ELASTIC CRITICAL LOADS FOR PLANE FRAMES BY TRANSFER-MATRIX METHOD

The transfer matrix methodology is adapted to the stability analysis o f unbraced frames. A nonbranching chain of members is generated by par titioning the structure at floor levels. Geometric nonlinearity is acc ounted for by introducing the stability functions into the member stif fness and the flexural effect of axial forces into the equations of eq uilibrium. Field and station transfer matrices are derived on the basi s of a minimum number of only the essential degrees of freedom per flo or level. Displacements and internal forces are determined by a direct procedure that combines a gradual increase of the applied load with i teration at each load level. The critical load is located to a specifi ed degree of accuracy on the first singularity of the appropriate solu tion matrix. The developed formulation accounts for joint and base fle xibility as well as lateral load and fixed-end moments effects. The ac curacy and efficiency of its computer implementation are tested throug h comparison of its predictions with results obtained experimentally o r by other analytical methods.