Experiment On Properties Of Load Carrying Capacity Of FRP Confined Reinforced Concrete Columns

In recent years, FRP has been widely used in the field of retrofit of concrete structures due to its excellent mechanical behavior. It is the fit using style that FRP is used to confine concrete. As a result of FRP confinement, both the compressive ability and ductility of concrete can be greatly enhanced.At present, many researchers have been studied on the FRP confined concrete and abtained many conclusions and valuable test data. At the same time, the problems of the studies on the FRP confined concrete are found. The first problem is the study on the cross section of columns, most researches have mainly concentrated on the shape of circle cross section of short columns, few square cross section studies are reported. In order to reduce the problem of stress concentrate, this paper proposed a new cross section named elliptical modified rectangular. The second problem is the study on the method of caculating and the reliability of the FRP confined concrete column, although there are many researchers studying on the method of caculating of the FRP confined concrete, they did not accord. The publications on reliability of the FRP confined concrete column are relatively few. The third problem is the study on the stress-strain curve, the problem focus on the parameter which can exactly reflect the relationship of the geometry character and the physics character of FRP and concrete. The fourth problem is that in contrast to the large available database on short RC columns wrapped with FRP, publications on slender columns under eccentric loading are relatively few. This limits the applications of RC columns wrapped with FRP. In order to investigate the behavior of slender reinforced concrete (RC) columns sufficiently confined with FRP, more research work is needed. It is, therefore, useful to study the load carrying capacity of RC slender columns sufficiently confined with FRP and thus to understand the characteristics of the columns with a large slenderness ratio.To get a better understanding of the square section reinforced concrete columns wrapped with FRP under axial loading, eight specimens were tested. The results show that the stress-strain curve of square section, which is characterized by the transition zone is longer, is different from of circle and elliptical section. At the same time, the theoretical reseach work had been done with the software ABAQUS. The ABAQUS analyses include the circle and elliptical section specimens, considering the strength of concrete and layers of FRP. The caculated results are compared with those from experiment and they agreed well with each other. The problem about the parameter which can exactly reflect the relationship of the geometry character and the physics character of FRP and concrete is present is discussed and the applicability of the confinement stiffness ratioβj is proved. Based on the above argument and a lot of test data, the fomular of parameters of stress-strain curve of different section specimens are proposed. The stress-strain curves which are caculated by bringing the proposed the fomular of parameters into the model of Richard and Teng J.G are compared well with the experiment stress-strain curves.Before the study on the behavior of slender reinforced concrete columns sufficiently confined with FRP under eccentric loading, we must get a better understanding of FRP confined concrete slender columns under axail loading. So ten elliptical section slender columns and nine square section slender columns are tested. The stable coefficient of specimens is abbtained and the fomular of load carrying capacity of FRP confined slender columns is proposed.Because of many slender columns in the structure under eccentric loading, the study on them is necessary. Twenty elliptical section slender columns and eighteen square section slender columns are tested. The augment coefficient of eccentric distant is discussed and the fomular of load carrying capacity of FRP confined slender columns under eccentric loading is proposed. The simplified fomular of load carrying capacity of FRP confined slender columns under eccentric loading is also proposed, which is deduced by the method of experience coefficient.At last, in order to analyse the reliability of the proposed fomulars of load carrying capacity of FRP confined slender columns under axial and eccentric loading, we compile a program using the software MATLAB according to the method of JC. The caculating results show that the relatility satisfy the need of the concrete criterion.