Analysis of Vertical Load Distribution in Shoring and Slab Systems of Multistory Concrete Structures under Construction.

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 to analyze loads in a concrete structure under construction, spreadsheet models have been developed which distribute load inputs chosen by the engineer. The models determine the vertical loads resisted by the following shoring systems: one set of shores with either two or three sets of reshores; two sets of shores with either one or two sets of reshores; or three sets of 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, D. Slab liftoff was then analyzed to prevent improper loading conditions during the construction cycle of multistory concrete buildings. The results of the models were validated by comparison with previously published shoring analysis. Lastly, a sensitivity analysis is performed to compare the loads supported by individual slabs and sets of shores in each model during the placement of upper floors.