Study On Dynamic Mechanical Properties Of Concrete-filled FRP Tubes Composite Structure

FRP materials have attracted the attention of domestic and foreign researchers because of their strong corrosion resistance and high specific strength.Concrete-filled FRP tubes structure is formed by pouring concrete into prefabricated FRP tube.FRP tube outside the structure provides restraint function for core concrete to improve its strength and ductility;FRP plays a protective role in concrete and enhances its corrosion resistance,and the presence of inner concrete can delay the buckling of FRP tube thin-walled members;FRP tube can be used as formwork during pouring.Many experiments have been carried out on the static mechanics and dynamic compression properties of concrete-filled FRP tube,and the conclusion that FRP tube binding can improve the concrete performance obviously is obtained.However,there are few researches on the dynamic splitting and tensile properties of FRP tube confined concrete.In this paper,the dynamic splitting tensile test of concrete-filled FRP tube samples was carried out by SHPB device.The effects of strain rates(33.0 s-1,37.1s-1,42.8 s-1,48.6 s-1),FRP tube wall thickness(2 mm,3 mm,4 mm,5 mm),core concrete strength(C30,C40)on the dynamic mechanical properties and energy dissipation were studied.The results and conclusions are as follows:(1)The peak stress and peak strain increase with the increase of strain rate,which has obvious strain rate effect.With the increase of the wall thickness of the FRP tube,the rising speed of the peak stress with the strain rate decreases obviously,and the sensitivity of the dynamic peak stress to the strain rate decreases with the increase of the wall thickness of the FRP tube.(2)Under the same dynamic loading,with a certain wall thickness,the higher the strength grade of core concrete,the greater the peak stress of concrete-filled FRP tube and the stronger the ability to resist failure.The strength of core concrete has little influence on the time when the specimen reaches the peak stress.At the same strain rate,the peak stress of C40 core concrete is higher than that of C30 core concrete.(3)Under the strain rate of 33.0 s-1～48.6 s-1,the concrete-filled FRP tube can maintain good integrity.The failure mode conforms to the splitting criterion,and the specimen splits along the radial direction.With the increase of strain rate,the damage degree of concrete-filled FRP tube becomes more and more serious.When the failure degree of the specimen is relatively high,it can be seen that the failure degree of the incident end of concrete-filled FRP tube is greater than that of the transmission end.(4)The incident energy and reflected energy of concrete-filled FRP tube samples are linearly correlated with the strain rate,and the absorbed energy increases with the strain rate.Compared with other energies,the transmission energy is very small.With the increase of the wall thickness of concrete-filled FRP tube,the reflected energy decreases with the increase of strain rate.When the strength of core concrete is C30 and the incident energy is constant,the reflected energy is always greater than the absorbed energy,and the growth rate is greater than that of the absorbed energy.(5)There is a good linear relationship between the energy dissipation density and the incident energy.When the incident energy is low,the crushing energy density of concrete-filled FRP tube with small wall thickness is small.Compared with the specimen with C40 core concrete strength,the crushing energy consumption density of C30 core concrete strength is obviously lower.Figure[38]Table[11]Reference[103]...