Recent worldwide applications of fiber reinforced polymers (FRP) wraps and tubes for existing and new structural members have continued to emphasize the significance of confined concrete. This study presents an overview of the related finite element (FE) studies for, but not limited to, the FRP-confined concrete applications of commercial FE programs such as ABAQUS and ANSYS. The capabilities, limitations, and remarks of the concrete models available in the programs are addressed. When the built-in options cannot be satisfied, several recommendations are also given for the user-defined concrete material models. The needs for future research and developments are also indicated.

A two-stage analytical model for evaluating the stress-strain behavior of square concrete columns confined with glass fiber-reinforced polymer (GFRP) is proposed. Fifty-one square columns (divided into seventeen groups) were tested under static axial compression up to failure. The main factors considered in the test are as follows: grades of concrete, bonding shape, amounts of GFRP jackets, and space of fiber strips. The results clearly showed the efficiency of the GFRP jackets in enhancing the ultimate strain and the strength of the columns. The analytical model was calibrated using data from the tests, and good agreement between test and computation results was obtained.

It has been widely known that concrete filled steel tubular (CFT) columns have much higher strength and deformation capacities than common reinforced concrete (RC) columns because of beneficent interactive confinement effect between the filled concrete and the steel tube. The confinement effect by steel tube furthermore contributes to improving ductility of high-strength concrete, and enables application of the CFT columns in high-rise buildings located on seismic regions. This paper describes the axial and the flexural behaviors of CFT columns with circular and square sections based on many experimental researches conducted in Japan. The emphasis of this paper will be placed on the stress-strain curve models for concrete in CFT columns, which play the fundamental role in assessing both of the axial and the flexural behaviors of the CFT columns.

Eleven approximate full-size specimens including nine eccentrically compressed columns of monotonic loading and two axially compressed columns of laterally cyclic loading were tested. By a series of comparison experiment of specimens strengthened using a kind of composite mortar laminates reinforced by mesh reinforcements (CMMR laminates) and no strengthened specimens, it was found that the RC columns strengthened with attached CMMR laminates demonstrated greater degree of improving in load-bearing capacity, in which the carrying capacity increment of the strengthened eccentrically compressed columns with lesser eccentricity was greater than that of the same type of columns with bigger eccentricity under the same strengthening conditions; the strengthening effects of the specimens with lower concrete grade are better than that of those ones with higher concrete grade; the ductility and the deformation capacity and energy dissipation ability of the strengthened columns were remarkably increased. In this paper, the test results is described, the principle and regularity that this category of strengthening laminate improved the ultimate load-bearing capacity, ductility, cracking behavior and mode of failure etc. of the RC columns are analyzed. The studying results proved that this strengthening measure for RC columns is superior to make the strengthening effect notable, working behavior of strengthened column excellent, strengthening construction easy and economical.

Theoretically sound empirical models for the axial stress-strain behavior as well as the transverse deformation behavior of concrete with constant confinement under uniaxial compression loading are proposed based on plasticity theory using existing empirical models and test data in the literature. The proposed axial stress-strain model provides strength and ductility increases with increasing confining pressure. The confining pressure is applied in the model as an initial hydrostatic compression loading region. The proposed empirical transverse deformation model uses the plastic strain rate as a function of the axial strain to provide a basis for quantifying the compaction and dilation behavior of confined concrete under uniaxial loading conditions. Concretes with various compressive strengths are considered in combination with confining pressures up to 50% of the unconfined concrete strength. Parameters needed to describe the axial and transverse deformation behaviors are identified and their recommended values are provided.