Research On Stability And Progressive Collapse Of Double-layer Reticulated Shell Structure Under Strong Snow Load

In recent years,due to the influence of various natural disasters or human factors,accidental loads have become an important reason for the continuous collapse of large spatial structures.Since the collapse of apartment buildings in London in 1968,various countries have promulgated the anti-collapse design methods successively,and put forward the relevant norms to improve the anti-continuous collapse ability of structures.The research on collapse resistance started late in China and a large number of researches with practical engineering background are still needed to provide theoretical basis for the formulation of relevant standards.Continuous collapse has become the focus of research by scholars.In this paper,the practical work of a double-layer reticulated shell is as follows:(1)Based on the eigenvalue buckling analysis,the distribution area of the sensitive bars was preliminarily judged,and the load which will causes complete collapse of the structure and the importance factor of the bars in the structure,which was named as sensitivity at here,were carried out from four aspects,including material strength,section size,initial defect and supporting mode.Analyze the stability of the remaining structure after dismantling of the rods as well as the original structure.Using this method can we obtain the ultimate bearing capacity of structure as well as the sensitivity of the robs.After that,the factors which will affect the sensitivity of the robs are also analyzed,and the accuracy of the eigenvalue buckling analysis method to verify the sensitive link is verified,which makes preparation for the subsequent dismantling of the component method.(2)Adopts the form of the partition exert to consider a variety of snow load distribution,combining with the existing research results and the structure symmetry,the load distributions were reduced to six to improve the efficiency of the analysis,the use of general auxiliary software STADS automatically guide the load function to simulate the spatial structure on the surface of all kinds of load to load node to four weeks,Determine the most sensitive position of the double-layer reticated shell structure under the snow load distribution,further understand the stability of the structure,and determine the priority dismantled component position in the subsequent collapse resistance analysis.(3)The anti-continuous collapse performance of a double-layer reticulated shell model under non-uniform snow load was studied based on the demolition method.The SAP2000 simulation software is used to realize the nonlinear quasi dynamic time-history analysis,and the corresponding analysis flow chart is proposed.The analysis steps and modeling ideas are described,and the dynamic amplification coefficient and the importance coefficient are introduced as the indexes of structural collapse resistance analysis.Through the study of failure path,it is found that the collapse failure mode of double-layer reticulated shell can be defined as the asymmetric collapse caused by the failure of the bar near the support,which verifies the importance of the bar near the support.(4)It provides a method to enhance the collapse resistance of the double-layer reticulated shell by increasing the section size of the components in the sensitive area.Compared with the original structure from the aspects of sensitivity,stability bearing capacity,importance coefficient and dynamic amplification coefficient,the performance difference between the reinforced section structure and the original structure is discussed.Several measures are proposed to enhance the anti-collapse performance of the structure,including strengthening the connection form of joints,vigilance against the influence of uneven settlement of bearings,reasonable selection and prevention of accidental events,etc.