Dissipative connections with U-shaped steel plate for braces of concentrically braced frames

Abstract

In concentrically braced frames, braces-to-adjacent member connections are suitable locations for the dissipation of seismic energy. If the implementation of dissipative connections does not compromise the global lateral stiffness of the structure, the compression braces can then be protected from buckling, while the structural ductility is increased and the action effects reduced. Furthermore, an efficient use of dissipative connections allows reducing the cost of post-earthquake interventions. In this paper, an innovative dissipative connection for braced frames is proposed, consisting of a steel plate bent to a U shape and connecting the brace to the adjacent column. In this connection, energy dissipation is obtained through the inelastic flexural deformation that takes place in the plate. This paper presents experimental results on the isolated U-connection and on single-storey concentrically braced frame (real scale) including the U-connection. Besides considering several variations on the geometry of the U-shape plate, the tests considered both monotonic and cyclic loading. The results highlight the efficiency of the U-connection to dissipate the energy input through inelastic deformations. On the other hand, the cyclic tests show however that the connection is potentially sensitive to fatigue, as the deformation capacity is significantly reduced with repeated loading and increasing stress amplitude, requiring thus specific attention in practical design situations.