Performance-Based EvaIuation of Rectangular RC Structures Using a Flexible Diaphragm Model

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Title: Performance-Based EvaIuation of Rectangular RC Structures Using a Flexible Diaphragm Model

Author(s): J. M. Barron and M. B. D. Hueste

Publication: Special Publication

Volume: 209

Issue:

Appears on pages(s): 641-660

Keywords: building diaphragms; FEMA 273; nonlinear analysis; performance evaIuation; seismic analysis

Date: 9/26/2002

Abstract:
Under seismic loading, floor and roof systems in reinforced concrete (RC) buildings act as diaphragms to transfer lateral earthquake loads to the vertical lateral force resisting system (LFRS). In current practice, horizontal diaphragms are typically assumed to be rigid, thus neglecting the effect of the in-plane movement of the diaphragms relative to the vertical LFRS. This study focuses on evaluating the impact of diaphragm flexibility on the structural response of typical RC rectangular building structures using a performance-based approach. Three-story and five-story RC buildings with end shear walls and two aspect ratios (approximately 2: 1 and 3: 1) were developed and designed according to current code procedures assuming rigid diaphragm behavior. The performance-based design criteria outlined in the NEHRF' Guidelines for Seismic Rehabilitation of Buildings (FEMA 273) (4) were used to assess the adequacy of the four case study buildings when diaphragm flexibility was included in the structural response. It was found that the use of a flexible diaphragm model had the largest impact on the 3-story, 3: 1 aspect ratio building and the various analysis procedures gave differing assessments of the adequacy of this case study building. The remaining three case study buildings generally satisfy the FEMA 273 acceptance criteria for three performance levels based on an evaluation of critical structural elements.