RESUMO
Use of steel bracing systems for seismic strengthening of existing structures, especially those of RC and masonry, has become quite popular in recent years. However, little information is available on the behavior of frame-bracing systems under large cyclic deformations, and on rational procedures for the design of added bracing systems. Current practice is concerned with designing bracing for added strength and stiffness only with little or no regard for providing ductility or energy dissipation capacity into the system. The results of a two-thirds scale model of a two story RC frame strengthened by a ductile steel bracing system are briefly discussed in this paper. The strengthened frame showed stable and "full" hysteretic loops, and excellent ductility and energy dissipation under cyclic story drifts up to 3 percent. Also discussed in the paper are some connection problems that need to be considered in the design of such strengthening scheme (AU)