Stiffness-based approach for Belleville springs use in friction sliding structural connections

Sliding hinge joints (SHJs) used in beam-to-column connections of moment frames have a moment-rotational behaviour that depends on asymmetric friction connection (AFC) sliding behaviour. The AFC is also applied to column base connections and friction sliding braces. In the AFC, the slotted sliding plate is clamped between one ideally fixed surface and one partially floating surface. In current practice, the AFC bolts are fully tensioned at installation (i.e. yielded) to provide the clamping force. The AFC bolts are subjected to moment, shear, and axial force (MVP) interaction during joint sliding that is expected to occur only in severe earthquake shaking. The AFC bolt tension as well as SHJ elastic strength are reduced after a few sliding cycles. In this paper, the reasons for the AFC bolt tension loss are discussed, and solutions to prevent this bolt tension loss, including the optimum use of Belleville springs (BeSs) and installing the bolts within the elastic range, are proposed. This paper analytically shows that these solutions can generate significantly improved retention of AFC bolt tension, improved AFC sliding behaviour, higher displacement capacity to accommodate prying effects, and better AFC self-centering characteristics. Examples of AFC bolt installation within elastic range and tension loss with and without BeSs are provided. Similar models are developed for symmetric friction connections (SFCs) and compares differences in behaviour.