Experimental study and theoretical prediction of axial compression behavior in PMC-reinforced CFST columns with void defects

Abstract

Polymer-modified concrete (PMC) is a promising seismic reinforcement material to improve the ultimate load carrying capacity and ductility of structures. This study investigates the reinforcing effects of PMC on voided concrete-filled steel tube (CFST) columns through axial compression tests on 21 specimens. A meticulous analysis, incorporating void arch height, steel tube thickness, and PMC reinforcement, elucidates failure modes, load-deformation behavior, and strain characteristics. The experimental results demonstrate that PMC reinforcements significantly enhance the structural behavior and load-bearing capacity, improve ductility, and prevent material detachment from excellent bonding and collaborative working properties. A novel calculation model for ultimate load capacity and lateral pressure coefficient of voided CFST columns is developed and validated. Results reveal a distinct improvement in specimen performance post PMC reinforcement, with load-displacement curves resembling intact specimens, mitigating the impact of void defects. Furthermore, PMC-reinforced specimens exhibit effective recovery of load-bearing capacity and ductility, offering a cost-effective alternative to steel tube thickening. Changes in strain and Poisson's ratio curves underscore PMC's ability to restore biaxial compression stress, enhancing stability. Prediction models, rooted in the Double Shear Unified Strength Theory, accurately anticipate ultimate bearing capacity and lateral pressure coefficient, bolstering practical engineering design and repair endeavors. In summation, this study provides comprehensive insights into PMC-reinforced voided CFST columns, facilitating informed structural enhancements and repairs.