Important Developments in the Seismic Design of Diaphragms
ASCE 7-16 includes two significant new items related to the seismic design of diaphragms. First, a new Section 12.10.3, Alternative Design Provisions for Diaphragms including Chords and Collectors, has been added to Section 12.10, Diaphragm Chords and Collectors. The new section provides for an alternative determination of diaphragm design force level, which is mandatory for precast concrete diaphragms in buildings assigned to Seismic Design Category (SDC) C or above. The alternative is permitted to be used for other precast concrete diaphragms, cast-in-plane concrete diaphragms, and wood diaphragms supported on wood framing. All diaphragms other than precast concrete diaphragms in SDC C, D, E, or F buildings may continue to be designed using the design force level in ASCE 7-16 Section 12.10.1, which is unchanged from ASCE 7-10.
To go hand-in-hand with the alternative diaphragm design force level, ASCE 7-16 includes a precast diaphragm design procedure in Section 14.2.4, which is based on extensive research. The procedure must be used whenever the design force level of Section 12.10.3 is used. The requirements of Section 14.2.4 are in addition to the requirements of ACI 318-14 Section 18.12, Diaphragms and Trusses.
The procedure gives the designer three diaphragm design options for selecting the target performance of a diaphragm when subject to earthquake excitation. The Elastic Design Option (EDO) seeks to keep the diaphragm elastic in the Maximum Considered Earthquake (MCE). The Basic Design Option (BDO) seeks to keep the diaphragm elastic in the design earthquake while permitting controlled inelastic behavior in the MCE. The Reduced Design Option (RDO) permits controlled inelastic behavior even in the design earthquake. The choice of options is not unrestricted, but depends on the seismic design category, the number of stories, the diaphragm span, and the diaphragm aspect ratio.
The seminar explains the alternative diaphragm design force level as well as the precast diaphragm design procedure of ASCE 7-16.
Dr. S. K. Ghosh is known internationally for his work in earthquake engineering. He has influenced seismic design provisions in the United States for many years by serving on or chairing numerous committees and advisory panels. He specializes in the analysis and design, including wind and earthquake resistant design, of reinforced and prestressed concrete structures. Dr. Ghosh is active on many national technical committees and is a fellow of ASCE, SEI, ACI, and PCI. He is a member of ACI Committee 318, Standard Building Code, and the ASCE 7 Standard Committee (Minimum Design Loads for Buildings and Other Structures). He is a former member of the Boards of Direction of the Building Seismic Safety Council (BSSC), the American Concrete Institute (ACI), and the Earthquake Engineering Research Institute (EERI). In addition to authoring many publications in the area of structural design, he has investigated and reported on structural performance in recent earthquakes.
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|Speakers||S. K. Ghosh|