Abstract: In order to study the damage evolution process of concrete-filled square steel tubular frame exterior joints strengthened with carbon fiber sheet under earthquake, based on the destructive tests of four groups of concrete-filled square steel tubular frame exterior joints strengthened with carbon fiber sheet under low cyclic loading, the influence of seismic damage was considered by the method of material performance reduction. The finite element software ABAQUS was used to simulate the seismic damage of concrete-filled square steel tubular frame exterior joints strengthened with carbon fiber sheet. The improved two-parameter seismic damage model was used to calculate the damage index and to examine the damage evolution characteristics of the specimens. The results show that the method of simulating seismic damage by reducing material properties is reasonable and effective. The selected seismic damage model can quantitatively analyze the damage index of the structure at each stage. The obtained damage evolution curve proves that the carbon fiber sheet can effectively reduce the seismic damage degree of the concrete-filled square steel tubular frame edge joints. Compared with the unreinforced joint specimens, the seismic capacity of the joint specimens strengthened by a carbon fiber sheet is stronger, and the seismic capacity of the earthquake-damaged reinforced joints is also significantly restored.

Key words: CFRP-strengthened, concrete-filled square steel tubular column-steel beam frame joint, seismic damage, damage evolution process