Journal:Engineering Structures

Key Words:Circumferential gap (CG) at the steel-concrete interface is a critical imperfection in concrete-filled steel tubular (CFST) members, impairing composite action and reducing load-carrying capacity and ductility. This paper presents a comprehensive study on the effectiveness of pressure grouting for rehabilitating such defects in CFST stub columns. A total of twenty specimens, including intact columns, CFST columns with circumferential gaps (CG-CFST), and their grout-rehabilitated counterparts, were tested under axial compression, considering two concrete grades. The results show that gap imperfections reduce the ultimate strength by 9–37% and induce brittle failure due to delayed concrete confinement. Conversely, the grouting technique successfully restores composite interaction, enabling the rehabilitated specimens to recover 99–106% of the intact strength and, compared with the intact CFST counterparts, exhibit significantly enhanced ductility. As the first systematic application of pressure grouting for rehabilitating circumferential gap defects in CFST columns, this method effectively eliminates the adverse effects of interfacial gaps and restores structural performance to a level comparable to that of intact members. A validated finite element analysis (FEA) model is developed to simulate the behavior, and subsequent analysis of the internal mechanisms reveals that the grout layer's primary role is to transfer interfacial stresses rather than carry axial load, providing detailed insight into the internal load-transfer mechanism. An extensive parametric study using the validated FEA model quantifies the influences of concrete and steel strengths, gap ratio, and grout properties. Critically, the grout strength is found to have a negligible effect on the rehabilitated capacity within the practical range studied. Based on these findings, a practical and simplified design equation is proposed to predict the axial compressive capacity of grout-rehabilitated CFST stub columns, offering engineers a reliable tool for practical applications.

Indexed by:Journal paper

Page Number:2026,368:123681

Translation or Not:no

Included Journals:SCI

First Author:靳萍

Co-author:任泽林,姜航

Correspondence Author:叶勇