Study On Fire Resistance Of Restrained High Strength Q460Steel Column

Now, the fire resistance design is changing from test-based design method tocalculation-based design method. Many countries have issued structural fire designcodes. These structural fire design codes assured the fire safety of structures bycalculating isolated members. But, building structure has integrity and continuity, andthe members will produce complex interactions and internal stress redistribution. Inorder to reflect the real force of members, many researchers established sub-framemodel to investigate the performance of single member in fire. The theory andnumerical analysis considered the restraint effect supplied by other members. Thestudies of restrained members in fire provided theoretical basis and design guidance forengineering practice. With the widely being used of high strength Q460steel inbuildings, the behaviour of Q460steel in fire called for the people’s attention. Steelcolumn is the main component in steel frame structure. Therefore, it is very interestingand important to study the fire-resistance of high strength Q460steel column. Eightsubstructures experiments were carried out to study the performance of restrained highstrength Q460steel column in fire based on previous test and theory. And then, a finiteelement model was established to analyse the test specimens in this paper. The mainwork in this paper includes the following parts:（1）Material properties：The material properties of Q460C steel plate before andpost fire were measured, and compared with other test results. This paper providesanalysis and summary on the material properties of Q460and S460steel at hightemperature.（2）Residual stress distribution：The residual stress distribution of Q460steelcolumn before and post fire was measured by sectioning method. The welded residualstress distribution and residual stress redistribution at high temperature were simulatedby employing finit element method(FEM), and the simulated results were verifiedagainst measured results. The residual stress redistribution at different temperatures wasanalysed by validated FEM.（3）High strength Q460steel column stable loading capacity analysis: A FEmodel was established to analyse stable loading capacity of steel column, and wasvalidated by experimental results. The stable loading capacity of Q460steel column atroom temperature and high temperature were calculated by validated FE model with measured material properties, measured residual stress distribution at roomtempoerature and analysed residual stress distribution at high temperature. The stableloading capacity of Q460steel column predicted by FE model was compared with theresults calculated by different codes.（4）Experimental investigation of restrained high strength Q460steel column infire: A test programme on restrained steel column was carried out. The programmecomprised8full-scale substructures. The temperature distribution, axial and lateraldisplacement were measured in the test. The test results were analysed for determiningthe buckling temperature and failure temperature.（5）FE analysis of restrained high strength Q460steel column in fire: A2-D FEmodel and two3-D substructure FE models were established for thermal analysis andstructural analysis of tested specimen, respectively. FE results were verified against testresults. Analyse results showed that the validated FE models can simulate temperaturedistribution and structural response.（6）Parametric study of restrained high strength Q460steel column in fire：Asimplified finite element model was established in this paper, and the FE results wereverified by experimental data. Parametric studies were performed on restrained highstrength Q460steel column in fire using simplified finite element model. The analyticalparameters include residual stress, initial bend, load ratio, slenderness ratio, axialrestraint stiffness ratio and rotational restraint stiffness ratio.The results of the study show that： The residual stress of high strength Q460column significantly decrease at high temperature. American steel structural code couldpredict the ultimately bearing capability of high strength Q460steel, but, all the codescan not predict the ultimately bearing capability of high strength Q460steel at hightemperature. Fire resistance would be higher if the post-buckling behaviour isconsidered, residual stress, initial bend, axial load, slenderness ratio, axial restraintreduced the fire resistance of restrained steel column, but, rotational restraint increasethe fire resistance.