Research On Values For Moment Amplification Factors Of Columns Based On A3-D Frame Without Yielding Of Columns Ends

In Chinese Seismic Code, flexural bearing capacities of columns and beams aredifferent by means of moment amplification factors of columns; lead main of yieldpositions appear in framework beam in large earthquake, framework forms reasonableenergy dissipation mechanism, at the same time framework redistribution of internalforces and energy dissipation capability, holding a well ability of collapse resistant inearthquake, Therefore the reasonable value of the moment amplification factors ofcolumns is critical. Frame structure designed according to2001version of the "Code forseismic design of buildings", most of them did not form reasonable energy dissipationmechanism, some even collapsed, and the value of moment amplification factors ofcolumns has been dramatically increased in the2010version of the "Code for seismicdesign of buildings". How much the number of value is enough, in other words columnend do not yield in large earthquakes need how much the number of value of momentamplification factors of columns.In this paper，7degrees0.1g area space frame structure is designed in accordancewith the2010version of the "Code for Seismic Design of buildings", In creating anon-linear model, artificially raise the column longitudinal reinforcement yield strength,so that it does not yield under strong earthquakes, other materials is normally simulate,Select30groups of ground motion records by using the SRSS spectrum-election wavemethod, structure was respectively input selected ground motion records, extracttime-history force of column end except the bottom sections of columns time-historyforce, the time-history forces is used to calculate bearing capacity by using programwhich based on the sections do not yield subjected to biaxial eccentric compressionProgramming two procedures which calculating bearing capacity of sectionsubjected to biaxial eccentric compression by using MATLAB,which are provided by2010edition of "code for design of concrete structures", including nikeqin formula andcalculation method in Appendix E, Resolve the value of the iterative initial valueproblem, based on the definition of whether the section yields, make some changes onbiaxial eccentric compression program which based on limit state, get biaxial eccentriccompression program which based on sections do not yield, using OpenSees softwarecheck the program, the results show the program has high precision and accuracy.According to the biaxial eccentric compression program which based on section does not yield calculated section longitudinal reinforcement area, thus deduce themoment augment factor of column of the section, Re-design framework according to theproposed moment augment factor of column values，the framework was input largeearthquake level of seismic waves, investigating the response of framework, evaluatingthe effect of the proposed values.The following conclusions are obtained through the works mentioned above:①The design of the frame column based on which does not yield on the largeearthquake, calculating the bearing capacity of the column section using the methodbased on the section does not yield. If the ground motion is bi-direction seismic input,use the method which based on section does not yield subjected to biaxial eccentriccompression calculating the bearing capacity of column section.②The demand of moment amplification factors of columns to the Symmetricalcolumns in plane position are the same, the demand of node upper and lower columnsection are different, values obtained according to the seismic code formula6.2.2-1,demand of η_c-calare generally small in the each sections of corner columns, demand of η_c-calare generally big in the each sections of middle columns,③Although the η_c-calvalue obtained according to the seismic code formula6.2.2-1bigger than1.3in the7degrees0.1g area, seismic measures such as minimumreinforcement ratio often cover up this insufficient.