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Computers and Concrete Volume 25, Number 3, March 2020 , pages 273-282 DOI: https://doi.org/10.12989/cac.2020.25.3.273 |
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Effects of diaphragm flexibility on the seismic design acceleration of precast concrete diaphragms |
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Dichuan Zhang, Robert B. Fleischman and Deuckhang Lee
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| Abstract | ||
| A new seismic design methodology for precast concrete diaphragms has been developed and incorporated into the current American seismic design code. This design methodology recognizes that diaphragm inertial forces during earthquakes are highly influenced by higher dynamic vibration modes and incorporates the higher mode effect into the diaphragm seismic design acceleration determination using a first mode reduced method, which applies the response modification coefficient only to the first mode response but keeps the higher mode response unreduced. However the first mode reduced method does not consider effects of diaphragm flexibility, which plays an important role on the diaphragm seismic response especially for the precast concrete diaphragm. Therefore this paper investigated the effect of diaphragm flexibility on the diaphragm seismic design acceleration for precast concrete shear wall structures through parametric studies. Several design parameters were considered including number of stories, diaphragm geometries and stiffness. It was found that the diaphragm flexibility can change the structural dynamic properties and amplify the diaphragm acceleration during earthquakes. Design equations for mode contribution factors considering the diaphragm flexibility were first established through modal analyses to modify the first mode reduced method in the current code. The modified first mode reduced method has then been verified through nonlinear time history analyses. | ||
| Key Words | ||
| diaphragm flexibility; seismic design; precast concrete diaphragm; modal analysis; nonlinear time history analysis | ||
| Address | ||
| Dichuan Zhang: School of Engineering and Digital Sciences, Narzarbayev University, Kazakhstan Robert B. Fleischman: Department of Civil Engineering and Engineering Mechanics, University of Arizona, USA Deuckhang Lee: Department of Architectural Engineering, Chungbuk National University, Korea | ||