The 14 th World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China INDIVIDUAL TESTING OF DISSIPATIVE BUCKLING RESTRAINED BRACES G. Palazzo 1 , F. López-Almansa 2 , X. Cahís 3 and F. Crisafulli 4 1 Ceredetec, National Technological University, Mendoza, Argentina 2 Architecture Structures Department, Technical University of Catalonia, Barcelona, Spain 3 Mechanical and Construction Engineering Department, University of Girona, Girona, Spain 4 Faculty of Engineering, National University of Cuyo, Mendoza, Argentina ABSTRACT This work presents the results of experiments on four prototype buckling restrained braces. The devices were designed and built by the authors; consist basically of a steel cylinder as dissipative core and a steel tube filled with mortar as buckling restrainer casing. The design and production issues are accounted for in an integrated way and all the adopted technical solutions are fully explained. The experiments consist of imposing to the prototype devices axial cycling strain up to failure. The results of the tests are deeply described and discussed. The main conclusion of this work is that it is possible to obtain a reasonably cheap, efficient, robust, low maintenance and durable prototype device requiring only a low-tech production process. KEYWORDS: Energy dissipators, Buckling restrained braces, Passive control, Testing, Fatigue life. 1. INTRODUCTION Energy dissipators are a convenient option for earthquake-resistant design of buildings and other civil engineering constructions since they absorb most of the input energy thus protecting the main structure from damage even under strong seismic motions. Several types of devices have been proposed; those based on plastification of metals are simple, cheap and reliable while have shown repeatedly their usefulness. Among them, the buckling restrained braces are one of the dissipators more used for seismic protection of building frames. Consist of slender steel bars connected usually to the frame to be protected either like concentric diagonal braces or like chevron braces. Under horizontal seismic motions, the interstory drifts generate axial strains in such steel bars beyond their yielding points; their tension-compression cycles constitute the hysteresis loops. The buckling of these bars is prevented by embedding them in a stockiest encasing. Such encasing is usually formed by steel elements filled with mortar. Some sliding interface between the steel core and the surrounding mortar is required to prevent excessive shear stress transfer since it would reduce the longitudinal stress in the core thus impairing the energy dissipation. The buckling restrained braces posses several relevant advantages compared to other hysteretic devices:  The ratio dissipated energy / added material is the highest in the comparative devices [Palazzo & Crisafulli, 2004]; the added material includes dissipators, bracing and connections. The degree of plastification is uniform along the whole body of the core.  These dissipators constitute themselves a bracing system and no additional braces are required to connect each device to the main frame.  A relevant experience is available since a number of individual and subassemblage tests have been carried out [Black, Makris & Aiken, 2004; Usami, Kasai & Kato 2003; Lopez et al. 2004;