Mechanical performance study of the retractable pier column after stiffening

To solve the problem that the overlapping parts of a retractable pier column are prone to damage, this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe. To study how the stiffener-ring parameters influence the mechanical properties of the pier column, 12 scale model specimens (including nine specimens with stiffener-ring widths of 40, 50, and 60 mm and three unstiffened comparison specimens) were tested under axial compression. Based on the test results, the specimen load–displacement, load–deflection, and load–strain curves were analyzed, and a finite-element model of a pier column under axial compression was established to determine the optimal stiffener size. The results show that setting a stiffener ring enhances the cooperative working ability between the steel pipe and the internal filling material and restrains the lateral deformation of the pier column, thereby improving the ultimate bearing capacity and overall stability of the pier column. The ultimate bearing capacity of the pier column is related to the width and thickness of the stiffener ring. The optimal size of the stiffener ring of the model pier column is 70 mm in width and 4 mm in thickness. The present research results provide a reference for designing compressible pier columns and column stiffening in mines and have important practical significance.