Theoretical And Experimental Study On Wind-induced Internal Pressure Response In A Building With Openings

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.