Experimental Investigation on SSTT Confined Concrete with Low Lateral Pre-tensioning Stresses

An experimental and analytical study on the application of Steel Strapping Tensioning Technique (SSTT) confinement on twelve high-strength concrete cylinder specimens with dimension of 100 mm and 200 mm in diameter and height respectively has been studied and presented throughout this paper. The specimens were volumetric-identically confined with two different confining materials of different mechanical properties and lateral pre-tensioning stresses, namely SSTT(HC) and SSTT(SS). All concrete specimens were tested under uniaxial compression load. The performance of SSTT-type confined specimens were studied through their stress-strain relationship upon the longitudinal and transverse deformation, mode of failure, level of lateral pre-tensioning stress, and dilatancy behaviour. The results show that high-strength concretes confined with SSTT would significantly reduce the brittleness problem and at the same time, enhancing both ultimate compressive strength and ductility up to 65% and 344%, 36% and 269% for both SSTT(HC) and SSTT(SS), respectively. Those specimens confined with higher lateral pre-tensioning stress exhibits smaller radial expansion and higher rate of axial strain, able to slow down the dilation of confined specimens under loading and thus, helps in enhancing the compressive capacity and ductility. In addition, an analytical comparison between SSTT-type confinement and conventional confinement models have been presented and the results show a linear relationship between the compressive strength enhancement and confinement ratio. Current experimental results were also validated by comparing the observed stress-strain relationship proposed by Mander.