Axial Compression Behavior of Square RC Columns Confined with Textile-Reinforced Ultrahigh-Toughness Cementitious Composite Jackets

Textile-reinforced ultrahigh-toughness cementitious composite, referred to as TRU, is an innovative strengthening system that has superior crack resistance and durability compared with textile-reinforced mortar. This paper presents an axial compression experimental study of RC square column specimens confined with TRU jackets to understand the combined confinement behavior of TRU jackets and stirrups. The effects of the number of textile layers and stirrup ratios were analyzed with respect to failure modes, load-bearing capacity, and deformation behavior. The experimental results showed that all the jacket specimens failed in jacket rupture, and TRU jackets played a significant strengthening role for concrete up to about 50 MPa, particularly for low-strength concrete below about 30 MPa. TRU confinement with four layers of textile could enhance compressive strength by about 40%–58%, along with moderate stress decay plateaus after the peak points for low-strength concrete. A synergistic constraint effect was obtained between stirrups and TRU jackets. Furthermore, a segmented stress–strain relationship model, combined with compressive strength and peak strain models, was proposed for concrete confined by combined TRU jackets and stirrups. The calculated results agreed well with the experimental curves, providing important theoretical support for the application of TRU jackets in the strengthening of RC members.