Compression behavior of square and circular SFRC columns confined with external steel straps

Abstract

Steel-Strapping Tensioning-Techniques (SSTT) have been proposed recently as a confinement strategy to enhance the strength and deformation capacity of new and existing Reinforced Concrete (RC) columns. Main advantages of SSTT are the low cost, simple installation and modest installation time. Existing methods to quantify the increase of the compressive strength and deformation capacity of actively confined concrete have been obtained considering conventional deformed steel. Additionally, previous studies have observed that toughness and deformation capacity of concrete increase when adding steel fibers to the concrete matrix. However, the combined effect of SSTT applied to Steel Fiber Reinforced Concrete (SFRC) columns has not been assessed. Hence, the objective of this study is to evaluate the compressive behavior of SFRC columns confined with SSTT. A total of 34 short columns with SFRC and plain concrete were subjected to monotonic compression tests. The studied variables consider the cross-section of the columns (square and circular), the steel fibers dosage (15, 30 and 60 kg/m3), 3 ), and the spacing of the steel straps (37.5, 50 and 75 mm). The obtained results demonstrate that the SSTT increased the compressive strength between 4 % and 18 %, and the deformation capacity up to 800 %. Additionally, the use of steel fibers was effective in further increasing the deformation capacity of columns confined with SSTT. A numerical model based on a database of 150 tests, where 34 are from this study, is also proposed to predict the compressive behavior of SFRC columns confined with SSTT.