Moment Stability Analysis Of Large-span Roofs Under Random Wind Action

The large-span roof structure is sensitive to wind loads,and its wind resistance performance analysis has always been a hot and difficult point in the study of wind resistance of civil engineering structures.The components of the large-span roof structure may be destabilized under strong wind,causing local collapse or overall collapse of the structure.However,the current research on the wind stability of large-span roofs is not enough,and the influence of the randomness of wind loads on stability is less considered.Based on the stochastic dynamical system theory,studies the stochastic stability of large-span roof structures under wind loads according to the moment stability method.Firstly,the stable boundary conditions of the roof member under random noise excitation are established.According to the random stability domain of the member under the noise excitation,the influence of the wind speed,elastic modulus and cross-sectional area of the member on the random dynamic stability of the member is established.Then,based on the wind model test data of the rigid model,the wind load spectrum model of the roof bar is fitted,and the method of calculating the random stability domain of the roof bar under wind load is established,and a double-layer cylinder is realized.The wind-induced random stability of the reticulated roof is carefully analyzed.The research in this paper mainly includes the following three aspects:(1)According to previous studies,the quasi-constant assumptions are not applicable to large-span roof structures.The quasi-stationary assumptions for wind-stability calculations of large-span roof will produce large errors.So the Davenport wind load spectrum fitting method based on the quasi-stationary assumptions can not be applied to large span roof structures.Based on the modeling theory of the power spectral density function of the wind load of the large-span roof,combined with the wind pressure time-history data of the wind tunnel test of the double-layer reticulated shell model,the wind-loads power spectral density function of the rods of the roof are obtained.(2)According to the kinetic theory,the differential equation of lateral vibration control of the simply supported member under the axial force is obtained,and then transform the differential equation into Ito? stochastic differential equation according to the coefficient function expression of the Ito? stochastic differential equation.Finally,based on stochastic dynamical system theory,the stochastic stability boundary function of the member under dynamic load is obtained by the moment stability method.After obtaining the stochastic stable boundary function of the member,the previous research cases are substituted into the obtained boundary conditions,and the calculation results are compared with the previous research results to judge the reliability of the boundary function.Then the stochastic stability domain of the simply supported member under the action of noise excitation and wind load is calculated,and the influence of variables such as wind speed,elastic modulus and cross-sectional area of the member on the random dynamic stability of the member is preliminarily determined.(3)Substituting the wind load spectrum model of each member into its stochastic stable boundary condition,the stability of the reticulated shell structure under different wind direction angles is obtained by the physical parameters of the double-layer reticulated roof.And the influence of parameters such as wind direction angle,wind speed,elastic modulus and cross-sectional area of the member on the wind-induced random stability of the roof is further studied.It is found that the most unfavorable wind direction angle of wind-induced random stability of double-layer cylindrical reticulated shell is 105o,and the influence of wind speed change on structural stability is most obvious under 105o wind direction angle.Under different winds direction angle,the increase in wind speed has a consistent effect on the stability of the same member.The larger the cross-sectional area of the rod,the more obvious the effect on increasing the stability of the rod.