Experimental Investigation Of Rstrained Axial Compression Stainless Steel Columns At Elevated Temperatures

With the continuous progress and development of modern society, the construction industry has showed vigorous trend of development, more and more new materials and technology is being applied to the construction sector. People’s aesthetic requirements for the building is becoming higher and higher while they are in pursuit of its excellent function. As the crystal of the continuous development of new building materials, stainless steel has become more and more popular to the architect for its good appearance. It is because of its good characteristics, fire resistant paint is not needed in the actual project, and therefore the fire resistance performance of stainless steel worthy more attention.At the same time, the structure tends to have integrity under fire, and complex interactions occur in each member of the structure, and internal force redistribute. Study on reaction of single member can not rightly show the force characteristics of the structure ender fire.At present, little study has be done on force characteristics of stainless steel under high temperature in our country, and study on Stainless Steel Column with axial force is still blank. As the key component which take the force in the whole structure, the Column worthy more study of its fire resistance performance under fire, therefore it is of great importance for this thesis to study the fire resistance characteristics of Stainless Steel Column with axial force.Based on domestic austenitic stainless steel S30408, this thesis carried out the mechanical properties test of two normal temperature specimens and 14 high temperature steady-state specimens. The result showed that the two-stage R-O model parameters(hardening exponent n and coefficient m) which is proposed by Rasmussesn still need to be corrected, the modified two-stage R-O model can simulate the mechanical properties of stainless steel under high temperature better. The two-stage R-O stress-strain model proposed by Ju Chen can simulate the mechanical properties of stainless steel under high temperature,but its parameters in recommendation expression needs to be appropriate amended, and the modified two-stage R-O stress-strain model can simulate the mechanical properties of stainless steel under high temperature better.In order to investigate the performance of Stainless Steel Column with constraint axial force under fire, experiment has been carried out on fire resistance of 6 rectangular cross-section Stainless Steel Column with axial force. And the result showed the mechanical behavior and failure modes of Stainless Steel Column under fire, focusing on effects of load ratio, cross-sectional dimensions and restraint stiffness ratio parameters on Stainless Steel Column of its anti-fire properties. The test shows the oven temperature-time curve, the specimen surface temperature-time curve, axial deformation-time curve and specimen critical temperature of each test specimen, and reveals the damage mode of Stainless Steel Column with constaints axial force. The result showed that:load ratio n and axial direction resistance stiffness ratio have more obvious effects on fire resistance performance of rectangular cross-section Stainless Steel Column; for rectangular cross-section Stainless Steel Column of the same thickness, change on cross-sectional dimension will affect the failure mode of Stainless Steel Column specimen under fire. When the section of a Stainless Steel Column specimen meets the "European norms" forth category section, the test pieces take local buckling and bending buckling simultaneously during heating.ABAQUS, a finite element software is used to do the finite element numerical simulation analysis of each Stainless Steel Column specimen with constrain axial force in the anti-fire test, and the result verified the accuracy of the finite element model. And a parametric analysis is carried out on related factors which may have effect on the anti-fire performance of Stainless Steel Column specimen with constrain axial force, and the result showed that:axial restraint stiffness ratio β1, slenderness ratio λ and load ratio n are main factors that effect the anti-fire performance of Stainless Steel Column specimen with constrain axial force, the effect of initial imperfection eo is relatively small.Finally, refer to the fire resistance design method for unconstrained Stainless Steel Column mentioned in "European norms", force compressive process analysis is made on Stainless Steel Column specimen with constrain axial force under fire, with the effects of initial bend defect eo, axial restraint stiffness ratio β1, slenderness ratio λ, load ratio n and other factors taken into consideration, we deduced the axial force formula and buckling temperature formula of Stainless Steel Column specimen with constrain axial force, and verified the accuracy of this thesis on deriving formulas.