Seismic Symmetric Friction Dissipater for Steel Braced Frames

Braces with friction connections can provide seismic dissipation. They are assembled by slotting the gusset plate, providing high hardness plates at both sides of the gusset plate, and clamping these plates to the brace end. After several displacement excursions, the gusset plate may need to be replaced due to surface degradation. This replacement is expensive and time consuming. A dissipater for braces detailed for easy and fast replacement is proposed and termed the Symmetric Brace Dissipater (SBD). SBDs comprise a shaft and a sleeve, both with square hollow sections. Slotted holes are provided on two opposite sides of the sleeve, and dismountable slotted plates are bolted on the sleeve matching its slotted holes. High hardness plates are clamped on top of the dismountable slotted plates by means of high strength proof loaded bolts crossing both the sleeve and the shaft. In SBDs energy is dissipated as the shaft moves relative to the sleeve. Quasi-static testing of three SBDs was undertaken. It is shown that the SBDs hysteresis loop shape is almost rectangular, and its plateau corresponds to the force producing the sliding of the sleeve. This force slightly reduced with the cyclic loading due to bolt tension loss. A SBDs sliding mechanism is proposed considering an initial limited sliding of the sleeve and the high hardness plates and followed by the full sliding of the sleeve.