Investigation Of Spherical-Roof And Curved-Roof Subjected To Thunderstorm Downbursts

Thunderstorm downburst is an outburst strong wind spread from the center to periphery on or near the ground, produced a transient strong wind and caused a high near-surface wind velocity, and has caused numerous structural failures around the world. Thunderstorm downburst has become a international hot issue in field of strong wind loads. Currently, the wind field characteristics of thunderstorm downburst have a more comprehensive understanding, while studies on its effect on the structures was relatively rare, especially for the long-span roof, wind tunnel tests and numerical simulation for buildings subjected to thunderstorm downburst have not been reported before. This paper reports investigations of spherical-roof and curved-roof under thunderstorm downbursts by experimental studies and numerical simulation.The field characteristics of thunderstorm downburst are significantly different from boundary layer winds, so the commonly used wind-resistant design can not be applied to thunderstorm downburst. Therefore, in this paper considering the general structure firstly, the theoretical expression of horizontal static wind load consistent with the habit of wind-resistant design were proposed, as well as the wind pressure height coefficient, and the calculation of shape coefficient obtained from wind tunnel testing or numerical simulation methods were well concluded. This work were the basis for the specific study on the impact of long-span roof subjected to downburst and the future practical application.After the establishment of downburst load theory, wind tunnel tests on wind pressure distribution of spherical-roof and curved-roof under thunderstorm downburst were carried out. The scaled models were designed and manufactured according to the similarity criteria, The wind field of downburst was simulated by utilizing an impinging jet to generate a flow blowing to a flat plate. Pressure distributions of roofs had been investigated by varying the parameters of structure, from which the sensitivities of structural parameters such as height-span ratio, rise-span ratio, roof span and wind direction were summarized. Besides, the results were compared with the results of boundary layer wind tunnel. Furthermore, by varying the location of the roofs in the tree-dimensional wind field, the experiments of the wind pressure distribution of the roof were also conducted to reveal the significant effects caused by vertical wind of downbursts.Establishing a full scale wind tunnel of thunderstorm downburst via numerical simulation, and taking roofs the same size with experimental study as the research objects, the impact of long-span roofs subjected to thunderstorm downburst had been investigated by verying the parameters of structure and downburst, simulation results were compared with the results of wind tunnel.This paper will not only enrich the existing theory of thunderstorm downburst wind field, the results will also provide valuable test data and research experience for pressure characteristics of long-span roof under thunderstorm downburst, and ultimately provide the basis for the development of relevant norms.