248 / 2022-06-15 23:46:05

Creep behavior of hybrid FRP-concrete-steel double-skin tubular columns under sustained loading

FRP,Concrete-filled FRP tube,GFRP tube,creep,long-term evaluation

Hybrid FRP-concrete-steel double-skin tubular member (FCS DSTM) is a new type of composite structural member consisting of outer FRP tube, inner steel tube and concrete filled in between. The DSTM is featured by a number of salient characteristics, such high load-carrying capacity, easy construction and excellent corrosion resistance. Although the short-term behavior of DSTMs has been extensively investigated and based on which design/analysis methods have been developed, their long-term behavior, especially the creep behavior under sustained loading, has not yet been studied by the research community. In recent years, the authors’ research group has successfully implemented the application of DSTMs in bridge piers, bridge girders and arch bridges. Under this background, the research into the long-term behavior of DSTMs has become an urgent need in terms of both research significance and engineering applications. This lecture introduces a recent study carried out on the creep behavior of the FCS double-skin tubular columns (FCS DSTCs) under sustained loading. Effects of a number of parameters, including concrete type (normal concrete and self-compacting concrete), loading time, thickness of GFRP tubes and steel tubes, loading methods, as well as shear studs and internal steel reinforcements, have been investigated.



The test results showed that compared with plain concrete column and concrete-filled FRP tubes (CFFT), the creep strain of DSTCs is appreciably smaller. It was found that the creep coefficient is much less than1.0 for most of the specimens when the axial compression ratio is between 0.3 to 0.4. It was also found that deployment of shear studs and/or internal steel reinforcements has a favorable effect on reducing the creep strain. The DSTCs, after being subjected to sustained loading for about 230 days, were then tested under axial compression load, and it was found that the compression behavior, including failure mode, load-carrying capacity and deformation capacity, as well as the initial axial stiffness and GFRP cracking load, remains nearly unchanged. The test results suggest that when the axial compression ratio is low (0.3-0.4), the effects of creep on the compressive behavior of DSTCs are marginal.