NONLINEAR-ANALYSIS OF STRUCTURAL-STEEL FRAMES

Material, geometrical and connection non-linearities could have a sign ificant influence on the forces and moments in a steel structure, espe cially in sway frames at ultimate load levels. Some structural steel d esign codes (such as CAN3-S16-1-M89) require that a designer consider second-ol der moments (i.e. the geometric non-linearities). if the ste el members are able to redistribute moments through plastic hinge form ation, it makes economic sense to do a plastic design. Certain so-call ed 'hinge'-connections do in fact transfer significant moments. It wou ld thus also make the structure more economical if one can take this m oment transfer into account. All the above effects could be built into a steel frame analysis program. In this paper, ways of including geom etrical, material and connection non-linearities into the matrix stiff ness method in a relatively uncomplicated manner will be discussed. A computer program developed by the authors, for design-office use, wher e the matrix stiffness method has been adjusted to incorporate all the se non-linearities is described. The use of the computer program is il lustrated by means of an example.