6 - Rubberized CFDST short columns

Abstract

This chapter provides the experimental behavior and design of rubberized square and circular short concrete-filled single skin and double skin steel tubes under concentric axial compression. Double skin steel tubes of 0%, 15%, and 30% rubber replacements were concentrically developed and tested. The rubber particles were treated with sodium hydroxide solution, resulting in an increased bonding strength to the concrete. With regard to the circular sections, a total of 15 composite specimens were examined to ascertain the varying properties of single skin, double skin, confined, unconfined, standard, and rubberized concrete. Recycled rubber particles ranging from 2 to 7mm in size were used to replace 15% and 30% of the fine and coarse concrete aggregates by weight, respectively. The compressive strengths were theoretically determined and compared with those measured experimentally. An interesting spring-back phenomenon occurred in which the infill rubberized concrete moved upward after testing due to the large confinement of the core and elasticity of the rubber. Confinement in RuCFDST showed significant improvements in the strength and ductility properties. The experimental results proved to be in agreement with the design’s ultimate axial strength predictions proposed by the existing methods and design codes. Given the exceptional ductility, energy dissipation, and improved strength of RuCFDST, this study shows the potential viability of RuCFDST as structural columns, particularly in areas that are prone to seismic activity, security bollards, and flexible road side barriers. An innovative, confining, stress-based design for RuCFDST is additionally provided at the end of this chapter.