Construction Loads and Serviceability Requirements: Deflection Control, Span/Thickness Limitations

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Title: Construction Loads and Serviceability Requirements: Deflection Control, Span/Thickness Limitations

Author(s): D. Kaminetzky and P. C. Stivaros

Publication: Special Publication

Volume: 210

Issue:

Appears on pages(s): 1-18

Keywords: code provisions; concrete slabs; cracking; deflection control; long-term deflection; reinforced concrete; serviceability

Date: 2/1/2003

Abstract:
Throughout the history of concrete construction, numerous construction failures have occurred involving excessive deflections and cracking of the completed structure. This paper presents two building construction cases where concrete slabs developed extensive cracking and excessive deflections soon after the slab construction and formwork removal. The effects of the shoring-reshoring operations, the rate of concrete strength development, as well as the effects of design details on the slab cracking and deflections, are investigated. The ACI 318 requirements of minimum thickness and deflection control are applied to both construction cases, and the adequacy of these code requirements is discussed. Based on the findings of this work it was concluded that the ACI 318 long term creep and shrinkage deflection calculation method does not adequately account for the early-age high construction loads.