Strut-and-Tie Model and Numerical Simulation of Sleeve Grouting Connection for Concrete-Filled Steel Tube Column

Abstract

To study the performance and failure mechanisms of concrete-filled steel tube (CFST) column sleeve grouting connections, theoretical analysis and finite element simulation were performed for the structure in the connection. In this paper, a theoretical strut-and-tie model suitable for calculation of the axial compression capacity of sleeve grouting connections was proposed. High-precision numerical models were established to verify the applicability of the strut-and-tie model and the rationality of parameter selection in the sleeve grouting connection. The parameters include the shear key height, shear key shape, shear key distance, and grouting material strength. The results showed that the prediction values of the strut-and-tie model accorded well with the experimental values and simulated values. The average ratio of the calculated values based on the ACI and EC2 codes to experimental values were 1.07 and 1.09, respectively. An increase in the shear key height can improve the axial compression capacity of the sleeve grouting connection, and it was suggested that the range of the shear key height was reasonable at 2~3 mm. The shear key shapes of semicircular, rectangular vertical and trapezoidal were recommended, which can meet the requirements of sleeve grouting connections of CFST columns. The load-transmitting behavior of rectangular vertical shear keys was better due to the insignificant stress concentration. The rectangular horizontal form of shear keys is not recommended since it has the worst load transmission. The shear key height-to-distance ratios were recommended to be 0.044~0.1, the amplitude of the strength attenuation was different only after failure, and all models showed good ductility and compression capacity. With the increase in grouting material strength, the axial compression capacity of the sleeve grouting connection increased. It is reasonable to use grouting material strengths C50 to C90 for the sleeve grouting connection.