Analysis of Shoring Loads and Slab Capacity for Multistory Concrete Construction

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Title: Analysis of Shoring Loads and Slab Capacity for Multistory Concrete Construction

Author(s): John L. Gross and H. S. Lew

Publication: Special Publication

Volume: 90

Issue:

Appears on pages(s): 109-130

Keywords: computer programs; concrete construction; concrete slabs; form removal; formwork (construction); loads (forces); microcomputers; multistory buildings; reinforced concrete; safety; shoring; structural analysis; General

Date: 4/1/1986

Abstract:
This paper describes a microcomputer-based program which can be used to assist the contractor in evaluating the safety and economy of alternate construction schemes in cast-in-place multistory concrete building construction. The program, developed at the National Bureau of Standards, assumes that the slabs are supported by evenly distributed, compressible shores or reshores. Forces on the slabs are computed by assuming that superimposed construction loads are distributed to the shoring system and interconnected floors in proportion to their relative stiffnesses. The method takes into account both the stiffness of shores and reshores and any precompression in the reshores. Slab capacity is computed from a maturity-based model of concrete strength prediction. The computed slab loads are compared with the slab capacities to determine whether the load on any slab exceeds the capacity of that slab for any stage of construction. By varying the number of shored and reshored stories, the precompression of reshores, and rate of construction, the optimum casting schedule can be determined. Examples are given which illustrate how this program can be used to assist the contractor in determining a safe casting schedule and to guide the contractor in formwork removal.