Dynamic Splitting Test And Analysis Of Fly Ash Concrete Filled Steel Tube

Fly ash concrete-filled steel tube is a kind of composite component filled with fly ash concrete in steel tube.It is a new structure which combines the advantages of fly ash concrete and steel tube.Fly ash concrete has good compressive capacity and steel pipe material has high tensile strength,which makes fly ash concrete members have high bearing capacity,good ductility and strong impact resistance.Because of its convenient processing and loading,it has been widely used in current civil engineering.Compared with concrete,the activity of fly ash will be reduced appropriately,which will inevitably affect the ultimate bearing capacity of components and reduce the safety of structures.At the same time,the research on mechanical properties of steel tube fly ash under dynamic loads is still in the exploratory stage,so it is very important to study the splitting performance of steel tube fly ash concrete members to ensure the safety of Engineering structures.In this paper,SHPB experimental system is used to carry out impact splitting test of concrete filled steel tubular fly ash.By changing the fly ash content and concrete grade,the influence of fly ash content on dynamic splitting performance of concrete filled steel tubular fly ash is studied.Specific research contents are as follows:(1)The basic principle and two hypotheses of SHPB experiment,one-dimensional hypothesis and stress uniformity hypothesis,are expounded,and two-wave and three-wave formulas are deduced on the basis of the hypothesis.(2)Static splitting tests of C30,C40 and C50 concrete were carried out to obtain their static tensile strength.At the same time,static splitting tests of concrete with different fly ash content were carried out to obtain the effect of fly ash parameters on the static tensile properties of concrete,which provided the necessary basis for the study of impact splitting properties of concrete filled with steel tube fly ash.(3)The impact splitting tests of concrete filled steel tube with fly ash under different impact velocities were carried out.According to SHPB test principle,the stress-strain curve,stress-time curve and strain-time curve of concrete filled steel tube under impact splitting are obtained.The results show that when the concrete strength is the same and the impact speed is the same,the more fly ash is added,the lower the dynamic ultimate strength is;when the impact speed and the fly ash content are the same,the higher the strength is,the better the deformation resistance is;when the fly ash content and the concrete strength are the same,the change of impact speed shows obvious strain rate effect.Therefore,the peak stress increases with the increase of impact velocity,and the damage degree of the specimen is related to the dynamic impact velocity,concrete strength and fly ash content.(4)The energy dissipation characteristics of concrete filled steel tube are studied,and the variation rules of incident energy,reflection energy,transmission energy and absorption energy in SHPB test are analyzed.It is found that the energy absorption coefficient decreases with the increase of fly ash content,and the strain rate effect is obvious under high-speed impact.Figure[41]table[11]reference[57]...