Study On Mechanical Performance And Emperature Field Of Concrete Filled Steel Tubular Short Columns Under Axial Compression

The concrete filled steel tubular structure has many excellent properties, such as higher load bearing, better plasticity and toughness, faster construction progress as well as its apparent economic profitability. It has been widely applied to high-rise buildings, industrial workshop, arch bridges, underground and other structural project. Great attention has been paid to its mechanical performance and design theory by the academe around the world. Design Code has been maken but it's not perfect. Formula of limit bearing capacity is based on any hypothesis and isn't close to the actual bearing situation, it lack full consideration of the interfacial bond slip and friction coefficient. The main contents are as follows:1. Taken concrete filled steel tubular short columns as research object, the linear Mohr-coulomb criterion is applied to core concrete, the formula for calculating the limit bearing capacity of concrete filled steel tubular short columns under axial compression is obtained and verified by the tests available in literatures, it is proved that it is an easy method for calculating the limit bearing capacity of concrete filled steel tubular short columns.2. Finite element analysis models are set up for pure concrete tubular columns under axial compression, the connection between confining pressure and concrete tubular columns limit bearing capacity has been gained, then comparing with the results of the three-direction presser theory of concrete of the linear Mohr-coulomb criterion, and it validate the concrete models are accurate.3. Finite element analysis models are set up for concrete filled steel tubular short columns under axial compression using the finite element program ADINA, first in the model the interfacial bond slip is not considered, where nodes between the interface of the two materials coupling directly; then considering the interfacial bond slip, contact cell is defined on the contact surface, also the friction coefficient. The results make clear that: the concrete filled steel tubular structure of considering the interfacial bond slip can describe its actual force estate, magnitude of friction coefficient and shearing strength of concrete have small effect on the structure. Finally the distributing of stress, strain and distortion are analyzed. The influence of the steel thickness and the grade of concrete on the stress,strain and distortion are also discussed.4. Finite element analysis models are set up for calculating concrete filled steel tubular columns after high temperatures using the numerical analysis method. The temperature field distribution of concrete filled steel tubular columns after high temperatures is simulated and the main law of temperature field distribution is found. Temperature field analysis makes it possible to study further the mechanical performance and the fire resistance of concrete filled steel tubular structure.