Study On Wind-induced Dynamic Response And Wind Load Factor For Long-span Flat Roof Structures

Along with the development of science and technology, a number of long-span flexible roof structures with beautiful shapes and new structural systems are widely applied into the public constructions, for example, gymnasium, hangar and theater. When wind flows around roofs, the airflow will be separated to form a high suction zone, and the flexible roofs will suffer from wind-induced buffeting response. So far, a limited number of research papers are related to dynamic responses of long-span flexible roofs at home and abroad. So it is important to study on wind load and wind-induced dynamic response for long-span flexible roof structures in the field of engineering and research.Based on wind tunnel test and theoretical analysis, the vibration mechanism, vibration shape, dynamic response and wind load factor of long-span flat roofs subjected to wind excitation are analyzed systematically in this dissertation, and some valuable results are obtained.In the matter of wind tunnel tests, the rigid and aeroelastic models for long-span flat roof structures in these cases, with or without parapets, closed or unclosed and opening a hole suddenly, are designed. The question that wind pressure upper surface and under surface of rigid models can be tested at the same time and the flexible vinyl tubes connected to pressure taps can't influence the turbulence is solved commendably. The method to simulate the aeroelastic properties of prototype in consideration of a series of similarity coefficients including Froude number is established. Through the wind tunnel tests for rigid and aeroelastic models, the aerodynamic pressure coefficients and dynamic responses are obtained for these long-span flat roof structures. And a comparative analysis is also performed.In the matter of theoretical analysis, using the local mean wind pressure coefficients and time history of fluctuating pressures determined in wind tunnel, the wind-induced dynamic responses for long-span flat roof structures are calculated infrequency domain and time domain separately. Based on the comparison of the computed results and experimental dates, some important conclusions can be obtained. The results obtained from the analysis method in time domain agree with experimental dates much better than the results obtained from the spectral analysis method. The quasi-static assumption can not be adopted in the analysis on wind-induced dynamic responses for long-span flat roof structures. The rules of dynamic responses obtained by the spectral analysis method are similar to those obtained by the analysis method in time domain, but the value is much larger. So the spectral analysis method based on the quasi-static assumption is modified in the present study. Finally, the wind load factor of long-span flat roof structures is discussed, and an important piece of advice is inferred from it. For engineering design, it is better to use wind load factor defined the ratio of wind-induced total displacement to static displacement for computing the equivalent static wind load of long-span flat roof structures. And the formula to calculate the wind load factor is provided when the stiffness of the roof varies.