Study On Mechanical Properties Of High Strength Concrete Filled High Strength Steel Tube Columns With Reinforced Cage Under Biaxial Bias

Under the leadership of the Party,the country is rich and strong,the nation is rejuvenated,and China’s urbanization construction is constantly advancing.It has made many achievements and accumulated rich experience in the field of civil engineering.With the improvement of construction technology,the research and development of new materials and the renewal of corresponding facilities and equipment,people continue to have new demand for future buildings.How to reduce economic expenditure and resource consumption as much as possible and increase the beauty and comfort of buildings and structures have become the most concerned issues for all civil engineers on the premise of ensuring quality and safety.High-strength concrete filled steel tube composite columns use two kinds of high-strength materials.On the one hand,the use of high-strength concrete can reduce the amount of concrete and promote the development of green environmental protection.On the other hand,the use of high-strength steel tube can improve the brittleness of high-strength concrete and avoid the inward buckling of steel tube.Therefore,the use of high-strength materials in concrete-filled steel tubular structures should become the focus of research and the future trend.However,due to the relative lag of the production of building structural steel in our country,there are obvious deficiencies in the research and application of high-strength steel in our country.In summary,the theoretical research and practical application of concrete-filled steel tubular composite columns with double highstrength materials should be strengthened.With the increase of the strength of high-strength concrete,the brittle failure becomes more obvious,and there is a weak constraint zone in the middle of the square steel tube,which leads to the failure of the specimen,the performance of the material can not be brought into full play.Related studies clearly put forward that built-in reinforcement can further strengthen the constraint of steel pipe on concrete,but the construction method of welding reinforcement will lead to construction difficulties and not easy to popularize.In order to improve the construction efficiency and reduce the construction difficulty,the concrete-filled steel tube column with built-in reinforcement cage is proposed in this paper.Combined with the three methods of mechanical test,finite element analysis and calculation formula,the axial loading and eccentric loading of high-strength square steel tube high-strength concrete medium-long columns with built-in reinforcement cage are studied.The main results are as follows:(1)21 medium-long column specimens are tested and studied,and the parameters include load eccentricity,slenderness ratio,section width-thickness ratio,concrete compressive strength and internal reinforcement cage form.Through the mechanical test,the apparent drum state of the specimen is obtained,the relevant curves are drawn,and the ultimate bearing capacity,initial stiffness,ductility and other mechanical properties of the specimen are deeply analyzed and discussed.(2)the corresponding analysis model is established by selecting the simulation software ABAQUS,and the rationality and accuracy of the analysis model are determined.On this basis,combined with Mises stress,longitudinal stress,plastic strain and contact stress and other means,more in-depth analysis of the role of each part of the member in the whole process of stress and mechanical characteristics,thus further elaborated the stress process and mechanism of this kind of specimen.(3)A large number of parameter analyses are carried out,and the effects of different parameters on the stiffness and bearing capacity of the specimen are calculated.based on the law of the simulation results,the design details and suggestions of concrete-filled steel tubular members with built-in reinforcement cage are given.(4)by comparing the test data with the calculation methods of the code and related literature,the formula for calculating the axial bearing capacity of concrete-filled steel tubular medium-long columns with built-in steel cages is perfected.Combined with the previous improved Pmurm curve,the improved curve is extended to the reinforced cage concrete-filled square steel tubular column in this paper.the difference between the calculated value of the formula and the measured value of the test is basically less than10%,which is recommended.