Experimental Study On The Mechanical Properties Of FRP Reinforcement Corroded Reinforced Concrete Column And Corroded Steel Bar Buckling Characteristics

Steel bar corrosion is an important cause for early failure of the safety, applicability, durability and structure. Reinforcement of corroded reinforced concrete structures is an effective method for improving service life of structures. Fiber reinforced polymer(FRP) has the advantages of light weight, high strength, corrosion resistance, good fatigue resistance, good stability and convenient for construction, etc., therefore, it is the first choice for the reinforcement of corroded reinforced concrete structure. This project systematically studies the mechanical properties of FRP reinforcement corroded reinforced concrete column and the influencing mechanism of FRP reinforcement on the mechanical properties of corroded steel bar buckling. The main research contents include the following aspects:1) Carry out mechanical properties study on steel bars in two states, uniform corrosion and pitting corrosion. Through rational design to accelerate corrosion test, obtaining two kinds of steel specimens which are uniformly corroded and pitting corroded. Conduct buckling test on the two types of corroded steel specimens, and obtain the buckling modes and the stress-strain relationship of both types of steel bars; the test result shows that the buckling modes of uniformly corroded steel specimens and no corrosion steel specimens are the same; and for pitting corrosion steel specimens, as pitting corrosion points close to the center of specimens, buckling is more likely to occur in the pitting corrosion positions. Conduct tensile tests on the two types of steel bars to obtain the tensile fracture morphology and stress-strain relationship of two types of corroded steel bars, and the test result shows that tensile rupture of steel bars all occur in the interface with serious corrosion or pitting corrosion positions. If corroded damage occurred to steel bar, the performance will decline, and the mechanical properties of steel bars will decline with the increase of corrosion.2) Experimental study on the mechanical properties of FRP reinforcement corroded reinforced concrete columns are conducted. Through accelerated corrosion test to obtain the uniform corrosion and pitting corrosion reinforced concrete columns with different corrosion degrees, and conduct axial compression test on the corroded reinforced concrete columns. Obtain the P-△ curve and stress-strain curves of FRP reinforcement corroded reinforced concrete columns; analyze the energy dissipation characteristics of reinforced concrete columns. After the concrete column being FRP reinforced, its mechanical properties, ductility and energy dissipation properties are greatly improved.3) Based on the axial compression test result of FRP reinforcement corroded reinforced concrete columns, this paper analyzes the interaction of FRP circumferential constraints and corroded steel buckling; and it reveals the influencing mechanism of pitting positions, corrosion rate, steel slenderness ratio and constraint stiffness on the buckling characteristics of corroded steel bar. In RC column, the actual corrosion rate(cross-section loss rate) of pitting corrosion is small, and under the constraint of surrounding concrete, pitting positions have little effect on the bearing capacity of RC column; the bearing capacity of uniform corrosion RC column decreases with the increase of steel corrosion rate(quality loss rate), and in the same corrosion rate, the bigger the reinforcement ratio per unit volume is, the obvious the deterioration of RC column properties is; when FRP constraint stiffness increases, the buckling deformation and bearing capacity of corrosion RC column are obviously improved.