Ductile Concrete Columns Enabled by Multilayer Basalt TRM Shells: Confinement Mechanism and Modeling

Abstract

One typical application of textile-reinforced mortar (TRM) is as a confining material for concrete. The compressive behavior of TRM-confined concrete is often predicted by referring to the models of fiber-reinforced polymer (FRP)-confined concrete. Such reference may be inappropriate because TRM with apparent axial stiffness and nonlinear stress–strain behavior differs from linear elastic FRP. This paper first presents the experiments and analyses of the results to reveal the confinement mechanism of basalt TRM (BTRM) and then proposes an analysis-oriented stress–strain model for BTRM-confined concrete. Twelve compression tests were carried out on concrete columns with and without BTRM and with different textile layers (0–4 layers). Deformations of the BTRM shells and the concrete cores were measured in parallel to understand the mechanical behaviors of the shells/cores and their interactions during loading, i.e., confinement mechanism. The BTRM shell not only improved the compressive strength and the ultimate strain due to the confinement effect but also provided axial resistance through shear stresses at the core–shell interface. Both effects were quantified by a newly established model of which the key novel feature is the updating of the confinement pressure equations based on a careful description of core–shell interactions. The confinement pressure induced by the BTRM shell is separately evaluated in elastic and damaging stages differentiated by the cracking of the mortar matrix. The accuracy of the proposed model is confirmed through comparisons with new test data.