Spreadsheet Analysis of Load Distribution in Shoring and Reshoring Systems

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Title: Spreadsheet Analysis of Load Distribution in Shoring and Reshoring Systems

Author(s): Michael P. McGurl and David W. Johnston

Publication: Special Publication

Volume: 285

Issue:

Appears on pages(s): 1-20

Keywords: buildings, concrete, construction, formwork, reshoring, shoring

Date: 5/1/2012

Abstract:
Analysis of the construction load distribution during construction of multistory concrete buildings is critical for both construction safety and economy. Recent reduction of load factors used in design of the permanent structure has resulted in less strength availability in the construction stage and need for tools to better support shoring and reshoring analysis. Using the traditional simplified method presented in ACI SP-4 for concrete structures under construction, spreadsheet models have been developed which analyze the distribution of loads based on inputs chosen by the engineer. The models determine the vertical loads resisted by temporary construction systems and the slabs with various combinations of levels of shores and reshores and with mechanical drophead shores. Analysis can be performed using either unfactored or factored loads and using either actual uniform loads or loads expressed as a proportion of slab dead load. The results of the models were validated by comparison with previously published shoring and reshoring analyses. Lastly, a comparison of the loads supported by the individual slabs and the levels of shores in each model during the placement of upper floors is made.