Effects of Floor Diaphragm Flexibility in Reinforced Concrete Structures and Code Provision
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Date
2015-09
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Addis Ababa University
Abstract
All the seismic codes generally accept that in most cases the floor diaphragms may be modeled as fully rigid without in-plane deformability for reinforced concrete structures. Even though a rigid floor diaphragm is a good assumption for seismic analysis of the most buildings, several building configurations may exhibit significant flexibility in floor diaphragms. In these configurations, some codes like (EC8, EBCS8, EAK-2000) set certain qualitative criteria related to the shape of the diaphragm, while some others (UBC-97, ASCE7-05, FEMA-274, IS1893:2000) set quantitative criteria relating the in-plane deformation of the diaphragm with the average drift of the associated storey.
In this thesis a review of the provisions of some modern seismic codes for the analytical modeling of the floor diaphragm action is made and a methodology using finite elements models, taking into consideration the in-plane flexibility, for monolithic floor is suggested. Using this method with comparative response-spectrum dynamic analyses, some reinforced concrete structures with different plan shapes like L-shape, U-shape, rectangular and rectangular with opening according to EC8 &UBC-97 are analyzed. Then, the mode period curve, story deformation curves and story shear with story curve and the results so obtained are compared to analyses the effect of in plane flexibility of diaphragm in multi -story building.
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Civil Engineering