Effects of Translational Restraint on Frame Buckling.

摘要

When an elastic rigid-jointed frame buckles,each member is restrained elastically by the adjacent members. The restraints may be positive in which case they stabilize the member,or negative in which case they disturb the member and reduce its resistance to buckling. The member end restraints may be both rotational and translational. The present design practice is to allow for positive elastic rotational restraints,and this is usually done by using effective length charts or nomograms. However,these are only available for the two special translational restraint cases of zero and infinite restraint,and these are applied to unbraced and fully braced frames respectively. It is shown in this paper that there may be intermediate cases of translational sway restraint,even in unbraced frames. The mechanism for this effect is demonstrated. The buckling of a member with elastic rotational and translational restraints,both positive and negative,is then analyzed,and the solutions are presented in a simple effective length diagram. The use of this diagram is demonstrated by determining the elastic buckling loads of some example frames.