Notional load approach for shear-type braced frames

A notional load approach used in braced frames was proposed to avoid the complexity in determining the effective length of columns during the design of steel structure.Notional loads were applied on the storey levels,and second order elastic analysis was conducted together with other loads.Columns were designed based on their system lengths.A formula was derived for the notional loads in cases of with and without horizontal load.Results showed that the notional load was independent of the horizontal load.A series of braced frames under different geometric and load conditions were analyzed by geometric and material nonlinear analysis(FEA) considering member initial bow,initial sway imperfection and residual stress.An approximate formula for the notional load was proposed and compared with the FEA results.The accuracy of the formula in practical application was verified through analysis of practical examples.