Numerical simulation of compression bending bearing property of concrete filled steel tubular support joints

Aiming at the problem that the joints of concrete filled steel tubular support under eccentric compression load in deep roadway are easy to fail as weak parts, the mechanical bearing property of casing connection joints and flange connection joints under compression bending load is analyzed by using ABAQUS numerical simulation software. Based on the M_u-N_u curve under compression bending load, the influence laws of the parameters of the casing connection joints and the flange connection joints are analyzed respectively, and the parameter design suggestions of different types of joints in the support are given. At the same time, the bearing property of different types of joints is compared and analyzed according to the optimal parameters of the casing connection joints and the flange connection joints. The results show that: ① the strength grade of concrete is the important influencing factor of the compression bending bearing capacity of the joints, the greater the degree of eccentricity, the less obvious the influence; with the change of the degree of eccentricity, the influence of casing length, casing wall thickness, casing gap, the number of bolts and flange thickness on the compression bending bearing capacity is changed; ② With the increase of casing length, the increase of casing wall thickness and the decrease of casing gap, the compression bending bearing capacity of casing connection joints increases; with the increase of the number of bolts and flange thickness, the compression bending bearing capacity of the flange joints increases, and the strength grade of the bolts has no obvious influence on the compression bending bearing capacity; ③ Under the bias condition, the bearing capacity of the casing connection joints is significantly lower than that of the member without a casing or flange, and the equal strength connection cannot be realized. The load-displacement curves of the flange connection joint are similar to that of the member without a casing or flange, and the bearing capacity only decreases by about 1.7% under the bias condition; ④ The ultimate bearing capacity and stiffness of the flange connection joints are better than that of the casing connection joints, which is a kind of strong connection joint. The degree of load eccentricity and support joints parameters have a significant impact on the bearing capacity of the support. The flange connection joints have good bending bearing capacity and should be applied to the support joints. The research results can provide suggestions for the design of concrete-filled steel tubular support joints in order to give full play to the bearing property of the support.