Axial Compressive Behaviors Of Rectangular Concrete-filled FRP Tube And Rectangular FRP-concrete-steel Double-skin Tubular Stud Columns

FRP confined concrete column and FRP-concrete-steel double-skin tubular have excellent corrosion resistance and anti-seismic performance.FRP fiber material can improve structutal durability,prolong design life,reduce structure maintenance cost,internal steel tube makes construction convenient and low construction cost.Up to now,the research on circular FRP confined concrete columns is relatively perfect,but the rectangular FRP confined concrete columns are not enough,especially for different kinds of FRP confined rectangular concrete columns.The research on FRP-concrete-steel double-skin tubular is in the primary stage,and the existing research is concentrated on circular steel tubes with circular FRP tubes.And a small number of composite columns with circle steel tubes and square FRP tubes,and there is none research on rectangular FRP-concrete-filled steel tubular columns.On the basis of the existing research,this paper carries out an experimental study on rectangular FRP confined concrete column and rectangular FRP-concrete-steel double-skin tubular,The specific work is as follows:(1).A total of 54 columns was tested under monotonic axial compression,including 8 rectangular CFRP confined concrete column,16 rectangular GFRP confined concrete column,4 rectangular PET confined concrete column,8 rectangular GFRP confined hollow concrete column and 18 rectangular FRP-concrete-steel double-skin tubular.(2).The difference of the failure modes was investigated.how the aspect ratio,the type of FRP,the thick of FRP,void ratio affected the load capacity,the ductility,and the behavior of the concrete.the research showed that: ultimate stress decrease and ultimate strain increase with the aspect ratio ascend in rectangular confined concrete column,but ultimate stress increase with the aspect ratio ascend in rectangular FRP-concrete-steel double-skin tubular;The lateral rupture strain of CFRP and GFRP is similar,even if the material tensile strain of GFRP much bigger.The thicker FRP,ultimate stress and ultimate strain get bigger;The void ratio had little influence on ultimate stress,ultimate strain get bigger with the void ratio increase.(3).Based on the design-oriented stress-strain model for FRP-confined concrete proposed by Prof.Teng et al,two new design-oriented stress-strain model was proposed suitable for rectangular FRP confined concrete column and rectangular FRP-concrete-steel double-skin tubular,compared with others' models,the new model has a good performance.