Compressive behavior of shrinkage-compensating UHPC-filled steel tube lattice columns

This study proposes a novel shrinkage-compensating ultra-high performance concrete-filled steel tube (UHPCFST) lattice column system that addresses two critical limitations in UHPC applications: cost reduction achieved by eliminating steel fibers while incorporating coarse aggregates, and enhanced structural efficiency through composite tubular lattice configuration. Axial compression tests on eight specimens comprising five UHPCFST lattice columns, two CFST lattice columns, and one hollow steel lattice column, were performed to evaluate the effects of three key parameters: concrete strength, steel fiber content, and steel tube thickness. Numerical simulations using refined finite element model were conducted to complement experimental investigations. The key test findings reveal that increasing steel tube thickness and adding steel fibers effectively reduced post-peak load degradation, while 130 MPa UHPC-filled specimen demonstrated 25 % and 79 % higher ultimate capacity than 30 MPa concrete-filled and hollow steel tube specimens, respectively. The parametric analysis based on numerical simulations identifies the diameter-to-thickness ratio as the dominant factor, with the ultimate capacity increasing 416.8 % when the ratio increases from 10 to 26.7.