Journal of Constructional Steel Research 65 (2009) 1015–1028 Contents lists available at ScienceDirect Journal of Constructional Steel Research journal homepage: www.elsevier.com/locate/jcsr Review Plastic design of eccentrically braced frames, II: Failure mode control Luigi Mastrandrea * , Vincenzo Piluso University of Salerno, Department of Civil Engineering, Salerno, Italy article info Article history: Received 1 April 2008 Accepted 7 October 2008 Keywords: Eccentrically braced frames Limit design Collapse mechanism Capacity design Static non-linear analysis Local ductility demands abstract A design methodology aiming at the development of a collapse mechanism of a global type for eccentrically braced frames is presented in this paper. This result is of primary importance in earthquake resistant design, because partial and local failure modes are responsible of the worsening of the energy dissipation capacity leading to an increased risk of collapse under destructive ground motions. The proposed method is based on the assumption that horizontal member sections are known, as they are designed to resist internal actions due to vertical loads and design horizontal forces. Conversely, column and diagonal sections constitute the unknowns of the design problem. In particular, the presented approach also includes the influence of second order effects which are accounted for by means of the concept of mechanism equilibrium curve. The design requirements are derived by means of the kinematic theorem of plastic collapse. Column and diagonal sections are obtained by imposing that the mechanism equilibrium curve corresponding to the global mechanism has to lie below those corresponding to the undesired mechanisms within a displacement range compatible with the local ductility supply. Moreover, the introduction of the equivalent moment concept presented in a companion paper provides the proposed method with the ability to deal with short, intermediate and long links in the same manner. Aiming at the evaluation of the accuracy of the presented procedure, the inelastic performances of eccentrically braced frames designed by means of the proposed method are investigated, by means of static and dynamic non-linear analyses, in terms of collapse mechanism typology, available ductility and energy dissipation capacity. © 2008 Elsevier Ltd. All rights reserved. Contents 1. Introduction........................................................................................................................................................................................................................ 1016 2. Equilibrium curves of analysed mechanisms ................................................................................................................................................................... 1018 2.1. Mechanism equilibrium curve .............................................................................................................................................................................. 1018 2.2. Global mechanism ................................................................................................................................................................................................. 1019 2.3. Type-1 mechanisms............................................................................................................................................................................................... 1019 2.4. Type-2 mechanisms............................................................................................................................................................................................... 1019 2.5. Type-3 mechanisms............................................................................................................................................................................................... 1020 3. Design conditions for failure mode control ...................................................................................................................................................................... 1020 3.1. Basic requirements ................................................................................................................................................................................................ 1020 3.2. Conditions to avoid type-1 mechanisms .............................................................................................................................................................. 1021 3.3. Conditions to avoid type-2 mechanisms .............................................................................................................................................................. 1021 3.4. Conditions to avoid type-3 mechanisms .............................................................................................................................................................. 1022 3.5. Calculation of the parameters ρ im ......................................................................................................................................................................... 1022 4. Design of link sections ....................................................................................................................................................................................................... 1023 5. Evaluation of the axial load in the columns and in the diagonals at the collapse state ................................................................................................ 1023 6. Design algorithm................................................................................................................................................................................................................ 1023 7. Worked example ................................................................................................................................................................................................................ 1024 7.1. Structural scheme and preliminary design of links ............................................................................................................................................. 1024 7.2. Selection of design ultimate displacement .......................................................................................................................................................... 1025 * Corresponding address: University of Salerno, Department of Civil Engineering, via Ponte Don Melillo, 84084 Salerno, Italy. Tel.: +39 089 96 3411; fax: +39 089 96 4097. E-mail addresses: lmastrandrea@unisa.it (L. Mastrandrea), v.piluso@unisa.it (V. Piluso). 0143-974X/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcsr.2008.10.001