Behavior Of Steel Tube Columns Research Articles

Parametric Study on the Behavior of Steel Tube Columns with Infilled Concrete—An Analytical Study

Concrete-filled steel tube (CFST) columns are used in tall buildings and bridges, and they provide more rigidity and higher bearing capacity, but buckling affects their behavior. There is an exceptional need to study the behavior of these columns under various conditions. The numerical method is beneficial in supplementing the experimental works and is used to explore the effects of various parameters because of the limitations in cost, apparatus, and time of the experimental program. The various parameters, such as the different slenderness ratios, i.e., column-height-to-cross-section-dimension (H/D), different steel-tube-thickness-to-column-dimension (D/t), and different compressive strength of concrete to yield strength of steel tube ratio (fc/fy) under concentric axial loading are considered in this current study. Firstly, a finite element model used the “ANSYS” software program and was constructed to validate the results of the experimental works. The extensive numerical models were carried out to extensively widen the study in this field. The numerical work was conducted on sixty-four specimens. Moreover, the analytical calculations from the different international codes/standards were compared with the numerical results to test their reliability in predicting the ultimate carrying loads. The study provided results that show the improvement effect of CFST columns with the high compressive strength of infilled concrete, while no remarkable enhancement effect with the high yield strength of steel tube was observed. Increasing the columns’ diameter is more effective in enhancing the load capacity (about three times more) than increasing the tube thickness (about 1.3 times). Ring stiffeners for long CFST columns (H/D > 12) do not lead to any enhancement of the column behavior due to yielding occurring firstly at the location of the rings. ECP205-2007 is the most conservative design code in predicting the load capacity of CFST columns, while the AIJ design code is good at predicting the ultimate load failure compared to the other codes/standards. Eurocode 4 provides underestimation values of the load-carrying capacity of CFST columns.

Eccentric loading behavior of steel tube columns filled with steel‐fiber‐reinforced recycled concrete

AbstractA comprehensive study focuses on the eccentric compressive behavior of steel‐fiber‐reinforced recycled concrete filled steel tube (SRCFST) columns. A total 39 stub columns are tested, and the variables include eccentricity ratio (e/r), steel fiber volume, quality replacement rate of recycled aggregate, concrete strength grade, and diameter–thickness ratio of steel tube. Failure mode, the load–lateral deflection behavior and the moment–curvature response are analyzed. The load–moment interaction relationships, the load–strain responds and the neutral axis position are researched. The results show that the use of recycled aggregate causes the little‐to‐no influence on the eccentric loaded performance of SRCFST columns with a relative smaller e/r. However, the ultimate load and deformability of the columns with higher e/r both decreases rapidly. Adding steel fibers can offset this adverse effect. The addition of steel fibers sustains a higher relative compression region height in the cross section. The ultimate load descent of SRCFST columns due to the increase of e/r is slower than ordinary concrete filled steel tube and recycled aggregate concrete filled steel tube columns. Moreover, on the basis of the unified theory, a calculation model is proposed to predict the ultimate capacity of SRCFST columns under combined loadings. The model captures well the compressive response of SRCFST columns.

Behavior of steel tube columns filled with steel-fiber-reinforced self-stressing recycled aggregate concrete under axial compression

Abstract Faced with the large annual output of construction and demolition waste, cyclic utilization of recycled coarse aggregate (RCA) is inevitable. This study uses steel-fiber-reinforced recycled aggregate concrete (RAC) in the manufacture of concrete-filled steel tube columns, to improve the utilization of RAC. A comprehensive study of the axial behavior of 54 steel-fiber-reinforced self-stressing recycled aggregate concrete-filled steel tube (SSRCFST) columns was conducted. The variables in the experiments included the steel fiber content, self-stress, quality replacement rate of RCA, concrete strength grade, and steel tube thickness. The experimental results show that a poor concrete strength is obtained with increasing RCA content. However, under tri-axial stress in the steel tube, the negative influence of RCA is weakened. An enhancement of the ductility of SSRCFST columns can be achieved by adding a moderate amount of steel fiber. Self-stress can significantly improve the ultimate capacity and stiffness of SSRCFST columns. Moreover, design equations for the ultimate capacity of SSRCFST columns are proposed, and the predictions agree satisfactorily with the experimental results.

Material and structural response of steel tube confined recycled earthquake waste concrete subjected to axial compression

This paper reports on an experimental study of the mechanical properties of recycled aggregate concrete (RAC) and the structural behaviour of steel tube columns filled with RAC subjected to axial compressive loading. A total of ten specimens were tested to investigate the influence of the steel tube configuration (circular or square), the type of concrete (normal concrete or RAC) and the proportion of recycled coarse aggregate (RCA) used in the RAC. The mechanical properties of RAC and RAC columns confined by steel tubes were studied for RCA replacement ratios of 0, 25, 50, 75 and 100%. The results show that RAC may give a slightly lower strength during the first 28 d of curing. However, the ultimate strength (90 d curing) of steel tubes filled with RAC was slightly higher than those filled with normal concrete. The load-carrying capacity of circular steel tube columns filled with RAC was found to be higher than that of square section tubes. Theoretical calculations of the load-carrying capacity of the concrete-filled steel tube columns are presented and compared with experimental results.