Cyclic Behaviour of Lateral Ties Confined Polyolefin Fibre Reinforced Concrete under Repeated Axial Compression

Abstract

Although various models exist for envelope curves of concrete confined by transverse reinforcement, only a few simple models represent the hysteretic behavior of the confined concrete; therefore, development of stress–strain model of unloading and reloading paths for confined concrete is needed. In this paper, an experimental and numerical investigation for describing the cyclic stress–strain behavior of lateral ties confined and polyolefin fibre reinforced concrete (CPFRC) prisms under repeated axial compressive loading is presented. The study focuses on the effect of repeated unloading and reloading cycles on confined concrete prisms. The combined effect of spacing of lateral ties and volume fraction of polyolefin fibres was studied both experimentally and numerically from the point of deformability characteristics of concrete under repeated loading as loading, unloading and reloading.The envelope curve is derived from the results of uniaxial, monotonic, compression loading tests specimens. It explicitly accounts for the effects of lateral tie spacing of 145mm spacing and 75mm spacing and polyolefin fibres of volume fractions 0.7% and 1.2% on concrete prisms of size 150 ×150 ×300 mm were investigated. The behaviour is implemented in the finite element program in ANSYS software, with a view to analyzing CPFRC prisms under repeated loading. This analysis accounts for energy dissipation through hysteretic behavior, stiffness degradation as damage progresses, and degree of confinement. It was observed from hysteretic behavior that for increased polyolefin fibres volume fractions the degradation of strength and stiffness reduces significantly.