定的参考依据。更多还原

【Abstract】 This thesis mainly presented the field measurement analysis of tall buildings during passages of several typhoons; the numerical evaluation of tall buildings was conducted. The wind tunnel test on a rigid model of long span cantilever roof and the computational methods for wind-induced response of long span cantilever roofs were also studied. Finally, a simplified approach for estimating the Equivalent Static Wind Load of long-span cantilever roof was proposed in this study for engineering application purpose. The thesis was focused on the following aspects:( 1 ) This study presented selected field measurement results of wind characteristics and structural responses of super tall buildings, during passages of several typhoons. The field data such as wind speeds, wind directions and acceleration responses were simultaneously and continuously measured from the super tall buildings during typhoons. Detailed analysis of the field data was conducted to investigate the characteristics of typhoon-generated wind and wind-induced vibrations of these super tall buildings under typhoon conditions. The dynamic characteristics of the buildings were determined on the basis of the field measurements and comparisons with those calculated from the computational models of the buildings were made. Furthermore, the full scale measurements were compared with wind tunnel results to evaluate the accuracy of the model test results and adequacy of the techniques used in wind tunnel tests. The full scale measurements of wind effects on the instrumented tall buildings can provide a fundamental improvement of knowledge in structural dynamic characteristics, wind-structure interaction, wind climate, wind field modelling and design wind loads.(2) A comprehensive numerical study of wind effects on the Commonwealth Advisory Aeronautical Council (CAARC) standard tall building was presented. The techniques of Computational Fluid Dynamics (CFD), such as Large Eddy Simulation (LES), Reynolds Averaged Navier-Stokes Equations (RANS) Model etc., were adopted in this study to predict wind loads on and wind flows around the building. The main objective of this study is to explore an effective and reliable approach for evaluation of wind effects on tall buildings by CFD techniques. The computed results were compared with extensive experimental data which were obtained at wind tunnels. The reasons to cause the discrepancies of the numerical predictions and experimental results were identified and discussed. It was found through the comparison that the LES with a dynamic sub grid-scale (SGS) model can give satisfactory predictions for mean and dynamic wind loads on the tall building, while the RANS model with modifications can yield encouraging results in most cases and has advantage of providing rapid solutions. Furthermore, it was observed that typical features of the flow fields around such a surface-mounted bluff body standing in atmospheric boundary layers can be captured numerically. It was found that the velocity profile of approaching wind flow mainly influences the mean pressure coefficients on the building and the incident turbulence intensity profile has a significant effect on the fluctuating wind forces. Therefore, it is necessary to correctly simulate both the incident wind velocity profile and turbulence intensity profile in CFD computations to accurately predict wind effects on tall buildings. The recommended CFD techniques and associated numerical treatments provide an effective way for designers to assess wind effects on a tall building and the need for a detailed wind tunnel test.(3)The wind tunnel test on a rigid model of long span cantilever roof was conducted in this study. Experimental results demonstrated that the mean pressure for the surface taps at the front part of roof were uplift forces. The coefficients of mean wind pressure for these taps increased when the wind azimuth increased from 0 to 60 degree. Then it decreased when the wind azimuth increased from 60 to 90 degree. However, the coefficients of mean wind pressure at these taps remained almost zero when the wind azimuth increased from 90 to 180 degree. For the taps at the middle part of cantilever roof, the uplift forces were also presented. The coefficients of mean wind pressure also increased when the wind azimuth increased from 0 to 90 degree, and relatively smaller values were observed for the pressures at these taps compared to those for the taps at the front part of the roof. The similarity facts also exist for the pressure taps at the rear part of the roof. However, the relatively smaller values in the coefficient of mean wind pressure were found for the taps at the rear part when the wind azimuth changed from 90 to 180 degree. For the front taps of the cantilever roof, the coefficients of fluctuating wind pressure decreased with the increase of the wind azimuth. This mainly due to the less interference effect from the windward roof when the wind azimuth increased. However, the coefficients of fluctuating wind pressure for the middle taps didn’t vary with the wind azimuth. Meanwhile, the coefficients of fluctuating wind pressure for the rear taps normally increased with the increase of wind azimuth. The main reason would possibly be due to the fact that the rear taps were located in the area when the wind azimuth increased. Therefore, the intensity of turbulence would be magnified and the coefficient of fluctuating wind pressure would increase. Experimental results also showed that the coefficient of fluctuating wind pressure remained at the same value when the inclination of cantilever roof varied.(4) The computational methods for wind-induced response of long span cantilever roof were also studied in this study. The wind-induced responses include the mean wind-induced response and fluctuating response, while the latter response could be further divided into background and resonant component. As it is known, two types of structural systems are categorized for long-span cantilever roofs: main and sub-beam system and space truss system. The Load-Response-Correlation (LRC) method is adopted in this study to obtain the wind-induced response of long-span roofs. While the mean wind-induced response estimated by the common structural analysis method, the fluctuating wind-induced responses are obtained by the LRC method. By taking a long-span cantilever roof as an example, detailed study about its wind-induced response was conducted in this research work.( 5) Equivalent Static Wind Load (ESWL) for long-span roof was also investigated in this study. Several approaches to estimate the ESWL for long-span roofs, including gust wind load factor method, inertial wind load method, the method with the combination of background and resonant wind-induced component, the specific method proposed by Australia Wind Code, the time-history dynamic analysis method and LRC method, are studied comprehensively and compared with each other in this study. Finally, a simplified approach for estimating the ESWL of long-span cantilever roof was proposed in this study for engineering application purpose. The computational results obtained from this simplified method were compared with the results obtained from other mentioned approaches. It was found that that the proposed approach can be severed as a useful and effective tool for engineering application.更多还原