The Influence Of Shale Ceramsite Content On The Axial Compressive Behavior Of Concrete Filled Steel Tube Short Residence

In recent years,the improvement of the lightweight aggregate concrete has supplied a new direction for the development of the performance of concrete materials,and the ceramsite as a new type of lightweight aggregate has the characteristics of light weight and environmental protection.The addition of ceramsite reduced the weight of concrete filled steel tube,improved the material characteristics of core concrete,met the requirements of light weight,reduced the use of stone aggregate,and achieved the purpose of making full use of various building materials.In order to improve the use status of concrete and accelerate the use of ceramsite as concrete aggregate,shale ceramsite has been used as coarse aggregate to replace common coarse aggregate to form concrete filled steel tubular columns with ceramsite content,in order to carry out the experimental study on the axial compressive properties.The concrete filled steel tubular column with ceramsite content overcomed the brittleness of ceramsite,it not only saved the use of common coarse aggregate and ceramsite,but also exerted the hoop effect of steel tube on core concrete,and made concrete filled steel tubular column with ceramsite content form an organic whole.Five concrete filled steel tubular columns with ceramsite content and one ordinary concrete filled steel tubular column were fabricated,and the axial compressive properties of the concrete filled steel tubular columns with ceramsite content and steel tube wall thickness were studied.Based on the experimental phenomena,bearing capacity of members,loaddisplacement curves of members and load-strain curves of steel tubes,and combined with the experimental parameters,numerical analysis carried out by finite element software.The main conclusions gained in the final were as follows:(1)The wall thickness of steel tube was 2 mm,the self-weight of concrete filled steel tubular members with different ceramsite content decreased gradually with the increase of ceramsite content.The content of ceramsite increased from 0% to 20%,the weight of ceramsite decreased by 5.33%,the content of ceramsite increased from 0% to 40%,the weight of ceramsite decreased by 9.41%,the content of ceramsite increased from 0% to 60%,and the weight of ceramsite decreased by 14.03%.(2)Combined with the experimental data and numerical analysis results,the ultimate bearing capacity of the steel tube decreased with the increase of ceramsite content as the wall thickness of the steel tube remained unchanged.When the wall thickness of steel tube was 2 mm,the content of ceramsite increased from 0% to 20%,the ultimate bearing capacity decreased by 2.35%,the content of ceramsite increased from 0% to 40%,the ultimate bearing capacity decreased by 7.24%,the content of ceramsite increased from 0% to 60%,and the ultimate bearing capacity decreased by 9.40%.(3)Combined with the experimental data and numerical analysis results,the ultimate bearing capacity of the component increased linearly with the increase of the wall thickness of the steel tube with the constant content of ceramsite.When the content of ceramsite was 40%,the wall thickness of steel tube increased from 1 mm to 2 mm,and its ultimate bearing capacity increased by 43.75%;when the wall thickness of steel tube increased from 1 mm to 3 mm,its ultimate bearing capacity increased by 105.36%;when the wall thickness of steel tube increased from 1 mm to 4 mm,its ultimate bearing capacity increased by 142.86%;when the wall thickness of steel tube increased from 1 mm to 5 mm,its ultimate bearing capacity increased by 189.64%;(4)Based on the test and numerical analysis data and the corresponding dead weight and ultimate bearing capacity of each component,the effect of ceramsite content of 20% on the dead weight and ultimate bearing capacity of concrete filled steel tubular members was relatively small.The dead weight of the component with ceramsite content of 20% was 95.46% of the component with ceramsite content of 0%,while the corresponding average ultimate bearing capacity reached 99.21%.It can be seen that the component with 20% ceramsite content has similar mechanical properties to that of ordinary concrete filled steel tubular members.The optimum volume fraction of ceramsite in this paper is suitable for production practice.(5)On the basis of comparative analysis of domestic and foreign codes and regulations,this paper considerd the revision of AIJ(1997)formula based on Japanese code to applying the calculation of ultimate bearing capacity of concrete filled steel tubular columns in this test.