Research On The Design Of Molding And Axial Compression Performance Of Concrete Filled Steel Tube Short Column Modified From Square To Circle

In civil engineering, concrete filled steel tube structures are mainly used as compression members, which combining nature of both steel and concrete, and taking full advantages of each material of steel and concrete. Generally speaking, concrete filled steel tube structures have great bearing capacity, good ductility and toughness,better fire resistance, and good economic effect. Besides that, it is also simple and convenient for fabrication and construction.Therefore, these are lots of applications in high-rise and super high-rise buildings, bridges, large span structuresCurrently, the wideliest used forms of concrete filled steel tube structures are concrete filled circular steel tube member and concrete filled square steel tube member.Since both the concrete filled circular steel member and concrete filled square steel member have their own advantages, it is possible that these two different forms of concrete filled steel tube structures to be applied in the same project. Then there is the concrete filled steel tube short column modified from square to circle which connected both concrete filled circular steel column and concrete filled square steel column.In this thesis, combined with the concrete filled steel tube short column modified from square to circle appeared in the specific project, the main contents are listed as follows:(1) The pros and cons of manufacturing the concrete filled steel tube column modified from square to circle under the existing conditions was investigated. The autor put forward a new design model of oncrete filled steel tube column modified from square to circle. The model was analysed mathematically aiming at the difficulties in plane size and space position. The software was independently developed for calculating plane size and space position. And it was proved that the software can be used under conditions of any size and height.(2)A new manufacturing method for the concrete filled steel tube column modified from square to circle was put forward, which was already applied in a project with a good effect and a lot of cost savings.(3)For the research on the axial compression performance of concrete filled steel tube short column modified from square to circle, the concept of “equivalent cross-section” from the united theory of concrete filled steel tube was introduced. The axial compression performance of three groups of specimens(each group has a circleone,a square one and a one modified from square to circle) under the condition of equivalent cross-section was analyzed by the finite element software Ansys. The load displacement curves and the ultimate bearing capacity of the three groups of specimens was presented. The conclusion is that the axial compression performance of the concrete filled steel tube short column modified from square to circle is between concrete filled circular steel tube and concrete filled square steel tube, which verified the judgement of the unified theory of concrete filled steel tube that the behaviors of concrete-filled steel tubes members change with cross section,and the change exhibits continutity.