EFFECTS OF CONNECTION STIFFNESS AND PLASTICITY ON THE SERVICE LOAD BEHAVIOR OF UNBRACED STEEL FRAMES

Accurate determination of the relative restraint of beam-to-column con nections is important for both the strength and serviceability of stru ctural frames. Overestimating the connection restraint can result in u nderestimating lateral sway and underestimating the connection restrai nt can lead to underestimating forces developed in the beams and colum ns. Both conditions can influence structural instability. This paper e xamines the effects that certain connection parameters have on the ser viceability limit state of unbraced steel frames. The connections are modeled as elastic-perfectly plastic and are described by their elasti c stiffness and the ultimate moment capacity. The second order P-delta effects are included. The effect of connection geometry on lateral sw ay for an unbraced, 3-bay and 5-story office building is studied. Thre e types of bolted connections: single and double web-angle, top- and s eat-angle, and top- and seat-angle with double web-angles are examined and their effect on lateral sway is compared with and without second order P-delta effects.