1 EXPERIMENTAL STUDY AND NUMERICAL MODELLING OF SOLID AND HOLLOW FRP- CONFINED CONCRETE MEMBERS

The use of Fiber Reinforced Polymer (FRP) materials as confining devices for concrete columns may produce remarkable increases of strength and ductility, as demonstrated by numerous published experimental and theoretical works [1-4]. On the other hand bridge piers are often designed as hollow-core reinforced concrete (RC) sections to obtain a reduction of the self-weight (especially in seismic zones) and a better structural efficiency in terms of strength/mass and stiffness/mass ratios. In contrast to this popularity in practice, scientific studies on the mechanical behaviour of such structural elements are limited [5], and the use of FRPs for external confinement of hollow core columns and piers is an almost unknown field at the moment. In this research work both solid and hollow-core concrete specimens were tested under uniaxial compression to study the stress-strain relationship before and after FRP jacketing. A range of experimental parameters were investigated: different concrete strength, type of fibers, number of wrap layers, column shape and dimensions, and for square and rectangular sections, the corner radius and the cross-sectional aspect ratio. Circular columns wrapped with FRP showed a significant increase in terms of both strength and ultimate displacements. Rectangular columns showed a lower increase in ultimate capacity, compared to circular sections