Nonlinear analysis of circular concrete-filled steel tubular short columns under axial loading

Abstract

a b s t r a c tThe confinement effect provided by the steel tube in a circular concrete-filled steel tubular (CFST) short column remarkably increases the strength and ductility of the concrete core. The reliable prediction using nonlinear analysis methods for circular CFST columns relies on the use of accurate models for confined concrete. In this paper, accurate constitutive models for normal and high strength concrete confined by either normal or high strength circular steel tubes are proposed. A generic fiber element model that incorporates the proposed constitutive models of confined concrete is created for simulating the nonlinear inelastic behavior of circular CFST short columns under axial loading. The generic fiber element model developed is verified by comparisons of computational results with existing experimental data. Extensive parametric studies are conducted to examine the accuracy of various confining pressure models and the effects of the tube diameter-to-thickness ratio, concrete compressive strengths and steel yield strengths on the fundamental behavior of circular CFST columns. A new design formula accounting for concrete confinement effects is also proposed for circular CFST columns. It is demonstrated that the generic fiber element model and design formula adequately predict the ultimate strength and behavior of axially loaded circular CFST columns and can be used in the design of normal and high strength circular CFST columns.

Nonlinear analysis of axially loaded circular concrete-filled stainless steel tubular short columns

“…It is noted that the confining pressure model proposed by Liang and Fragomeni [16] can be used for concrete confined by high strength steel tubes with significant strain hardening and has been verified by experimental results [15,27]. In addition, it has been used to simulate the behavior of confined concrete in circular CFSST columns with acceptable accuracy [22].…”

“…The general stress-strain curve for confined concrete in circular CFST columns suggested by Liang and Fragomeni [16] is shown in Fig. 3.…”

“…Fragomeni [16] using the strength reduction factor c  as follows: Based on the work of Hu et al [12] and Tang et al [32], Liang and Fragomeni [16] proposed an accurate confining pressure model for normal and high strength concrete in circular CFST columns, which is adopted in the present numerical model as follows: …”

“…Numerical models have been developed to study the behavior of circular CFST short columns under axial loading [11][12][13][14][15][16][17][18]. However, there have been relatively limited numerical studies on the behavior of axially loaded circular CFSST short columns.…”

“…The effects of diameter-to-thickness ratio, concrete compressive strength and stainless steel proof stress on the behavior of circular CFSST short columns are investigated. A design model based on Liang and Fragomeni's formula [16] is proposed for the design of circular CFSST columns and compared with test results and design codes.…”