Study On Correlation Between Progressive Collapse Resistance And Seismic Performance Of K6 Single-layer Latticed Domes

The failure of local members caused by extreme snow load or earthquake often leads to the progressive collapse of large-span steel structures,which indicates that the failure of some important members may cause the collapse of the structure.Although there are many members in single-layer spatial grid structures,the failure of some key members has a great influence on the progressive collapse resistance and seismic performance of the structure.Therefore,in order to strengthen the collapse resistance of the structure in both cases from the perspective of structural design,it is particularly necessary to study the correlation between the progressive collapse resistance and seismic performance of the single-layer spatial grid structure.In this paper,the dynamic test on the progressive collapse resistance of K6 single-layer spatial grid domes scale model is carried out,and the progressive collapse resistance analysis and seismic analysis of the full-size models are carried out.The main research contents and conclusions are as follows:(1)The single-layer latticed dome scale models with different rise-to-span ratios were designed to carry out the dynamic test of progressive collapse resistance,and the dynamic response of the structure after the instantaneous failure of local member was analyzed.The test results showed that: although compression mechanisms served to inhibit progressive collapse of the K6-6 and K6-8 domes,and they had identical collapse modes: the joint loads were transferred via surrounding localised arch action,and the collapse of the arch following member failure led to the progressive collapse of the latticed domes.The K6-6 dome collapsed slowly and exhibited better progressive collapse resistance.(2)Based on the analysis of the progressive collapse resistance of the full-scale structure,the specific distribution range of important members and the progressive collapse modes after considering the failure of important members were studied.For important member distribution: K6-6 reticulated dome is mainly distributed in the second to fourth ring near the central node.K6-8 reticulated dome is mainly distributed in the third to fifth ring.As for the progressive collapse mode,two kinds of rise-to-span ratio latticed domes have the same progressive collapse mode:(1)when the rib fails,the failure rib is taken as the symmetry axis,and the symmetrical failure mode is caused by the local structure damage connected with its lower end.(2)when the ring rod fails,the failure starts from the small triangle area damage caused by local arch failure,leading to the failure of 1/6 area where the ring member is removed,the damage continues to develop symmetrically to the left and right sides of the 1/6 area,and finally the overall structure damage.(3)Based on the seismic analysis of full-scale K6-6 and K6-8 latticed domes,the distribution range of important members and the collapse mode after considering the failure of important members were studied.For important members: the important members of K6-6 latticed domes are mainly distributed around the third and fourth rings;K6-8 latticed dome is mainly the second to sixth ring rib members.For the collapse mode,the two collapse modes are the same:(1)when the rib bar fails,the complete main rib where the failed rib bar is located is taken as the symmetry axis,and the nodes connected with the lower end of the failed rib bar generate large displacement,which causes the symmetrical failure of the symmetry axis in the local area,and the symmetrical failure continues to expand symmetrically,eventually leading to the complete collapse of the overall structure;(2)When the ring rod failure,from the position of the ring rod and the failure of the joint connected to the bar began to produce a large vertical displacement,causing local failure and spread around,leading to 1/6 of the area where the two main rib failure,extended to the last main rib failure,gradually formed the overall collapse.(4)Contrast and analyze the similarities and differences of the distribution range of important members and collapse modes in the progressive collapse and seismic analysis of single-layer latticed domes,and the correlation between their progressive collapse and seismic performance were studied.For the correlation of important members,K6 latticed domes show that some important members overlap,and some important members are independent of each other.For K6-6 latticed dome,the proportion of overlapping components is 56.25%.For K6-8 reticular dome,the proportion of superposition member is 27.78% of the general importance member.As for the correlation of the collapse mode,considering the failure of local typical important members,the progressive collapse mode of K6 reticulated dome was not changed under the seismic load,and the two collapse modes showed good consistency.(5)The distribution of the comprehensive important members of K6-6 and K6-8 reticulated domes are given,and two comprehensive optimization methods are given according to the distribution range of the comprehensive important members: local members section optimization and local double-layer optimization.Both optimizations can effectively improve the progressive collapse resistance and seismic performance of K6 single-layer latticed domes.