Abstract
Objectives: A model with more generalized scope than those in the literature has been proposed to predict the stressstrain response of Fiber-Reinforced Polymer (FRP) confined rectangular RC columns under axial compression. Methods/ Statistical Analysis: 255 columns with their experimental data were used as a basis for the model expressions. Their database included columns with aspect ratios ranging from 1.0 to 2.0. Furthermore, the cross sectional depth varied from 100 to 500 mm and the unconfined concrete strength varied from 18.3 to 51.5 MPa. Findings: Based on interpretation of the test results, bilinear and post-peak softening stress-strain responses are proposed as referencing models, respectively, for columns having a sectional depth of smaller or larger than 300 mm. The softening model is composed of a parabolic expression for describing the first stage of the response and two linear expressions for the second and third stages. The influences of aspect ratio and size of cross sections, number of FRP layers and internal hoop steel bars on the key features of the envelope stress-strain curve model (i.e. ultimate axial stress and strain) are all considered in the model. Application/ Improvements: Reasonable agreement was revealed between the analytical responses of the proposed model with the selected tested responses, confirming its ability to simulate the stress-strain behavior of FRP-confined rectangular RC columns of small or large sizes. Keywords: FRP-confined Concrete, Rectangular RC Columns, Stress-strain Model
Highlights
The application of Fiber-Reinforced Polymer (FRP) as confinement wraps has been extensively used to retrofit existing concrete columns in bridges and buildings
Due to limited studies available for FRPconfined RC columns of non-circular cross-sections7–9, this paper provides a generalized model considering the effects of internal steel reinforcement and aspect ratio and size of cross-sections
Few models were on FRP-confined RC columns under compressive axial loads10,11 of these studies, a research to propose a model for the axial strength and strain capacities of RC columns with square and rectangular cross-sections confined with CFRP has been performed10
Summary
The application of FRPs as confinement wraps has been extensively used to retrofit existing concrete columns in bridges and buildings. Of the recent studies on rectangular column sections, several column tests under compression loading to study the axial strength and stress-strain behavior of FRP-wrapped unreinforced concrete prisms have been conducted. To the best knowledge of the writers, the influence of column size and internal reinforcement have been only considered for CFRP-confined square RC columns of medium 204 × 204 × 612 mm and large 305 × 305 × 915 mm sizes7 Results of their tests revealed the confinement by the CFRP slightly enhanced the strength of specimens and resulted in either bilinear or a post-peak softening behavior. The influences of column section size and its aspect ratio on the strength and ductility results, effective rupture FRP strain and internal hoop reinforcement were carefully accounted for. Postpeak softening response (section depth > 300 mm) Bilinear response (section depth < 300 mm) εc
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