Specimen C7

Specimen C7 was severely corroded before the reinforcement。 More vertical corrosion cracks appeared, with widths up to 0。4 mm。 Some of the concrete spalled significantly in the chiseling, and the color of the concrete turned black。 The test results showed that the electric corrosion caused a certain degree of damage to Specimen C7。 When the horizontal force reached 76 kN, the first horizontal crack appeared with a 0。06 mm width。 When the horizontal force was 84 kN, the steel bar yielded, diagonal cracks appeared in the column, and a few vertical cracks appeared at a right angle to the column root。 In the first loop of the 3Δy loading, the horizontal load reached its peak value, which was equivalent to that of Speci- men C1。 In the 5Δy loading, the horizontal bearing capacity fell below 85% of the peak load, and the textile fractured at a right angle to the column root。 The final failure of Specimen C7 was basically the same as that of Specimen C6。 The longitudinal rein- forcements were chiseled out after the test, and the measured cor- rosion ratio of the steel was  13。82%。

Failure Mode

The failure modes of the specimens are shown in Fig。 6。 The failure of the specimens was a typical bending failure。 The main conclu- sions from the failure mode are as  follows:

• TRC reinforcement can effectively reduce the effect of chloride ions on the corrosion of steel。 Compared with the unstrength- ened Specimen C1, Specimen C2, which was strengthened with two layers prior to the corrosion, and Specimen C3, which was strengthened after the corrosion, exhibited desirable character- istics of slow crack development, a small quantity of cracks, a thin seam width, and a strong overall seismic deformation ca- pacity after exposure to a 5% corrosion environment;   and 来*自-优=尔,论:文+网www.youerw.com

• Compared with the unstrengthened columns, the failure mode of the columns strengthened with TRC exhibited a significant im- provement in crack development and deformation capacity un- der the condition of a high corrosion ratio (more than 5%), and the strengthened columns exhibited a better seismic perfor- mance。 The mechanical properties of Specimen C7 showed a certain degree of damage because of the higher corrosion  ratio

Fig。 6。 Failure mode of specimen: (a) Specimen C1; (b) Specimen C2; (c) Specimen C3; (d) Specimen C4; (e) Specimen C5; (f) Specimen C6;

(g) Specimen C7

(13。82%) before reinforcement, but it still demonstrated a suffi- ciently high bearing capacity and a certain deformation capacity after reinforcement, and the failure mode was still bending failure。

Hysteresis Curve

The main experimental results are given in Table 5, and the mea- sured corrosion ratios of the steel are provided in Table 6。 The position of the yield point was determined by the Park method (Park and Paulay 1975), the peak load is the maximum horizontal load of the whole loading process, the ultimate load is equal to the load when the horizontal bearing capacity falls below 85% of the peak load or when the specimen fails, the displacement ductility factor is the ratio between the ultimate displacement and the yield displacement, and the cumulative energy dissipation is the enclosed area of the hysteresis loop in the load-displacement curve。 The hys- teresis curves of the specimens are shown in Fig。   7。

Fig。 7 shows that the load and displacement of the specimens are basically linear in the prime period of loading。 There is hardly any  residual  deformation  after  unloading  in  the  elastic   stage。

In the elastic plastic stage, there is a hysteresis loop。 This means that residual deformation appeared, the slope of the load curve de- creased with the increase in the load, and the stiffness degeneration was relatively obvious。