An Alternative Procedure for Seismic Analysis and Design of Tall Buildings F. Naeim, L. D. Carpenter, T. Ghodsi, G. C. Hart, M. Lew, M. Mehrain, T. A. Sabol and J. W. Wallace John A. Martin & Associates (FN), WHL International (LDC) , Englekirk Partners (TG), Weidlinger Associates (GCH), AMEC Environment & Infrastructure (ML), URS Corporation (MM), Englekirk Institutional (TAS), University of California Los Angeles (JWW); Los Angeles Tall Buildings Structural Design Council, Los Angeles, CA, USA (All) SUMMARY: Building codes intend to provide for safe buildings by prescribing loads and material properties as well as structural detailing generally address all building types and construction. However, building codes may not provide for the most economical, efficient, and safe tall buildings because the codes are general and prescriptive in nature. Tall buildings are really a special class of buildings that have unique qualities and characteristics. Tall buildings are recognized to be designed with a different approach to meet safety and performance requirements, especially in regions with high seismic activity. To meet this need, an alternative procedure for seismic analysis and design of tall buildings in the Los Angeles region was developed by the Los Angeles Tall Buildings Structural Design Council (LATBSDC). The Council has been developing the alternative design procedure over eight years and recently published the third edition of the procedure. Keywords: Tall buildings, performance-based engineering, seismic design, building codes, alternative procedure 1. INTRODUCTION The 2011 LATBSDC procedure provides a performance-based earthquake engineering (PBEE) approach for seismic design and analysis of tall buildings with predictable and safe performance when subjected to strong earthquake ground motions. The intent of the procedure is to result in more accurate identification of the relevant demands on tall buildings thus providing for structures that effectively and reliably resist earthquake forces. The performance-based alternative procedure requires an in-depth understanding of ground shaking hazards, structural materials behavior, and nonlinear dynamic structural response. In particular, the implementation of this procedure requires proficiency in structural and earthquake engineering including knowledge of: seismic hazard analysis and the selection and scaling of ground motions; nonlinear dynamic behavior of structural and foundation systems; mathematical modeling capable of reliable prediction of nonlinear behavior; capacity design principles; and detailing of elements to resist cyclic inelastic demands, and assessment of element strength, deformation and deterioration under cyclic inelastic loading. The aim is to provide: a more reliable seismic performance; reduced construction cost; relief from prescriptive design requirements that do not apply; accommodation of architectural features; and use of innovative structural systems and materials not currently allowed by the building code. 2. WHY IS AN ALTERNATIVE PROCEDURE NEEDED? The basic reason why an alternative design procedure for tall buildings in seismic regions is needed is simply that our building codes are not currently adequate to address the nature and characteristics of tall buildings. The building codes are a “one size fits all” approach to the design of structures and especially to the seismic design of structures; the building codes apply to all buildings – short, medium or tall. Building codes are generally prescriptive in nature with rules about what structural systems or materials can be used and what material properties are acceptable. In general, modern building codes