Study On Wind Load Distribution Characteristics And Wind-induced Response Of Umbrella Composite Membrane Structure

Membrane structure has the characteristics of lightness,softness and unique shape,and can meet people’s requirements for long-span,so it is widely used in modern life.But because of light and flexible nature,membrane structure is sensitive to wind.The current technical code for membrane structures(CECS 158-2015)only gives the shape coefficients of some simple membrane structures,while some complex composite tensioned membrane structures need to determine the wind load shape coefficients through wind tunnel tests.At present,there are few wind tunnel tests for composite tensioned membrane structures,and the test cost is high.Therefore,it is difficult to summarize general laws based on existing research results.In this thesis,wind load distribution characteristics and the rule of wind-induced vibration response of umbrella combined tensile membrane structure are studied.Firstly,the wind field around single umbrella,double umbrella combined tension membrane structure and three umbrella combined tension membrane structure is simulated by CFD numerical wind tunnel technology.According to the results of different wind angle and rise-span ratio conditions,the wind load distribution characteristics of membrane surfaces are obtained,and the nephogram of wind pressure coefficient for upper and lower surfaces of umbrella composite tensioned membrane structure under wind load is drawn,and the suggestions on the value of zoning wind pressure coefficient are given.Secondly,the wind speed time history curves of several characteristic points of umbrella tensile membrane structure are simulated based on AR method,comparing the wind speed power spectral density curve obtained by simulation with the target power density curve to verify the correctness of the simulation coding.The wind-induced vibration responses of one single umbrella and umbrella composite tensile membrane structures are calculated by time-domain method,and the influence of wind angle,pretension of membrane and rise-span ratio on composite tensile membrane structural response are analyzed.The conclusions are as follows:(1)The wind-induced displacement responses of the three types of umbrella tensioned membrane structures reach the maximum value at 0° wind angle.At 0° wind angle,according to the structure displacement response from large to small,the three structural forms are sorted into three umbrella combination membrane structure,double umbrella combination membrane structure,single umbrella membrane structure.Except for 0°wind angle,the displacement of the double umbrella composite membrane structure reaches the largest;(2)the change rate of the displacement extremes of the three forms of umbrella tension membrane structure tends to decrease with the increase of membrane initial pretension,indicating that after exceeding a certain pretension,the effect of controlling the displacement of tensioned membrane structure by increasing membrane initial pretension is not obvious.For the common single umbrella and double umbrella combined tension membrane structure with rise span ratio of 1/14～ 1/12,when the pretension increases from 4 k N/m to 5k N/m,the change rate of structural displacement has been less than 2%,it is very unconspicuous to control the structure displacement effect by continuing to increase the pretension;(3)The displacement response of single umbrella and umbrella combined tensioned membrane structures increases with the increase of rise span ratio.Therefore,reasonable rise span ratio should be adopted as far as possible in the design of such tensile membrane structures,in order to avoid the destruction of membrane structures due to excessive deformation under wind load.