Overall Elastic Stability of Multistory Buildings

Procedures are presented for the three-dimensional analysis of the overall elastic stability of multistory buildings and for the inclusion of stability effects in lateral-load analysis. The effect of axial force on the flexural stiffness of individual members is neglected. Floors are treated as diaphragms that are rigid in the horizontal plane. The suggested procedures do not require the solution of nonlinear systems of equations or nonlinear eigenvalue problems. The proposed techniques were used to study several 20-story buildings whose structural framing systems were designed in accordance with current engineering practice. The results of these analyses indicate that buildings that are designed without regard to overall elastic stability can have very low factors of safety against elastic buckling, especially in a torsional mode; second-order effects can cause substantial increases in the displacements and stresses due to wind and other horizontal loads.