Compressive performance of carbon fiber reinforced concrete columns

According to the restraint principle of concrete, under the action of axial force, the concrete cracks and the circular cross section of the concrete increases, which stimulates the strain of the surrounding fibers and generates circular tensile stress. The concrete is placed under pressure on the circumference, thereby improving the compressive strength of the concrete column, and the ductility of the member is greatly improved. It can be seen that the carbon fiber material circumference reinforcement concrete column can effectively improve its axial bearing capacity. When the carbon fiber wrap is used to reinforce the concrete column around the circumference, the use efficiency of the carbon fiber wrap is the highest. Experimental studies have shown that the ductility and ultimate bearing capacity of concrete columns are significantly increased after carbon fiber wrap is used to reinforce the concrete column. The increase effect is significantly related to the number of carbon fiber wrap layers and the distance between the fiber wrap strips. When the number of layers of carbon fiber wrap increases, the concrete restraint effect is enhanced, and its strength and strain increase accordingly. When the spacing of the carbon fiber wrap strips increases, the concrete restraint effect is weakened. Therefore, the number of layers and the spacing of the carbon fiber wrap should be set reasonably.

Carrying capacity performance of normal section of carbon fiber reinforced concrete columns

In the research and practice of carbon fiber-reinforced concrete columns, it is basically based on circumferentially wound carbon fiber wrap, and the compressive strength of the concrete column is improved by restraining the core concrete, thereby improving its ductility and deformation performance. However, experimental studies have shown that in terms of the bending resistance of the reinforced column, the effect of sticking carbon fiber wrap along the axis of the column is better than that of carbon fiber wrap in the circumferential direction. The main reason is that the tensile performance of the carbon fiber wrap is fully utilized. The performance is equivalent to the longitudinal tension steel bar, which is equivalent to adding the longitudinal tension steel bar of the concrete column. Experimental studies have shown that the reinforcement of carbon fiber wrap along the axis of the column can effectively improve the flexural bearing capacity of the column and prevent the development of cracks. Its effect is related to the number of fiber wrap layers. When the number of carbon fiber wrap layers increases, the reinforcement effect increases significantly, but when the number increases to a certain level, its influence on the improvement of bearing capacity gradually weakens. At the same time, the smaller the number of longitudinal tensile steel bars of the column, the more obvious the reinforcement effect. In particular, it should be emphasized that, in order to achieve a good reinforcement effect, so that the role of carbon fiber wrap can be effectively brought into play, the transverse carbon fiber tape should be pasted along the circumferential direction of the concrete column. To prevent the longitudinal carbon fiber wrap from slipping or end warping.

Mechanical properties of oblique section of carbon fiber reinforced concrete columns

Under the action of earthquake, the phenomenon of shear failure of concrete columns due to insufficient stirrups often occurs. For columns with insufficient stirrup reinforcement and shear failure, pasting carbon fiber wrap on the outside is a very effective reinforcement method. Its working mechanism is: when the carbon fiber wrap is wrapped around the circumference, the concrete is in a circumferential compression state, which becomes a confined concrete, and its compressive capacity and ductility are improved. The shear resistance is enhanced, and the role of carbon fiber wrap is equivalent to the stirrup in the concrete column. Experimental studies have shown that the ductility and shear capacity of concrete columns are improved to a large extent after carbon fiber sheets are used to reinforce concrete columns. The effect of this increase is related to the performance of the concrete columns and the number of layers of fiber sheets. When the number of layers of carbon fiber wrap increases, the concrete confinement effect will be enhanced, and its strength and ductility will be improved better. The increased shear capacity can transform the column from shear failure to bending failure, thereby effectively improving the ductility of the column. But when the number increases to a certain extent, its influence on the increase of shear capacity gradually weakens. At the same time, the larger the axial compression ratio of the concrete column, the better the ductility effect of the carbon fiber reinforced concrete column. Therefore, the amount of carbon fiber wrap should be set reasonably, and attention should be paid to the influence of the component's own performance on the reinforcing effect of carbon fiber wrap.

Seismic performance of carbon fiber reinforced concrete columns

Under the action of horizontal seismic force, the bending moment and shearing force at the end of the concrete column are relatively large. Carbon fiber wrap can be pasted along the axial and circumferential directions of the column at the same time to effectively improve its bending and shear resistance. So as to give full play to the ductility characteristics of the concrete column and improve its lateral force resistance. In order to improve the reinforcement effect, the upper and lower ends of the concrete column can be reinforced at the same time. When the lateral restraint of the upper end of the column is weak, only the reinforcement of the lower end of the concrete column can be considered. The main mechanism of the seismic performance of carbon fiber reinforced concrete columns is that after the concrete columns are wrapped with carbon fibers in the circumferential direction, the ultimate compressive strain value of the concrete is significantly increased. The crushing of the concrete in the compression zone is delayed, so that the plastic deformation performance of the steel bar can be fully exerted, thereby improving the ductility of the component. At the same time, compared with stirrups, the ring-wrapped carbon fiber wrap has a more direct and effective restraint on the concrete.

Experimental studies have shown that the ductility and hysteresis characteristics of the concrete column are significantly improved after the carbon fiber wrap is used to reinforce the concrete column, and the hysteresis loop becomes more and more full. At the same time, the reinforcement effect of the all-inclusive carbon fiber wrap of the concrete column is better than that of the strip fiber wrap. . Therefore, for seismic reinforcement, the all-inclusive carbon fiber wrap reinforcement method should be preferred to the strip reinforcement. At the same time, attention should be paid to the effect of the component's own performance on the carbon fiber wrap reinforcement effect.