Study On The Seismic Behavior Of Reinforced Concrete Columns Strengthened With TRC Under Conventional And Corrosion Environment

The textile reinforced concrete, a new fiber-reinforced cement-based composite,consisting of textile and fine grain concrete, has good bearing capacity, anti-crack capacity, and strain hardening properties. The fiber material of TRC has good resistance to corrosion and does not need additional concrete protective layer, so the geometry size and mass of the original structure are barely changed when it is used as repairing and reinforcing material. Further, fine grain concrete have good anti-permeability and resistance to freeze-thaw and carbonation, which helps to improve the durability of the structure. Based on these properties, TRC is widely used in strengthening RC structure gradually. This paper based the national natural science fund project “Degradation mechanism of seismic behavior of reinforced concrete columns strengthened with TRC in marine environment(51478458)” studied the seismic behavior of reinforced concrete columns strengthened with TRC.Firstly, an experimental study on the seismic behavior of reinforced concrete columns strengthened with TRC under conventional and corrosion environment was conducted. In the test, considering the influence of the textile layers and lap length of textile, stirrup ratio and axial compression ratio on TRC reinforcement effect, 11 RC columns were designed and made under conventional environment. Further, considering the influence of the corrosion rate and reinforcement order on TRC reinforcement effect,9 RC columns were designed and made under corrosion environment. Finally, according to test results, the restoring force model of reinforced concrete column strengthened with TRC was established. Specific results are summarized as follows:(1)TRC reinforcement could effectively constraint the core area of the concrete,restrict the development of concrete cracks, increase the initial stiffness of specimens,and improve the failure modes of RC columns. There was no significant effect of the number of layers on the yield load of the specimens. The peak load, displacement ductility coefficient and energy dissipation capacity were improved with the increase of the number of reinforcement layers when it consider 1 to 3 layers of textile reinforcement. However, the increase of the ductility was limited when the number of textile layer was increased continuously. There was no significant effect of the lap length of textile and stirrup ratio on bearing capacity of the specimens, but the displacement ductility coefficient and energy dissipation of columns strengthened with TRC were enhanced with the increase of lap length and stirrup ratio. In a small range of axial compression ratio, the cracking load, yield load, peak load and energyconsumption rate were improved with the increase of axial compression ratio.(2)TRC reinforcement could effectively inhibit the erosion of chloride ions on steel, reduce the corrosion rate of specimens, delay the development of cracks and stiffness degradation, and improve the overall failure modes of specimens under corrosion environment. The bearing capacity of TRC-strengthened columns may be little lower than unreinforced columns in small corrosion rate. The constraint efficiency of TRC-strengthened columns was improved with the increase of corrosion rate, but the displacement ductility coefficient decreases. Whether the reinforcement is before or after the corrosion, the seismic performance of specimens could be improved, and their initial stiffness of the two kinds of reinforcement order were the same. The bearing capacity of columns corroded after reinforced was lower than columns corroded before reinforced in some extent, but the stiffness degradation rate was slower than the latter.(3)Based on test results, the degradation three linear skeleton curve model was choose in this paper to establish skeleton curve model of reinforced concrete column strengthened with TRC, considering layers of textile and axial compression, and using the method of linear regression to calculate parameters of skeleton curve. The theoretical curves agreed well with the experimental curves. Based on skeleton curve model, the hysteresis rules were simplified and restoring force model of reinforced concrete column strengthened with TRC was established, and the theoretical curves agreed well with the experimental curves. This model has a certain accuracy and applicability, but it also need further study for a wider range of applications.