Behaviour of steel straps confined concrete column with lateral pre-tensioning stresses under uniaxial cyclic compression

The behaviour of high strength concrete (HSC) under uniaxial cyclic compression load is extremely important to simulate the seismic effect. It is very helpful to the development of high rise building and future demand of HSC. The main problems of HSC are brittle and less ductile. Hence, this project focuses into the brittleness and ductility of HSC column subjected to uniaxial cyclic compression. Eighteen specimens with compressive strength of C60, 100mm in diameter and 200mm in height were tested and analysed under uniaxial cyclic and monotonic compression loads. All the specimens were confined with 2 layers or 4 layers steel straps with pre-tensioning stress at 10mm spacing between straps. The lateral pre-tensioning stresses for 2-layer and 4- layer confinement were fixed to 5bars and 4bars respectively. The results show that SSTT confinement enhances the strength, less brittle and more ductile compare to unconfined specimen. The compressive strength and ductility enhancement are up to 118.5% and 64.5% respectively. The envelope curve of confined HSC tested under uniaxial cyclic loading is almost coincides with the curve of identical specimen tested under uniaxial monotonic load. The graphs of plastic strain confined with 2-layer and 4-layer confinement show the different in gradient. This indicates that plastic strain of SSTT confined HSC depends on the layers of confinement and level of pre-tensioning stress