Transverse compressive behavior of plain and polypropylene fiber-reinforced concrete infilled steel tubes as hybrid steel-concrete nodes for discrete reticulated shell structures

This study investigates using concrete infilled steel tubes as hybrid nodes for discrete reticulated shell structures under compressive loading transverse to the tube axis. Three configurations were tested: empty, plain concrete infilled and polypropylene fiber-reinforced concrete infilled steel tubes. Displacement-controlled loading was applied through welded steel plates. Simplified beam theory models and nonlinear finite element analysis were used to evaluate the structural behavior. The concrete infilled steel tube specimens had higher stiffness and load-bearing capacity than the empty ones. The structural behavior of the concrete infilled specimens could be split into pre- and post-split-tensile cracking phases. No significant difference was found between the plain and fiber-reinforced concrete specimens under loads up to 1500 kN, which was the load limit of the testing machine. An additional fiber-reinforced concrete specimen, tested on a higher capacity machine, had a load-bearing capacity of 2400 kN and exhibited ductile failure. • The infilled specimen's structural behavior can be divided into pre- and post-split-tensile-concrete infill cracking phases. • The infilled specimen's stiffness decreases after cracking but remains higher than that of empty specimens. • No notable difference between plain concrete and polypropylene fiber-reinforced concrete infilled steel tubes. • Beam theory models and nonlinear finite element analysis adequately describe the specimen's structural behavior. • The failure mode of a transversely compressed polypropylene fiber-reinforced concrete infilled steel tube is ductile.