Structural behaviour of high-strength concrete column confined with steel strapping tensioning technique subjected to constant axial and lateral cyclic loads

Abstract

Ductility is the main consideration in designing reinforced concrete (RC) structures. The application of high-strength concrete (HSC) in columns is able to reduce the column sizes and optimize the floor area of a building. Besides, reduction in building self-weight can minimise the seismic load acting on the building. Established Steel Strapping Tension ing Technique (SSTT) by previous researchers was chose n in this study due to its low material cost and ability to enhance the ductility of HSC. This research is conducted to study the effectiveness of SSTT in improving the ductility and deformability of HSC columns subjected to constant axial load and reversed cyclic horizontal loading which represents simulated seismic excitation since SSTT is yet to be tested under cyclic loading. A series of experimental work consisted often specimens with concrete compressive strength of 35 MPa, 55 MPa and 85 MPa were carried out. The first series of five specimens with 55 MPa were tested with different spac ing of steel strapping confinement. Second group of specimens with 85 MPa were confined with different steel strapping layers and longitudinal reinforcement ratio of 1.78%, 3.56% and 5.12%. The behaviours of concrete columns were presented in hysteresis load-ductility graphs to determine the performance of confined HSC columns. The ductility and defon nability of each columns were compared with the pre-analysed estimations. Results showed that with the increase of steel strapping as confinement, the ductility and shear resistance of HSC column improves significantly according to certain configurations. Ultimate displacement of the 85 MPa specimen was improved from 37.82 mm to 71.52 mm due to SSTT confinement. HSC column is able to achieve the same level of ductility as normal strength concrete column by reducing the spacing of SSTT confinement. The structure behaviours of SSTT-confined HSC columns under simulated seismic load have been examined and SSTT will benefit the construction industry as an alternative solution in confining HSC.