Axial behavior variation of 72-story concrete-filled steel tubes with different joint connections due to interface debonding considering long-term deformation of concrete core

• Published in: Journal of Building Engineering Vol. 98; p. 111172
• Main Authors: Fu, Xueyi, Yang, Yuanlong, Li, Zhi, Xiao, Congzhen, Xu, Bin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2024
• Subjects: Concrete-filled steel tube (CFST); Connection details; Force transfer path variation; Interface debonding; Long-term axial load-carrying capacity variation; Long-term axial stiffness variation; Long-term axial load-carrying capacity variation; Connection details; Concrete-filled steel tube (CFST); Interface debonding; Long-term axial stiffness variation; Force transfer path variation
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2024.111172

Long-term concrete deformation including shrinkage and creep occurring seriously threats the longevity, safety and serviceability of concrete-filled steel tube (CFST) structures. In this study, numerical simulation on the variation of axial behavior of 72-story CFST structures with different joint connection details due to interface debonding considering shrinkage and creep of concrete core is carried out. Three connection details including connections with inner horizonal diaphragms only, two-direction through-beams only, and inner horizontal diaphragms combined with two-direction through-beam, are considered, respectively. Vertical loading from floors is treated as centralized vertical force applied on steel tube directly. The shrinkage of concrete core is simulated by decreasing concrete temperature. A cohesive constitutive law and a Coulomb friction model are employed to describe the interface behavior in tangential direction before and after debonding, respectively. The interaction between concrete core and steel tube in normal direction is treated as a hard contact. The concrete plastic-damage (CPD) constitutive model is used for concrete core and a plastic constitutive law is employed for the steel tube. The initiation of the interface debonding between steel tube, H-shaped steel beam flanges, inner diaphragms and concrete, the variation of the force transfer path, stress redistribution, steel tube yielding and the final failure are described in detail. Results show that the axial load-carrying capacity of each CFST structure has a decrease of 26–28 % when compared with that determined by the current design code where the confinement effect is considered, and a decrease of 9–10 % when compared with that determined by the current design code where the confinement effect of steel tube is not considered. Moreover, the axial stiffness decreases to 76–78 % of their theoretical values when debonding is not considered. Numerical results show that the interface debonding negatively affects the long-term axial load-carrying capacity and stiffness obviously, which has not been considered in current design codes. Some comments on the design of CFST members are proposed based on the numerical simulation results. •Interface debonding distribution of three 72-story CFST structures with different connection details is illustrated.•Effects of load application path and construction sequency on debonding are considered due to concrete shrinkage and creep.•Variation of long-term axial load-carrying capacity and stiffness under sustained loading due to debonding is carried out.•Force transfer path variation, stress redistribution, steel tube yielding and the final failure pattern are described in detail.•Decrease in load-carrying capacity and stiffness due to interface debonding is confirmed and comparison is made.