Abstract
Fiber-reinforced polymer (FRP) has been widely used in civil engineering due to its light weight, high strength, convenient construction, and strong corrosion resistance. One of the important applications of FRP composites is the concrete-filled FRP tube (CFFT), which can greatly improve the compressive strength and ductility of concrete as well as facilitate construction. In this article, the compressive performances of a normal concrete-filled FRP tube (N-CFFT) column with 5-hour curing time and an ultra-early strength concrete-filled FRP tube (UES–CFFT) column with zero curing time were studied by considering the characteristics of rapid early strength improvement of ultra-early strength concrete and the confinement effect of the FRP tube. Monotonic axial compression tests were carried out on 3 empty FRP tubes (FTs) without an internal filler and 6 CFFT (3 N-CFFTs and 3 UES-CFFTs) specimens. All specimens were cylinders of 200 mm in diameter and 600 mm in height, confined by glass fiber–reinforced polymer (GFRP). Test results indicated that the compressive bearing capacity of the specimens increased significantly by adopting the ultra-early strength concrete as the core concrete of the CFFT, although the curing time was zero. It was also shown that the compressive behavior of the UES–CFFT specimens with zero curing time increased significantly than that of the N-CFFT specimens with 5-hour curing time because the former was able to achieve rapid strength enhancement in a very short time than the latter. The ultimate compressive strength of UES–CFFT specimens with zero curing time reached 78.3 MPa, which was 66.2 and 97.2% higher than that of N-CFFT with 5-hour curing time and FT specimens, respectively. In addition, a simple confinement model to predict the strength of UES–CFFT with zero curing time in ultimate condition was introduced. Compared with the existing models, the proposed model could predict the ultimate strength of UES–CFFT specimens with zero curing time with better accuracy.
Highlights
The application of fiber-reinforced polymer (FRP) composites for strengthening and rehabilitation of concrete structures is gaining increasing popularity in the civil engineering community
When the FRP tubes (FTs) specimen was loaded (Figure 4A), as the load increased, the transverse tensile stress of the Fiber-reinforced polymer (FRP) tube increased and cracks began to appear in the middle upper part of the FRP tube
The development trend of the cracks was not the overall cracking around the FRP tube, but the slight cracks appeared at some positions and gradually extended along the circumferential direction to both sides
Summary
The application of fiber-reinforced polymer (FRP) composites for strengthening and rehabilitation of concrete structures is gaining increasing popularity in the civil engineering community. The concrete-filled FRP tubes (CFFTs) can be used as compression members such as piers, piles, and towers of bridges. Mirmiran et al (Mirmiran and Shahawy, 1997; 1998; Mirmiran et al, 2001) conducted experimental studies on the axial compression performance of the CFFT specimens and discussed the influence of significant factors (e.g., column section shape, FRP tube thickness, concrete strength, slenderness ratio, and other parameters) on the axial compression performance. The three materials worked together, maximizing the strengths, and avoiding the weaknesses, so that the FRP tube composite column generated many excellent mechanical properties. Zhuo and Fan (Zhuo and Fan, 2005) studied the seismic performance of FRP tube concrete bridge piers through pseudo-static and shaking table tests. The results showed that FRP tube concrete bridge piers had good seismic performance and could overcome the seismic vulnerability defects of normal reinforced concrete bridge piers
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