Research On Design Indexes Of Q460GJ Steel

With the rapid development of building steel structure in China,super high-rise buildings and large-span space structures have sprung up.In order to satisfy the need of the development trend of high-strength steel for building structures and meet the increasing demand for thick plate structures,Chinese domestic steel plates for building structure(refer to as GJ steel)came into being.The performance of GJ steel is superior to that of low-alloy high-strength structural steel of the same grade,and GJ steel has been applied in major domestic engineering projects.The new version of Chinese “Standard for design of steel structures” has listed the design value of Q345 GJ and Q460(low-alloy steel),but no the design indicators of Q460 GJ steel.To increase the research accumulation of Q460 GJ and promote its engineering applications,this paper conducts research on the design indexes of Q460 GJ steel.Based on a total of 136 surveys and independent tests of the Q460 GJ steel material performance data,the material performance uncertainty and its statistical parameters of the two thickness groups of t≤16mm and 16 mm <t≤50mm were obtained.And the hypothesis test was done to determine the distribution type of yield strength of the two thickness sets of Q460 GJ.According to the measured values of the overall stable bearing capacity of 22 Q460 GJ steel axial compression members,16 compression-bending members and 30 bending members obtained from the test,the calculation modes uncertainty and its statistical parameters of the three kinds of members were determined.Combining the statistical parameters of material performance uncertainty,calculation modes uncertainty and geometric uncertainty data that in previous studies,statistical parameters of the resistance uncertainty of three types of members were obtained.typical load and their combinations,target reliability index,load partial coefficients specified in the “Unified standard for reliability design of building structures” that Implemented in 2018 and other relevant parameters were selected,and the first-order second-moment reliability method(JC Method)was chosen to solve the resistance partial coefficients of the three types of members under each load combination,load ratio and variable load ratio.Based on the solved partial resistance coefficients,the recommended values of compressive and bending design indexes are determined.And other design indexes such as tensile design value,end pressure value were obtained by previous design index determination method.Finally,the reliability of the axial compression members,compression-bending members and bending members were checked and analyzed under the real resistance partial coefficients corresponding to the recommended design indexes.And design recommendations are given based on the reliability analysis results.