LIMIT TORQUE FOR A FRICTIONAL JOINT

A friction limit moment (torque) is derived for a one-bolt, two-member structural joint. Once the structural load reaches the limit moment, the frictional resistance in the joint is overcome and relative rotati on of the structural members can occur. A framework based on the kinem atical approach of limit analysis is proposed to calculate the Limit t orque. While only the simple case of calculations is presented in this paper, more complex joints can be analyzed using the approach propose d. The friction limit loads derived using this approach can be represe nted as a surface in a generalized stress space, analogously to the yi eld condition of plasticity. Upon the structural load reaching the thr eshold (limit) friction load, the process of relative movement of stru ctural elements (rotation and translation) becomes possible until the joint locks up due to structural constraints. Results have application in analysis of structures with gaps in their joints, particularly str uctures with deliberately introduced gaps. The response of such struct ures to loads can differ significantly from those where gaps are not p resent, and some benefits can be gained, e.g., an increase in the rang e of the elastic response. Application also can be envisioned in syste ms that are required to dissipate energy.