Study On Damage And Failure Of Single-layer Reticulated Dome Under Downburst

The long-span space structure is a wind-sensitive structure,which is easy to be damaged under extreme wind loads.Downburst is a kind of special wind load,which is caused by strong downdraft in thunderstorm cloud reaching the ground and forming strong radiation wind.This strong wind has a strong destructive force on long-span space structures.At present,the failure law of large-span spatial structures subjected to downburst and the evaluation method of the structure’s performance against downburst are still lacking.Aiming at the problems existing in the current research,this paper takes the K8 type single-layer spherical reticulated shell structure as an example to study the failure rule and vulnerability of the structure under the action of downburst.The main research contents and conclusions are as follows:（1）The downburst wind field was simulated based on the deterministic-stochastic hybrid model.Wood vertical wind profile model and Holmes empirical model were used to simulate the mean wind,and the autoregressive model based on Davenport spectrum was used to simulate the fluctuating wind.The linear elastic model of a K8 single-layer reticulated dome was established based on the vector form intrinsic finite element,and the elastic time-history analysis of the structure was carried out.Then,the dynamic characteristics and displacement time-history responses of the single-layer reticulated dome under the action of the downburst wind field were investigated.（2）Considering the geometrical nonlinearity and material nonlinearity of the structure and the failure criterion of elements,the progressive collapse of structures with different rise-span ratios under the action of downburst is simulated.The failure law of single-layer reticulated domes under the action of downburst wind field is explored by studying the influence of downburst mean wind load and total wind speed load on the failure mode of the structure when the rise-span ratio is 1/3,1/5 and 1/7,respectively.The results show that the failure of a single-layer spherical reticulated shell structure under the action of a downburst wind field is mainly caused by the buckling of space rods.The mean wind of the downburst plays a dominant role in influencing the structure and it determines the failure mode of the structure,while the pulsating wind section intensifies the response of the structure and causes the failure time to be advanced due to the principle of dynamic magnification.In addition,with the increase of the rise-span ratio,the shape coefficient and wind area of the structure change,and these changes will affect the failure mode of the structure.（3）In view of the lack of wind disaster fragility analysis methods for long-span spatial structures,a fragility analysis process for single-layer reticulated domes under the action of the downburst was proposed by referring to the seismic and wind disaster fragility analysis methods,and the rationality of the analysis process was illustrated by a numerical example.The method based on the random IDA,considers the uncertainty of the downburst and structural parameters,and the incremental dynamic analysis was carried out.According to the existing vulnerability analysis theory,the analysis results of the structure was calculated to create the structural fragility function and fragility curve,so that the performance of the structure against downburst was evaluated.