Buckling behavior of a circular steel tube with a bolt–ball joint under installation eccentricity

Abstract

An issue that frequently occurs during the installation of a spatial grid structure is that the tube exhibits bending under installation eccentricity, and the buckling stability of the tube significantly decreases. In the study, eccentric compression tests of circular steel tube with a bolt–ball joint are carried out, in which three types of joint specifications and three types of installation eccentricities are considered. The degradation characteristics of the buckling stability of circular steel tubes under different installation eccentricities are obtained via tests. Similar phenomena of tube buckling are observed under different installation eccentricities. Additionally, detailed finite element models with bolt threads are established via ANSYS. A comparison of simulation and test results indicate good agreement, and this confirms the validity of the numerical simulation method. Then, a total of eighteen simulation schemes for the buckling behavior of tube under different eccentricities are studied, regarding three different joint specifications with six tube specifications for each. The results indicate that the stability capacity decreases in an approximate linear manner with respect to the installation eccentricity in the range of 0–15 mm, which is consistent to the test results, and the decreasing speed slightly drops while the eccentricity goes large. A reduction factor is proposed as the reference for considering the reduction of stability capacity of the tube under different eccentricities in engineering design.