EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS Earthquake Engng. Struct. Dyn. 27, 543—556 (1998) NUMERICAL EFFICIENCY ASSESSMENT OF ENERGY DISSIPATORS FOR SEISMIC PROTECTION OF BUILDINGS D. FOTI, L. BOZZO AND F. LO PEZ-ALMANSA *  Technical University of Catalonia, Department of Architecture Structures, Avda. Diagonal 649, 08028 Barcelona, Spain  University of Girona, Department of Construction Engineering and Architecture, Avda. Lluı & s Santalo & s/n, 17003 Girona, Spain SUMMARY This paper presents a two-dimensional numerical study on the nonlinear seismic response of buildings equipped with two types of energy dissipators: Constant Friction Slip Braces (CFSB) and Adding Damping and Stiffness (ADAS). Three types of reinforced concrete buildings with 3, 7 and 15 storeys, representatives of the short-medium- and long-period ranges, are considered. Dissipators are placed in steel diagonal braces in all the floors. The sliding threshold (or yielding) forces for each mechanism are selected using two different criteria: (i) they are taken as 50, 75 and 100 per cent of those generated by the equivalent static lateral forces recommended by the UBC-91 for a ductile moment resisting frame and (ii) they are constant in the whole building (this constant value is chosen equal to the maximum forces obtained with the previous criterion). The input consists of ten recorded earthquakes (normalized with respect to their Housner intensity) corresponding to medium and stiff local soil conditions. Average values on the ten registers are given for the maximum horizontal displacement, the base shear, the energy dissipated and the interstorey drift. The possibility of failure in some devices has been numerically simulated to assess the robustness of the system. The obtained results show that both devices are useful to reduce the response compared to the bare frame and that CFSB is more efficient than ADAS; for 7- and 15-storey frames the lateral displacement with CFSB is even smaller than the one for the braced frame (rigid connections instead of dissipators). The conclusions are expected to provide simple design guidelines.  1998 John Wiley & Sons, Ltd. KEY WORDS: ADAS; CFSB; energy dissipators; preliminary design; parametric assessment; passive control 1. INTRODUCTION Much of the existing research in energy dissipation systems focuses on experimental testing of particular devices and in a lower extent there are numerical analysis of buildings equipped with dissipators. Several papers presenting design rules have been published but there is not a comprehensive study on the seismic efficiency of such systems. This paper presents a numerical nonlinear parametric assessment on the seismic response of buildings equipped with energy dissipation devices. The study consists of assessing the 2-D seismic dynamic response of three reinforced concrete frames (with, respectively, 3, 7 and 15 storeys) equipped with energy dissipators. This research shows that such devices are efficient to reduce earthquake induced forces and at the same time maintaining interstorey drifts between reasonable bounds provided their number is enough and they are properly designed. In this paper the * Correspondence to: F. Lo´ pez-Almansa, Departamento de Estructuras en la Arquitectura, ETSAB (UPC), Avda. Diagonal, 649, 08028 Barcelona, Spain. E-mail: lopez@ea.upc.es Contract/grant sponsor: DGICYT; Contract/grant number: PB92-075 Contract/grant sponsor: European Commission; Contract/grant number: ERBCHBICT 941821 CCC 0098—8847/98/060543— 14$17)50 Received 25 June 1997  1998 John Wiley & Sons, Ltd. Revised 1 August 1997