| In order to meet the requirement of the high strength and large thickness of building structure,a new type of high performance steel named by GJ steel was developed at Wuyang Iron & Steel Co.Ltd.The material performance requirements of high-rise and large-span building can be achieved by the GJ steel for its superior performance,especially the performance through the thickness direction.GJ steel has been applied in a number of landmark building projects in China.Currently,the GJ steel with the yield strength of 460 MPa is being increased adopted in the building construction,though the governing adopted is Q345 GJ steel.Research work on high strength steel has not been conducted intensively,especially for the high strength GJ steel.In order to achieve the application and popularization of GJ steel,in-depth research on the stability behaviour of columns fabricated from Q460 GJ steel in bending and axial compression was conducted in this current work.Based on the experimental study in conjunction with parametric analysis and reliability analysis,the behaviour of Q460 GJ steel columns under eccentric loading was investigated.The main research work can be summarised below:(1)The residual stresses of welded box and H-sectional columns fabricated from Q460 GJ steel were tested using sectioning method,the lengths of all the bending strips have also been corrected by circular curve method in this current work.A new method named by straightening measurement method was presented to measure the strip lengths directly in order to improve the accuracy and efficiency of the tests.The distributions of the residual stresses in welded box and H-sectional members fabricated from Q460 GJ steel were obtained and analysed.(2)Theoretical analysis of axially compressed column with rigid bodies in the ends was conducted,it has been demonstrated that effect of those rigid bodies on the test results is negligible.In the experimental study,the test machine with a loading capacity of 1000 ton was improved to set the pressure sensor at the column end to monitor the applied load.Moreover,the lateral displacements of the column ends have also been recorded to estimate the applicability of knife edge supports.The methods to measure the initial geometric imperfection were compared and discussed as well.(3)Experimental study for 8 welded box sectional and H-sectional columns under eccentric loading were carried out,corresponding experimental results were recorded and compared with different design codes.For the 8 welded box sectional columns,the width-thickness ratio was varied from 7.61 to 18.99 with a variety of slenderness ratio from 34.7 to 76.3.For the 8 welded H-sectional columns,the width-thickness ratio of the flange was varied from 3.01 to 6.04 with the height to thickness of the web was varied from 9.41 to 20.91.Besides,the slenderness ratio of the H-sectional columns was varied from 41.76 to 83.36.For both the box and H-sectional columns,four different eccentricity were considered.(4)Finite element model of the eccentric compression column was built and validated by the experimental results,which was followed by the parametric analysis.Four typical loading types,including eccentric load,transverse concentrated load,transverse uniformly distributed load and end bending moment were taken into account.16 different normalized slenderness ratio within the range from 0.5 to 3.5 were selected to analysis the stability behaviour and-curve of Q460 GJ welded box and H-sectional columns.(5)The parameters in the column curves of different design codes,including Chinese code,Europe code and American code were fitted and obtained,it has been proved that the column curve “b” in the mentioned codes can be adopted to design the welded box and H sectional Q460 GJ steel columns.The undetermined parameters in the calculation formula of column-bean in the Chinese were fitted,corresponding suggestions for those parameters for the above four different loading types were proposed.(6)Statistical parameters about material property uncertainties of Q460 GJ steel with the thickness range of no more than 35 mm were obtained.The statistical parameters of resistance uncertainties for Q460 GJ steel under eccentric loading have also been obtained by the comparison of the experimental results and design codes.Based on this,the partial safety factor of resistance and corresponding design parameter can be obtained according to reliability calculation.The main innovative points of this dissertation are below:(1)A new method named by straightening measurement method was developed to measure the length of the bending strips;(2)The method to achieve the boundary condition of spherical hinge at the column ends was proposed;(3)Experimental investigation on the stability behaviour of Q460 GJ steel column under eccentric loading was conducted and corresponding design parameters were obtained;(4)Resistance uncertain parameter and partial safety factor of Q460 GJ steel columns under eccentric loading were obtained and suggested. |
PDF Full Text Request