Research On The Axial Ultimate Bearing Capacity And Impact Resistant Behavior Of Concrete-filled Stiffened Steel Square Tubular Short Column

The concrete-filled stiffened steel square tube is an innovation in the form of Steel structure and concrete filled steel tube structure. It is a new type of composite structure which put the stiffening ribs into the tube before pouring concrete. It is getting more and more attention cause it have a lot of advantages such as have a better bending stiffness, simple connection node, easy to build, have a better restraints to the core concrete, et. However, the research on concrete-filled stiffened steel square tubular column is not complete enough today. Most of the researcher gets the ultimate bearing capacity by test or finite element analysis, rare theoretical analysis; researches on mechanical properties under impact loading are mostly for the circular section concrete-filled steel tube, rare square section ones. Therefore, it has a very important significance to study this new type of composite structure further. In this paper, theoretical method and numerical simulation will be used, the primary work and innovations are as follows:(1) Based on the unified strength theory, by introduce into the uniform restraint coefficient and stiffener stiffness, the performance of square section was analyzed by converted to circular cross section, then considering the useful effect of the PBL shear connectors, formulas for calculating the ultimate bearing capacity were deduced. Verified the correctness by comparison with literature test results, the influencing factors of formula such as parameter b, the concrete friction angle and the width and thickness of the rib were also discussed.(2) The ultimate axial compression bearing capacity on concrete-filled steel square tubular short column stiffened with ribs and concrete-filled steel square tubular short column stiffened with PBL were analyzed by using the commercial finite element software ANSYS. On the assumption that there is no relative slippage among concrete and steel tube, the ultimate bearing capacities were simulated.Compared with the test results and the formula in this paper, they coincided well with each other, which verified the correctness of the model, then discussed the stress state of the column and the major influencing factors.(3) Use the finite element analysis software ANSYS/LS-DYNA to establish the model under impact loading. By comparison with the corresponding literature test to verify the correctness of the model, the failure modes under impact loading, impact energy time curve and maximum deformation were also analyzed. Then discussed the main parameters affecting of the column under impact loading such as material properties, rib size, quality of the hammer and Impact position.