Research On Basic Mechanical Properties Of Micro-Expansive Lightweight Aggregate Rectangular CFST Stub Columns

Micro-expansive lightweight aggregate rectangular CFST is a kind of material with good performance on mechanical properties.Although bearing capacity of micro-expansive lightweight aggregate rectangular CFST is not as good as micro-expansive lightweight aggregate circular CFST,but it is simple and easy to process,so there is a certain application significance in actual project.In order to study the mechanical properties of micro-expansive lightweight aggregate concrete,this paper mainly deals with the following work:(1)The free deformation properties of micro-expansive lightweight aggregate concrete under different conditions of plastic wrap and natural conservation were studied.The results showed that:when the amount of expansive agent is less thanl2%,the expansion effect of the expansive agent increases with the increase of the expansive agent content,but the expansion effect decreases while the range is exceeded.(2)To study the effects of steel content,aspect ratio and expansion agent on the expansive properties of micro-expansive lightweight aggregate concrete,a total of 24 micro-expansive lightweight aggregate rectangular CFST short column specimens are set in this paper.The results showed that:the greater the steel content,the smaller the ring strain(tensile strain and compressive strain)of the outer wall of the pipe;the peak tensile strain at the initial stage of curing of the steel pipe with the expansion agent Of 12%is higher than that of the steel pipe with the expansion agent content of 16%;when the aspect ratio is 1,the circumferential strain of the four sides of the rectangular steel pipe is basically the same,and the strain of the short side of the rectangular steel pipe with an aspect ratio of 1.5 and 2 is slightly larger than that of the long side.(3)The axial compression test is carried out on the 24 micro-expansive lightweight aggregate rectangular CFST short columns,to study the effects of aspect ratio,expansive agent content and steel content on the axial compression behavior of micro-expansive lightweight aggregate CFST short columns.It can be known from the results that the higher the steelratio,the higher the ultimate bearing capacity of the short column specimens and the greater the ratio of the residual bearing capacity to the ultimate bearing capacity;the ultimate bearing capacity of the specimens with the expansive agent content of 12%is larger than that of the specimens with the expansive agent content of 16%;the increased coe fficient of bearing capacity of micro-expansive lightweight aggregate rectangular CFST short columns decrease with the increase of aspect ratio.(4)Several formulas for calculating the ultimate bearing capacity of rectangular concrete-filled steel tube are compared,it is found that the uniform theoretical calculation formula of Zhong Shantong is more suitable for calculating the axial ultimate bearing capacity of micro-expansive lightweight aggregate rectangular CFST short columns.In additional,the ANSYS finite element software was used to simulate the axial compression test of the micro-expansive lightweight aggregate rectangular CFST short columns,and the experimental results are in good agreement with the simulated results.