Experimental Study On Wind Load Characteristics Of A Long-span Annular Cantilevered Roof

The long-span cantilevered roof structures are widely used in stadiums,airports,stations,terminals and other buildings for its capacity providing larger space without columns.To highlight local characteristics and meet specific functional requirements,these structures usually have some unique constructions and beautiful shape,but at the same time,they are very sensitive to wind load owning to their longer span,lighter weight,smaller rigidity and lower natural frequency,so the effects of wind load on their safety shouldn’t be ignored during the structural design process.The current load code for the design of building structures only provides the shape factor of wind load on several simple roof structures for engineering reference and indicates that the wind tunnel tests should be conducted for more complicated long-span roof structures to determine the wind load distribution regularity.Based on the actual project of a sports center in Hunan province,three experiments on the wind-load distribution characteristics of the long-span annular cantilevered roof were conducted and the relevant results were presented in this paper.Firstly,the double-side pressure-measuring wind tunnel test on the rigid model of the cantilevered roof was carried out in terrain B according to the actual layout of the project.The results show that both the upper and lower surfaces are subjected to wind suctions and show same tendency with the change of wind directions.The net mean wind pressure coefficients are small for roof located in upstream and the negative value is found on the roof located in downstream,so the whole roof is generally subjected to lift force.The coefficients of RMS for net fluctuating wind pressure in windward area of the inner edge for roof located in downstream are much larger than other areas.The net minimum wind pressure coefficients reach maximum value in the windward area of the inner edge of roof located in downstream as well.Secondly,the wind load distribution characteristics on roof surface were compared before and after the slots between different roofs were blocked.The results show that the variation tendency with wind directions for mean lift force,RMS of fluctuating lift force,minimum lift force and corresponding net value on upper and lower surface are not changed whether the slots are blocked or not,but the concrete numerical value are influenced.When the slots are blocked,the RMS of net fluctuating lift force would increase slightly while other lift force would decrease.The effects of roof slots on distribution regularity of wind pressure in inner,middle and outer edge of the roof are related to the location and wind directions.Finally,the double-sided pressure-measuring wind tunnel tests were carried out for the rigid model of cantilevered roof of the stadium in three wind fields A,B and C to study the influence of the different landforms on the wind load distribution characteristics.The results indicate that variation tendency with wind directions for mean lift force,RMS of fluctuating lift force,minimum lift force and corresponding net value on upper and lower surface are not changed by landforms category but the numerical value are affected in some extent.The change of landforms has little effect on net mean lift force coefficients on roof surface,but has a certain influence on RMS coefficients of net fluctuating lift force and net minimum lift force coefficients,both of which get larger values in landform B and C than A.The change of landform has little effect on the net mean wind pressure coefficients in different areas of roof,both the RMS coefficients of net fluctuating wind pressure and net minimum wind pressure coefficients get larger values in landform B and C than A when the roof were located in downstream.