However, there have been few studies of the seismic behavior of TRC-reinforced RC columns under an erosion environment。 Azad and Al-Osta (2014) tested 48 specimens under eccentric axial load- ing and developed a strength-prediction model on the basis of a substantial amount of test data。 Bousias et al。 (2004) concluded that although wrapping with FRP is found to significantly improve the seismic performance of columns that suffer from both a lack of seismic detailing and the corrosion of the reinforcement, such cor- rosion materially reduces the effectiveness of the FRP wrap as a strengthening measure, as the corroded bars become the weak link of the column, instead of the confined compression zone。 Accord- ing to Li et al。 (2009), strengthening corroded RC columns with combined CFRP sheets and steel jacket was effective in enhancing the seismic performance of the columns and resulted in more-stable

structures in structural seismic design, and the interaction between an earthquake and corrosion remains for further study。 Akiyama and Frangopol (2014) noted that although an accurate model for the analysis of flexural and shear  effects  has  been established, the effect of corrosion on the seismic performance life assessment has been almost neglected。 Therefore, this paper conducted exper- imental research on the seismic performance of reinforced concrete columns strengthened by TRC under low cyclic loading with envi- ronmental corrosion and analyzed the seismic performance param- eters, including the failure mode of the columns, hysteretic curve, skeleton curve, ductility, and energy-dissipation capacity。 Then, the effects of the corrosion ratio and different reinforcement methods on the seismic performance were investigated。

Experimental Program

Specimen Design

In this investigation, a total of seven reinforced concrete square col- umn specimens designated C1–C7 were designed and fabricated。 Two of them were used as control columns; two of them were first strengthened with TRC after the surface of the concrete was chis- eled and were then corroded; and the remaining three were first corroded, and then TRC was used to strengthen the corrosion- damaged specimens, as indicated in Table 1。 The cross-sectional dimensions were 300 × 300 mm, and the total height of all the col- umns was 1,740 mm, with a 3。8 shear-span ratio。 Six C14 steel bars were used as the longitudinal reinforcement, and smooth steel bars with a diameter of 8 mm were used as the stirrups, with 100-mm spacing to meet the building code requirements for structural concrete and commentary [ACI 318-11 (ACI 2011)]。 Stirrup densification was taken in the range of 100 mm from the root of the columns with 50-mm spacing。 The specific size and reinforce- ment of the specimens are shown in Fig。 1。 The concrete class was C40。

Strengthening Method

The strengthening procedure was first to chisel the surface of the concrete-confined specimen having a reinforcement  height  of 600 mm from the root, and the corners of the columns were rounded。 The specimens were wetted before strengthening and coated with fine-grain concrete at  a  2–3  mm  thickness。 Then, the textile was tiled on a template, and mortar was brushed over the textile, which was wrapped on the column reinforcement area。

Table 1。 Basic Parameters of the Test Specimen Theoretical

hysteresis  curves with lower  strength  degradations as  compared

with the unstrengthened ones。 Ma et al。 (2012) pointed that higher corrosion levels and higher axial loads result in less-stable hyster-

Serial number

Concrete strength

corrosion

ratio (%) Strengthening manners

etic loops with more-severe strength and stiffness degradations and worse ductility。 Inci et al。 (2013) concluded that the main negative effect of corrosion on the strength is the reduction in the diameter of the rebar, whereas its negative effect on the displacement capacity comes from the concentration of plastic steel strains at the sections of reinforcing bars at which the corrosion-induced pits are at a maximum。 Further, Biondini et al。 (2014) presented that the strength and the ductility of the structures change with time and then the failure mechanism forms, which affects the seismic per- formance of the structures。 Hence, it is necessary to account for both the environmental severity and overall performance of the