Abstract
This paper investigates the crucial design parameters for the prediction of the ultimate axial compressive deformation of reinforced concrete columns externally confined with fiber reinforced polymer (FRP) materials. Numerous test results of available columns with a square and rectangular section under cyclic axial loading were gathered in an advanced database. Herein, the database is enriched with necessary design parameters in order to address the unique tensile strain field variation of the FRP jacket. Since there is a lack of consequent recording of the FRP strain field in existing experiments, three dimensional pseudodynamic finite element analyses results from several characteristic cases of tested columns are utilized to address this gap. Therefore, a hybrid experimental–analytical database is formed, including several critical FRP strains, steel strains and deformations. A modified model is proposed to predict the ultimate axial strain for reinforced concrete columns externally confined with FRP materials. The proposed model aims to address indirectly the effects of the internal steel cage, concrete section shape and of their interaction with the external FRP jacket on the critical tensile strain of the FRP jacket at failure of the column. The predictive performance of the model over the available tests of (reinforced concrete) RC columns under cyclic compression is remarkably improved when compared against the performance of other existing models. It provides predictions with average ratio (AR) of 0.96 and average absolute error (AAE) of 36.5% and therefore may contribute to safer seismic resistant redesign.
Highlights
The use of fiber reinforced polymers (FRPs) has been widely accepted as a successful confinement technique for existing reinforced concrete (RC) columns in buildings and bridges
The behavior of concrete columns confined with FRP has been extensively studied, leading to a significant number of stress–strain models, some focused on circular cross-sections [1,2,3,4,5] and others focused on square and rectangular ones [6,7,8,9,10,11,12,13,14,15,16,17]
Fanaradelli et al [28,29] investigated all available stress and strain models of the literature against all available test results through an extended database and concluded that with suitable modifications, several existing design models for plain concrete columns of rectangular section confined with FRPs could provide reliably the maximum and ultimate axial stresses for the corresponding concrete columns with internal steel reinforcement, subjected to monotonic or cyclic axial loading
Summary
The use of fiber reinforced polymers (FRPs) has been widely accepted as a successful confinement technique for existing reinforced concrete (RC) columns in buildings and bridges. Fanaradelli et al [28,29] investigated all available stress and strain models of the literature against all available test results through an extended database and concluded that with suitable modifications, several existing design models for plain concrete columns of rectangular section confined with FRPs could provide reliably the maximum and ultimate axial stresses for the corresponding concrete columns with internal steel reinforcement, subjected to monotonic or cyclic axial loading. Fanaradelli and Rousakis [35] conducted advanced 3-dimensional pseudodynamic FE analyses and investigated the variation of the FRP strain field throughout loading of RC columns for different characteristic tests available in the literature to address missing design parameters These columns were modeled and analyzed under axial concentric loading–unloading–reloading cycles of increasing compressive deformations. The proposed model is compared against the experimental results of numerous RC columns under cyclic loading and its performance is satisfactory
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