Therefore, this book is aimed at structural engineering professionals, graduate students and advanced civil engineering students, with the purpose of presenting the fundamental aspects of seismic-resistant design of steel structures. This task is carried out with the conviction that the training of structural engineers represents an effective action to reduce the vulnerability of buildings. This text was originally edited in 2010 and updated in 2012, primarily to incorporate modifications introduced in ANSI/AISC 341-10, Seismic Provisions for Structural Steel Buildings. In addition, two new chapters were added on structural systems with very good performance, such as buckling-restrained braced portal frames and steel plate shear walls. The third edition included the main aspects of the design of structures with steel and concrete composite members. This topic is considered to be highly topical, since composite constructions represent an alternative with very good structural performance and constructive and economic advantages, as a result of the synergic combination of structural steel and concrete. In 2014, the fourth edition was presented, in which an example consisting of the design and calculation of a building with a steel structure formed by unbraced and concentrically braced portal frames has been added, and a complete chapter on the behaviour of the different types of steel structures was included. In addition, the contents related to the following topics were expanded: design for performance, column-base connections, joints, braces with concrete-filled tubes, eccentrically braced frames with vertical connections, coupled walls, connections for composite frames, etc. The fifth edition is now presented, in which the main modifications are related to the new version of ANSI/AISC 341-16, Seismic Provisions for Structural Steel Buildings. The most significant changes introduced in the ANSI/AISC 360-16, Specification for Structural Steel Buildings and ASCE/SEI 7-16 regulations have also been considered. Minimum Design Loads for Buildings and Other Structures, since these are directly linked to the first one. In addition, the basic concepts of seismic-resistant design and structural calculation presented in Chapters 1 and 2 have been expanded. Among the main topics included in the fifth edition are the Direct Analysis Method to consider effects of geometric nonlinearity and imperfections and the concepts of design by capacity that are explicitly incorporated in the analysis to determine the required strength of structural members and components that remain in elastic range. Thus, seismic actions limited by capacity are defined for the different structural types, Ecl. Other important aspects are the general update of the design requirements for the different structural types and the presentation of the new specific design requirements for multi-tiered braced frames (MTBF). The description of the prequalified connections defined in ANSI/AISC 358-16, Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications, has also been updated. As for the format of the document, associative links and cross-references are used (for example to link the references with the text where they are mentioned) in order to facilitate and speed up the reading of the digital document. My special thanks to the Asociación Latinoamericana del Acero, Alacero, which, in its eagerness to promote and spread the use of steel in Latin America, proposed and supported the production of this publication, in all its editions. In particular, I would like to highlight the constant support of its directors, Guillermo Moreno and Rafael Rubio, and especially Alberto Pose, for the development of the work. The opinions, suggestions and comments received from professionals, professors and engineering students from Latin America are very welcome and have undoubtedly contributed to improve the clarity of the text. Based on these contributions, clarifications have been included and some topics have been further developed in this edition. It is important to highlight the work carried out by the Eng. Eduardo Daniel Quiroga, who provided comments and suggestions related to technical aspects of the publication, and Mr. Alejandro Santoro, who also collaborated in the preparation of some graphics. 3 I am also grateful for the contribution of Professor Silvina Negri to improve the wording of the first edition of the text. Finally, my thanks and dedication for this work to Vicky, Marco, Francisco, Santiago and Sebastián.

Francisco Javier Crisafulli, Civil Engineer, Ph.D. Professor of Structural Engineering, Universidad Nacional de Cuyo, Mendoza, Argentina Mendoza, March 2018.