Abstract
The current paper aims to present the results of an experimental investigation into the compressive strength of pre-stressed steel tube-confined compressed concrete (PSTC) stub columns. Here, to prestress the confined concrete, an innovative technique is utilized, in which the fresh concrete is subjected to compression while the steel tube is simultaneously preten-sioned laterally by applying external pressure to the fresh concrete. A total of 135 confined specimens were tested under axial compressive loading to determine the confinement strength of the specimens. Moreover, new confinement relationships for the load-carrying capacity of the PSTC columns were proposed in terms of the prestressing ratio ( r P ), reference concrete strength ( c f), and tube outer diameter to wall thickness ratio ( / Dt ). Finally, a parametric study was conducted to evaluate the effect that the parameters r P, c f , and / Dt have on the compressive strength of the prestressed confined concrete. The results indi-cate that the confined concrete prestressed by the present technique demonstrates significantly enhanced load-carrying capacity; however, increasing the prestressing level slightly affects it.
Highlights
Concrete-filled steel tube (CFST) columns have been widely used in many engineering structures in that the CFST columns combine the best characteristics of both steel and concrete materials including high strength, high ductility, and high stiffness (Dundu 2012)
This study proposes an innovative technique in order to create active confinement in the steel tube-confined concrete (STCC) columns, in which the steel tube prestressing and the concrete compressing are both carried out simultaneously by applying pressure on the fresh concrete
Based on the experimental results of this study, the following conclusions may be drawn: 1. The confinement effectiveness coefficient value of the non-prestressed steel tube-confined concrete (NPSTC) in the proposed relationship is about half of that in Richart’s model and is nearly 0.5 to 1 times that of the Mander’s
Summary
Concrete-filled steel tube (CFST) columns have been widely used in many engineering structures in that the CFST columns combine the best characteristics of both steel and concrete materials including high strength, high ductility, and high stiffness (Dundu 2012). In the STCC columns with passive confinement, the steel tube has no initial lateral stress, for an effective confinement, a large deformation of the concrete core in the lateral direction and in the axial direction is required This fact increases micro-crack formation in the concrete. This study proposes an innovative technique in order to create active confinement in the STCC columns, in which the steel tube prestressing and the concrete compressing are both carried out simultaneously by applying pressure on the fresh concrete. This technique was first proposed by Nemati (2006), subsequently employed and investigated by Nematzadeh (2012). The results of this research indicate that the confined concrete prestressed by the present technique demonstrates significantly improved load-carrying capacity
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