SEISMIC PERFORMANCE OF HIGH-STRENGTH CONCRETECOLUMNS CAST IN STAY-IN-PLACE FRP FORMWORK

摘要

The use of high-strength concrete (HSC) in seismically actively regions poses a major concern because ofthe brittle nature of material. The confinement requirements for HSC columns may be prohibitivelystringent since they require proportionately higher confinement than columns of normal-strength concrete.An alternative to conventional confinement reinforcement is the use of fiber reinforced polymer (FRP)casings, in the form of a stay-in-place formwork, which can fulfill multiple functions of; I) formwork, ii)confinement reinforcement, and iii) protective shell against corrosion, weathering and chemical attacks.This paper investigates the use of stay-in-place FRP formwork as concrete confinement reinforcement forHSC columns with square and circular cross-sections. Large-scale specimens with 270 mm cross-sectionaldimension and 90 Mpa strength concrete, were tested under constant axial compression and incrementallyincreasing lateral deformation reversals. FRP casings were manufactured from carbon fiber sheets andepoxy resin. One of the square columns was equipped with internal FRP crossties, a new techniqueintroduced by the authors, to provide well-distributed lateral restraints along the column face, therebyimproving the mechanism of confinement. The results indicate that the deformation capacity of HSCcolumns can be improved significantly by using FRP casings. The results further indicate that theconfinement effectiveness of FRP-confined square sections can be substantially increased with the use ofFRP crossties.