Wind-Induced Internal Pressure Of Structure With Openings And Its Coupling Effect With Flexible Roof

Investigation of windstorm disaster indicates that wind-induced damage of low-rise buildings and long-span flexible roof structures are generated by combined actions of internal and external pressures. Increment of internal pressure caused by partial openings or sudden opening is a serve threat to security of the buildings. However, the research about mechanism of generating internal pressure and how to consider internal pressure in structure design are still in exploratory stage. Thus the problem of the internal pressure is a newly developing subject in modern wind engineering and profound investigation of the internal pressure and the wind-induced internal pressure of structures with openings and its coupling effect with flexible roofs have vital academic significance and engineering value. In this paper, systematic investigation of theory and wind tunnel tests has be adopted to study the mechanism of generating internal pressure, the coupling effect of internal pressure and flexible roof and the solving method of response of roof structures induced by wind-induced internal and external pressure of the buildings.In aspect of theoretical research, iterative algorithm is used to estimate orifice damping of the structures with single windward opening in turbulent flow. The characteristics of orifice damping are analyzed and the factors influencing orifice damping ratio are found. Frequency-domain analysis of the internal pressure fluctuation for structures with arbitrary windward openings is developed and opening ratio is newly defined. The newly defined opening ratio is used to evaluate internal pressure fluctuation and the merit is definite. The transfer equations of the internal pressure at dependence against to the external pressure considering the background porosity are derived. Additive damping effect of the background porosity is clarified theoretically and relevant quantization index is obtained. A three-order dynamic differential equation for principal oscillation modal of closed roof structure is deduced considering the influence of internal pressure and the roof-internal pressure coupling equation system for principal oscillation modal of the roof structures with single windward opening is developed and corresponding frequency response matrix is offered. Then the frequencies and damping characteristics of the flexible roof andcoupling vibration system with wind-induced internal pressure are analyzed profoundly. Finally, the coupling dynamic theory is used to induce the modal analysis method for the dynamic response of roof structures induced by wind-induced internal and external pressure.In aspect of experimental research, a series of low-rise building models with various opening areas, opening positions and internal volumes are designed and multiparameter comparison wind tunnel tests are conducted. The space distribution characteristics of the wind-induced internal pressure are reported and the production mechanism of the wind-induced mean internal pressure and the fluctuating internal pressure are studied. Theoretical methods for estimating the mean and the root-mean-square internal pressure coefficients are introduced. Through analyzing time histories of the wind pressure coefficients, the rules of selecting peak factors of the internal pressure and the correlation coefficients of internal-external pressure are extracted. An aeroelastic model of adjustable stiffness roof structure is designed adopting cable-membrane architecture and the wind tunnel tests for wind-induced dynamic response of the roof structure with various opening conditions are conducted. The variance laws for wind-induced response of the roof structures in respect with various factors are studied, and the frequency and damping characteristics of the roof structures with windward openings are analyzed. The wind tunnel test results agree well with theoretical ones.Finally, the similarity problems of the wind tunnel test considering the wind-induced internal pressure are discussed. The additive criterions for simulating pneumatic stiffness and orifice damping are deduced based on theoretical analysis and corresponding processing methods are offered. Based on national and international suggestions of wind load codes currently and the findings in this dissertation, a suit of structural design rationalization suggestions considering wind-induced internal pressure is proposed.