Size Effect Analysis Of Concrete Columns Retrofitted By BFRP

The research of fiber reinforced composites(referred to as FRP) in the field of civil engineering began in the 1960 s of last century. Subsequently domestic and foreign scholars have made deep research on the performance of concrete beams, columns, nodes, and frameworks retrofitted by FRP. But the research mainly concentrated on scale models reinforced by FRP, whether the test data and calculation model can reflect the mechanical properties of large components in the actual engineering structure, namely the research of size effect on components retrofitted by FRP is still relatively little. Size effects can not be ignored,however, the study of size effect on components retrofitted by FRP is not sufficient, and conclusions are not the same. Therefore, depth study on size effect of FRP reinforced concrete members has high theoretical significance and engineering value.This paper carried out research aiming at size effect of concrete columns retrofitted by BFRP, using finite element software ANSYS. The main research work and research results were as follows:(1) Simulating and analysing axial compression performance of 30(total 5 group) plain concrete columns retrofitted by BFRP and 30(total 5 group) reinforced concrete columns retrofitted by BFRP, and analysing the influence of varing factors of BFRP confinement ratio and column length-diameter ratio on size effect. The results showed that for plain concrete columns retrofitted by BFRP, confinement ratio and length-diameter ratio had no influence on size effect of stress- strain curve, turning point strength, ultimate strength, turning point strain,ultimate strain and dissipation capacity. For reinforced concrete columns retrofitted by BFRP,confinement ratio had part impact on strengthening phase of stress-strain curve, ultimate strength and dissipation capacity, but had no size impact on turning point strength, turning point strain and ultimate strain; length-diameter ratio also had no impact on size effect of stress- strain curve, turning point strength, ultimate strength, turning point strain, ultimate strain and dissipation capacity. For both plain concrete columns retrofitted by BFRP and reinforced concrete columns retrofitted by BFRP, BFRP had little effect on turning point strength and turning point strain, but can significantly increase ultimate strength, ultimate strain and dissipation capacity of columns.(2) Aming at reinforced concrete columns retrofitted by BFRP, using factorial analysis method in mathematical statistics to analyze test data. The results showed that specimen size and confinement ratio had great influnce on ultimate strength, but their interaction had no effect on ultimate strength; specimen size, confinement ratio and their interaction significantly influenced dissipation capacity.(3) Aming at constraint ratio of retrofitted columns in 0.40 ~ 0.16, proposing ultimate strength prediction model when considering size effect; aming at constraint ratio of retrofitted columns in 0.32~0.40, proposing energy dissipation prediction model when considering size effect. By verification, these two prediction models were all in good agreement with finite element simulation data.