Constitutive Models Of Cfrp-confined Reinforced Concrete Circular And Square Columns

Although extensive researches on the stress-strain models of CFRP-confined concrete columns had been carried out around the world, some questions still exist as follow: (1) most of existing researches focused on CFRP-confined plain concrete and didn't consider the effect of reinforcment. (2) subsection mode was adopted to describe the constitutive models of CFRP-confined reinforced concrete circular column. (3) there isn't stress-strain model for CFRP-confined reinforced concrete square columns under medium confinement level. The studies on cyclic axial compression, using for earthquake resistance analysis of structural members, were much fewer. In order to solve above issues, this thesis studies the constitutive models that take the effect of reinforement into consideration through the monotonic and cyclic uniaxial compression experiments of CFRP-confined reinforced concrete circular and square columns. These work provide the technical support for nonlinear analysis of CFRP-confined structures and have important theoretical significance for improvement of seismic Design Code of building. The main contents of the thesis are summarized as follow:1. A total of 20 reinforced concrete circular columns (204 mm in diameter and 612 mm in height) and 18 square columns (204mm in length and 612 mm in height) externally confined with CFRP were tested under monotonic and cyclic uniaxial compression. For circular columns, reinforcment have less effect on stress-stain relationship, but have more effect on square columns and the cyclic compression behavior of circular and square columns. The influence of reinforcement should be considered in stress-strain models of CFRP-confined reinforced concrete circular and square columns.2. The equation of ultimate stress and strain and a new unique stress-strain model were developed for CFRP-confined reinforced concrete circular columns. The rule of unloading and reloading curves in cyclic compression relationship are formed. Combined with monotonic stress-strain model, the cyclic compression model of CFRP-confined reinforced concrete circular column is developed. The predicting results of the proposed model agree well with test datal.3. The standard of describing high-confined, medium-confined and low-confined for CFRP-confined reinforced concrete square column is advised. The equation of stress and strain of feature point and a new stress-strain model were developed for CFRP-confined reinforced concrete square column under medium confinement level. The rule of unloading and reloading curves are simulated based on test results. At last, the cyclic compression model of CFRP-confined reinforced concrete square column is developed considering the monotonic stress-strain model. The predicting results of the proposed model agree well with test data. It shows that the monotonic and cyclic compression models of CFRP-confined reinforced concrete square column under medium confinement level are correct and applicable in the future.