Diaphragm effects in rectangular reinforced concrete buildings

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 their in-plane movement relative to the vertical LFRS. The objective of this study is to evaluate the impact of in-plane diaphragm deformation on the structural response of typical RC rectangular buildings 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 FEMA 273-NEHRP Guidelines for Seismic Rehabilitation of Buildings 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 three-story, 3:1 aspect ratio building and that the various analysis procedures in FEMA 273 gave differing assessments of the adequacy of this case study building. The remaining three case study buildings generally satisfy the FEMA 273 acceptance criteria based on an evaluation of critical structural elements for three performance levels. 2004.

Diaphragm effects in rectangular reinforced concrete buildings Academic Article