Research on Interface bond strength and bond-slip constitutive models for rectangular CFST columns

Abstract

Abstract. More recent studies have suggested that parameters such as cross-section type, cross-sectional dimensions, interface length, concrete compressive strength, slenderness ratio, steel strength, roughness of interface, concrete casting style, and concrete curing conditions potentially have some influence on the value of the bond strength. In this paper, a brief review of previous research and literature that are pertinent to the present study of the interface bond strength and τ-S constitutive models are presented first. According to the previous laboratory testing results, three equations are designed to calculated are average elastic limit bond strength, average ultimate bond strength and average post-peak residual bond strength, respectively. Moreover, a new simplified four-part model has been proposed to describe the τ-S response. IntroductionThe steel-concrete interface bond stress is the force being on the interface between the steel tube and the concrete core. It is the guarantee to assure the concrete and steel tube to work together. In the beam-column joint area, shearing force from the beam translates to the steel tube of the column through the beam-to-column connection. Then, it is gradually translated into the core concrete through the steel-concrete interface bond stress. The value of interface band strength can influence the load transfer to a certain extent and it is the key point for the individual differences of different calculation theories. Parameters such as cross-section type, cross-sectional dimensions, interface length, concrete compressive strength, slenderness ratio, steel strength, roughness of interface, concrete casting style, and concrete curing conditions potentially have some influence on the value of the bond strength [1][2][3][4][5][6]. Previous research on the bond strength versus slip (τ-S) constitutive model is relatively small. Previous Laboratory Testing for Interface Bond StrengthThe earliest research on the interface bond strength of rectangular CFST columns was carried out by Virdi and Dowling in 1975 [1]. A push-out test programme applied to 88 circular CFT columns were conducted to investigate the value and the composition of the bond strength. It was found that the bond strength did not appear to be greatly influenced by the variation in the concrete cube strength. In 1991, push-out tests have been carried out on 36 CFST stub columns by Shakir-Khalil [7]. The tests showed that the push-out load is a variation upon or function of the shape of the steel hollow section, as well as also a variation or function of the type of shear connectors and the way in which the load is applied to the steel section.In 1993, a further experimental study on the interface condition as applied to the interface bond strength was investigated by . Six out of twelve of square CFST columns and six out of twelve circular columns were tested by means of oiling the steel-concrete interface. The results of the tests indicated that oiling the steel-concrete interface resulted in its halving ...