Ingenieria

Conceptual Seismic Design of Regular Frames Based on the Concept of Uniform Damage
Kyungha Park1 and Ricardo A. Medina, M.ASCE2
Abstract: The objective of this study was to propose a seismic design methodology for moment-resisting frames to limit the extent of structural damage and distribute this damage uniformly along the height. This permits the efficient utilization of the energy dissipationcapacity of most structural members to avoid undesirable dynamic responses, e.g., the formation of story mechanisms and/or the amplification of story drifts caused by P–delta effect. The proposed methodology is based on the utilization of seismic design lateral load patterns to obtain a uniform distribution of story ductility ratios along the height. It is demonstrated that, on average, framestructures designed based on the proposed approach exhibit a more uniform distribution of story ductility and story drift ratios when compared to the distributions obtained using current U.S. seismic code provisions. Designs based on the proposed approach are expected to provide increased protection against global collapse and loss of life during a strong earthquake event. DOI: 10.1061/ ASCE 0733-94452007 133:7 945 CE Database subject headings: Seismic design; Conceptual design; Deformation; Frames; Inelastic action; Damage.

Introduction
Code-compliant designs for regular moment-resisting frame structures in the United States rely on estimates of seismic lateral force demands to determine the strength and stiffness characteristics of the lateral-load resisting system during the conceptualdesign phase of a project. Estimates of seismic lateral force demands are based primarily on the ordinates of elastic design spectra that are given for a specific ground motion hazard level, the fundamental period of the building, and its expected distribution of mass and stiffness over the height. These estimates are obtained from the application of elastic structural dynamics concepts withoutexplicitly considering the inelastic behavior of the lateral-load resisting system. Therefore, code-complaint lateralload distributions are more accurate for the estimation of inertial loads of structural systems designed to satisfy a high performance level, e.g., structures that are required to remain functional when exposed to relatively small but frequent earthquake events. Under larger, lessfrequent earthquake events and in the absence of energy dissipation devices e.g., dampers , the expectation is that a seismic design based on current procedures will fulfill the performance target of life safety, i.e., cyclic dynamic behavior without local or global collapse at the expense of perhaps significant structural damage. Strictly speaking, the designer has certain conGraduate ResearchAssistant, Dept. of Civil and Environmental Engineering, Univ. of Maryland, College Park, MD 20742. E-mail: kyunghap@gmail.com 2 Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Maryland, College Park, MD 20742 corresponding author . E-mail: ramedina@umd.edu Note. Associate Editor: Rakesh K. Goel. Discussion open until December 1, 2007. Separate discussions must be submittedfor individual papers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and possible publication on December 28, 2005; approved on December 8, 2006. This paper is part of the Journal of Structural Engineering, Vol. 133, No. 7, July 1, 2007. ©ASCE, ISSN 0733-9445/2007/7-945–955/$25.00.
1trol over the global damage the structure will experience by making appropriate choices of strength, stiffness, and detailing requirements, but has very limited control over the distribution of damage in the system. An important component of performance-based seismic design is the implementation of rational procedures to assist engineers in the decision-making process at the conceptual design...