Cyclic and monotonic behavior of FRP confined concrete rectangular prisms with different aspect ratios

FRP confinement of concrete columns is one of the most common methods for enhancing both the strength and ductility. The optimal design of the FRP confined concrete rectangular columns requires a good comprehension of their cyclic and monotonic stress-strain behavior. In this study the results of the tests on 18 rectangular prisms with different aspect ratios are presented and the effects of this parameter on cyclic and monotonic:behavior of prisms are investigated. Test results indicate that for prisms with different aspect ratios, the monotonic stress-strain curve is approximately tangent to the upper boundary of the cyclic stress-strain curve. Other important results of this study are linearity of relationship between the plastic strain and the envelope unloading strain, the independence of the plastic strain and stress deterioration ratio from the aspect ratio, increase of the axial strain in the early stage of unloading paths, fixation of the plastic strain after repetition of 8 cycles and expansion of the failure area as a result of a decrease in aspect ratio. Examination of the ultimate condition of rectangular prisms (specimen's failure) shows that the FRP hoop rupture strains of the prisms are smaller than the one obtained from tensile coupon test and also when a prism is under monotonic loading, the ultimate axial strain and confined concrete strength are smaller than when it is under cyclic loading. (C) 2012 Elsevier Ltd. All rights reserved.