Study on Axial Compressive Capacity of FRP-Confined Concrete-Filled Steel Tubes and Its Comparisons with Other Composite Structural Systems

Jun Deng,Yi Wang,Tonghua Liu,Yifeng Zheng,Hui Li

doi:10.1155/2017/6272754

Abstract

Concrete-filled steel tubular (CFST) columns have been widely used for constructions in recent decades because of their high axial strength. In CFSTs, however, steel tubes are susceptible to degradation due to corrosion, which results in the decrease of axial strength of CFSTs. To further improve the axial strength of CFST columns, carbon fiber reinforced polymer (CFRP) sheets and basalt fiber reinforced polymer (BFRP) sheets are applied to warp the CFSTs. This paper presents an experimental study on the axial compressive capacity of CFRP-confined CFSTs and BFRP-confined CFSTs, which verified the analytical model with considering the effect of concrete self-stressing. CFSTs wrapped with FRP exhibited a higher ductile behavior. Wrapping with CFRP and BFRP improves the axial compressive capacity of CFSTs by 61.4% and 17.7%, respectively. Compared with the previous composite structural systems of concrete-filled FRP tubes (CFFTs) and double-skin tubular columns (DSTCs), FRP-confined CFSTs were convenient in reinforcing existing structures because of softness of the FRP sheets. Moreover, axial compressive capacity of CFSTs wrapped with CFRP sheets was higher than CFFTs and DSTCs, while the compressive strength of DSTCs was higher than the retrofitted CFSTs.

Highlights

In a conventional concrete-filled steel tubular (CFST) column system, concrete was filled in steel tubes, which typically continued throughout several stories or the full-height of a building [1, 2]
The four types of columns have their own advantages: (a) concrete-filled FRP tubes (CFFTs) do not need steel and double-skin tubular columns (DSTCs)-H can cost less concrete; (b) DSTC-H is lighter than CFSTs wrapped with CFRP sheets (CCFSTs) and CFFT; (c) CFFT, DSTC-H, and DSTC-F are used as new structures, while CCFST is generally applied to reinforce existing structures; (d) as the novel structures, CFFT and DSTC are applied by well-shaped columns in present; (e) CCFST is conveniently utilized in the structures of the steel tube columns reinforced in active service, which benefits from softness of the FRP sheets
This paper investigated the axial compressive capacity and strength of FRP strengthened CFST (FCFST)

Summary

Introduction

In a conventional concrete-filled steel tubular (CFST) column system, concrete was filled in steel tubes, which typically continued throughout several stories or the full-height of a building [1, 2]. In CFSTs, steel tubes are susceptible to degradation due to corrosion, which results in the reducing of axial strength of CFSTs. To overcome the disadvantages, Xiao [3] proposed the FRP strengthened CFST (FCFST) columns. Thereafter, many studies were conducted by Xiao et al [4,5,6] and other researchers [5, 7,8,9,10,11] on the effectiveness of FRP wrapping in improving the structural behavior of CFST columns. Ozbakkaloglu et al [20,21,22] conducted studies on the axial compressive behavior of concretefilled FRP tubes (CFFTs) and double-skin tubular columns (DSTCs). Our test results were compared with existing test results of CFFT, DSTC-H, and DSTC-F

Analytical Study

Experimental Study

Experimental Results and Discussions

Conclusions