Concrete-filled Rectangular Hollow Section Columns Research Articles

Investigations into Structural Behavior of Concrete-Filled RHS Columns with Unequal Flange Thickness under Compressive Load.

Previous studies have shown that components with an unequal-walled concrete-filled rectangular hollow section (CFRHS) can achieve a greater resistance under bending than those with equal-walled CFRHS. However, the study on the compressive behavior of the CFRHS column is limited. Therefore, this paper investigates the performance of compressed CFRHS columns with unequal flange thickness, based on experimental and numerical approaches. In the test, the effects of slenderness and eccentricity on the compressive capacity of the CFRHS columns with unequal shell thickness are discussed. Numerical models based on the finite element method are established, to evaluate the resistance and failure pattern of each specimen in the test. Parametric studies are carried out based on the validated model, to investigate the effect of eccentricity, wall thickness, and steel and concrete material properties on the load-bearing capacity of the compressed CFRHS column. In addition, the analytical expressions of the resistance of CFRHS columns with unequal wall thickness are derived, and the prediction values are validated through comparing with the test results. It is found that eccentric compressed columns with unequal-walled CFRHS have a similar load-bearing capacity and better ductility when compared with the equal-walled CFRHS.

Component-based mechanical models for axially-loaded through-diaphragm connections to concrete-filled RHS columns

This paper presents the results of theoretical studies into the behavior of the through-diaphragm to concrete-filled rectangular hollow section (RHS) columns subjected to tensile force. Component-based models have been developed and used for predicting the strength of the column component of concrete-filled RHS columns under tensile load imparted through a through-diaphragm connection. The strength models are based upon defining a rigid plate deformation pattern for the column face and then applying the virtual work principle, taking into account the membrane action and strain hardening. The hand calculation procedures for yield and ultimate deflection were also developed. The load–deformation curve consists of three segments: the first representing the elastic behavior from the classic plate theory, the second obtained by plotting the deformation at the ultimate strength against the maximum load, and the third a horizontal line stretching to the failure point. The mechanical models were compared with a large range of experimental results and good agreement was shown between them. The proposed method can be used in the component-based method for connections involving a through-diaphragm component in tension.

Performance of concrete-filled RHS columns exposed to fire on 3 sides

The behaviour of concrete-filled steel tubular (CFST) columns subjected to uniform fires has been well studied over the past few decades. However, knowledge of the performance of concrete-filled rectangular hollow section (RHS) columns exposed to fire on 3 sides, which is a common scenario in practice, is limited. Hence, this paper presents an experimental and numerical study into the response of concrete-filled RHS columns subjected to 3-sided fire exposure. Three full-scale concrete-filled RHS columns, two of which were exposed to fire on 3 sides and the other on 4 sides, were tested to failure. The temperature distributions, axial displacements, lateral displacements and failure modes were all recorded and discussed. Following the experiments, a sequentially coupled thermal–stress numerical model was developed, featuring heat transfer analysis and stress analysis. The FE model was validated against the test results, and used to assist in the understanding of the observed failure mechanisms and to extend the investigated range of key parameters. These parameters included load ratio, load eccentricity, cross-sectional dimensions, slenderness ratio, steel ratio and strengths of the constituent materials. It was found that the load ratio, cross-sectional dimensions and load eccentricity have a significant influence on the fire resistance. Based on the results of the parametric studies, a simplified design formula was developed for predicting the fire resistance of concrete-filled RHS columns subjected to 3-sided exposure. Furthermore, a reduction factor method was proposed for the design of concrete-filled RHS columns exposed to 3-sided fire, based on fire safety design methods for concrete-filled RHS columns in uniform fire, which may be more convenient for engineering applications.