Behavior Analysis Of Single-layer Spherical Reticulated Shell Under The Combined Action Of Fire And Shock

With the development of technology and the improvement of human cognition,large-span steel structures in daily life are becoming more and more common,such as various exhibition halls and warehouses.Most of these places are crowded with people when holding large-scale events.Once the structure is damaged,it will cause immeasurable consequences.However,there are various forms of structural damage,such as structural collapse caused by component damage during construction,and fire and explosion of surrounding buildings,resulting in damage to the structure due to the impact of high temperature and heavy objects.Therefore,it is of great significance to study the collapse failure behavior of large-span steel structures.Based on the finite element software ABAQUS,this is mainly studies the K8 single-layer spherical reticulated shell as follows:(1)Firstly,the definition of continuous collapse of structures is defined,and the design methods of anti-continuous collapse adopted in the codes of various countries are introduced and summarized.At the same time,the method suitable for the analysis in this paper is selected,that is,the method of dismantling components.(2)Combined with the model used in this paper,the specific steps of K8 single-layer spherical reticulated shell collapse performance were explained in detail by the method of dismantling components,and the finite element analysis flow chart was given.(3)The sensitivity analysis of the reticulated shell structure is carried out by using the dismantled members.Through the analysis,it can be seen that the sensitivity of the inner ring of the reticulated shell structure is greater than that of the outer ring under the condition of a certain span ratio and load ratio For the rods at different positions on the same ring,the hoop rods have the greatest sensitivity,the radial rods have the least sensitivity,and the diagonal rods are in the center.Through sensitivity analysis,the key components in the reticulated shell structure were determined.Based on this,the dynamic response of the reticulated shell after the removal of the key components was studied under different load ratios and span ratios.The research shows that under the condition of a certain rise-span ratio of the reticulated shell structure,with the increase of the load ratio,the damage degree of the reticulated shell structure gradually increases.When the load is relatively small,the reticulated shell structure does not change significantly.The shell is easy to restore the original equilibrium state.With the increase of the load ratio,the equilibrium position of the reticulated shell changes,and each node vibrates freely near the new equilibrium position under the action of external load.When the load ratio increases to the extent that the reticulated shell structure cannot be carried,the continuous collapse of the reticulated shell structure will occur,and the damage will gradually expand outward from the place where the component is removed.The continuity failure phenomenon can be clearly found through the node displacement curve.Through analysis,it can be seen that the reticulated shell structure can lead to progressive collapse if only one key component is removed,although the structure members with dense arrangement of single-layer grid-like structure provide greater redundancy for the whole structure.(4)The fire heating curve used in the large-span space structure is introduced,and the temperature load distribution of the reticulated shell structure members under the fire source selected in this chapter is given.At the same time,the basic methods and principles of the impact problem are introduced.(5)According to the damage and failure criterion of steel,this study applies the finite element software-ABAQUS to analyze the failure modes of the Kiewitt-8 single-layer reticulated domes subjected to blast loading at different fire stages,considering the influence of heavy impact and temperature of fires on the steel property.Based on the case studies of 693 domes,six failure modes and their distributions under four different temperatures are classified according to the vertical displacement and the plasticity status of the rod under peak impact load.The results show that the temperature of fires has a great influence on the stability of the reticulated domes under impact load.Given the mass and velocity of the impingement,when the temperature approaches to a critical value,the reticulated domes collapsed totally.When the maximum temperature of the reticulated domes reaches 400?,the impact resistance capability of the structure significantly decreases.As the mass and velocity of the impingement increase,the deformation mode of the reticulated domes does not vary with the increase of the temperature,and the failure type of reticulated dome is dominated by shear failure.