【作者】 徐海巍；

【导师】 楼文娟；

【作者基本信息】 浙江大学 ， 结构工程， 2014， 博士

【摘要】 建筑由于使用功能要求或者在强风作用下门窗破坏而形成开孔时,会使结构内部风压骤然增大。历年的风灾调查显示,多数房屋围护结构的破坏(例如屋盖掀翻和墙面倒塌)是由于内外压共同作用所造成的。当开孔大小符合某些条件时,内压将产生强烈的共振效应使得内压脉动得到大幅提高,对围护结构安全极为不利。我国经常受台风影响的沿海地区存在着大量低矮房屋和大跨厂房,合理的估算结构所受的极值风荷载有利于提高这些建筑的抗风性能,减少恶劣风环境下的经济损失。本文结合理论分析和试验对不同形式开孔结构风致内压的动力特性及其影响因素、关键的孔口参数取值、风洞试验方法等方面展开了系统的研究。本文从理论上推导了单一开孔、开孔双空腔、以及迎风面多开孔情况下内压的非线性传递方程,并分别对其进行线性化。结合模型试验验证了各传递方程的准确性,并分析了开孔面积,内部容积,风速风向等对脉动内压均方根、Helmholtz共振频率以及等效阻尼比等动力特性参数的影响。提出了随机荷载作用下未知惯性系数和损失系数的理论识别方法,并分别给出这两个参数的建议取值。自行研制了扬声器激振装置用于内压响应的研究,该装置能够产生频率和幅值可调节的简谐和随机外压。通过大量模型的扬声器激振试验和风洞试验来验证所推导识别公式的准确性,并对影响这两个孔口特征参数取值的因素(包括：结构柔性,模型安装方法,湍流强度,来流风速风向,开孔面积和位置,内部容积等)进行了深入地考察。基于相似性准则分析了风洞试验时各种开孔形式下为保证试验模型与原型内压动力特性相似性模型应该满足的条件,提出了准确测试内压的试验方法,并指出风洞试验过程中可能导致内压响应测试误差的情况。综合分析了开孔面积,开孔位置,建筑内部容积,来流风速和湍流度,以及内部干扰等因素对内压脉动,等效阻尼比以及共振响应的影响。比较了内外压脉动均方根之比的几种简化预测方法的适用性,分析了方程中待定常数的物理意义及其可能的影响因素。以4种开洞形式下某沿海地区大跨超高单层厂房的实际工程为例进行内外表压力的风洞测试,得出其风荷载及内压峰值因子的分布规律,并与规范体型系数和峰值因子的建议值进行了比较,重点考察了纵墙端部区的受力情况,给出了对屋盖和墙面受力最不利的风向角和开洞工况,为该类结构合理设计提供参考。采用CFD数值技术对不同长跨比相同单一开孔厂房纵墙的内外表面平均风压进行模拟并与风洞试验结果比较,验证了数值风洞的有效性。探讨了厂房长度对纵墙内外表面风压系数的影响,同时还研究了厂房端部效应区的范围以及厂房长度增长对其的影响。更多还原

【Abstract】 Dominant opening created in a building due to use function requirements or failure of windows and doors during sever wind events causes sharp increase of wind pressure inside the building. Over the years, investigation results of wind disaster show that actions of wind-induced internal pressure combined with external one contribute to the failure of most building envelope (such as roof overturn and wall collapse). When opening size satisefies certain conditions, fluctuating internal pressure is amplified by strong Helmholtz resonance which is quite disadvantage to building envelope safety. Given the growing number of low-rise buildings and large span factories in the typhoon-prone coastal cities of China, appropriate estimates of peak wind pressure on building envelopes are essential for improving wind resistance performance of those buildings and reducing property loss during severe wind condition. Both theoretical study and wind tunnel tests are adopted to systematically investigate the dynamic characteristics of internal pressure response and its influence factors for buildings opened in different forms. Critical orifice characteristic parameters and methods of wind tunnel experiments for opening structure models are also discussed in this paper.Theoretical nonlinear equations for describing internal pressure response to wind actions inside a building with windward wall dominant opening、multiple opening and internal partitions are derived and also are the corresponding linearization form of these equations. Experiments are carried out to testify the validity of the deduced equations and to investigate the effects of opening sizes, internal volume as well as wind velocity and azimuth on dynamic characteristic parameters such as root mean square internal pressure, Helmholtz resonance frequency, equavilent damping ratio,ect.Analytical methods for identifying ill-defined loss coefficient and inertial coefficient of opening models under excitation of random wind load are set up. And recommendation values for those two parameters are given respectively. To study internal pressure response, an exciter is developed based on a louder-speaker which can produce harmonic and random pressure with adjustable frequency and amplitude. In order to verify the accurancy of the proposed identification equations and understand factors influencing the two orifice characteristic parameters (including: structure flexibility, installation methods of wind tunnel models, turbulence intensity, wind velocity and azimuth, opening size and location, interal volume,etc.), both excitation experiments and wind tunnel tests are used to numerous models.Certain rules for wind tunnel tests of internal pressure are recommended based on similarity theory to make sure that the dynamic similarity of internal pressure response between full-scale and model-scale building is maintained. Incorrect wind tunnel method which may lead to deviation of measured internal pressure fluctuation from actual one are also presented. Effects of opening size and location, building internal volume, wind velocity and turbulence intensity in approaching flow, as well as internal interference on fluctuating internal pressure, equavilent damping ratio and resonance response are comprehensively explored. Applicability of different simplified equations for predicting root mean square ratio of internal to external pressure are analyzed. The physical meanings and possible influence factors of the uncertain parameters in these equations are explained.Wind tunnel experiments are applied to obtain internal and external pressure of a large-span high-rise single storey factory with4different opening forms. To provide reasonable reference basis for such factory design, distribution of internal and external wind pressure as well as peak factors of internal pressure on envelope are illustrated and compared with the code provisions. Special attentions are paid to the wind actions on both end of longitudinal walls. In addition, the most disadvantage wind azimuth and opening case for factory walls and roof are shown in this paper.Finally, CFD numerical technology is used to simulate both mean internal and external pressure on the longitudinal wall of factories with the same dominant opening but various aspect ratios. The reliability of the numerical simulation method is examined by comparing simulated results with wind tunnel test. The influence of factory length on mean internal and external pressure coefficients were studied. Moreover, the end effect range of longitudinal wall and its relationship with aspect ratio of a factory are discussed.更多还原