Seismic response of steel frames containing hierarchical friction-dissipating joints

Friction dissipating joints with slotted bolt holes have been used in concentrically braced frames (linear sliding) and more recently, in moment resisting frames (rotational sliding). Such joints have the ability to provide many cycles of ductile energy dissipation with little or no primary structural damage and permit the decoupling of the strength and stiffness of co nnected members. Suggestions are offered on the use of linear sliding joints in K-braced frames where they could lead to cheaper, stiffer structures with high levels of ductility. Rotating sliding bolted joints extend the benefits of damage-free energy dissipation to moment-resist ing frames. The decoupling of beam stiffness and end moment strength avoids over-sizing columns to deal with beam over-strength moments. The performance of a rotational slotted joint having a hierarchy of two distinct moment levels at which limited rotational slip can occur is di scussed. The basic characteristics of the joint are described and some observations made on the seismic response of some sample frames to seismic ground motion.