Validity of Certain Assumptions in the Mechanics of Prestressed Concrete

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Title: Validity of Certain Assumptions in the Mechanics of Prestressed Concrete

Author(s): Grover L. Rogers

Publication: Journal Proceedings

Volume: 50

Issue: 12

Appears on pages(s): 317-330

Keywords: no keywords

Date: 12/1/1953

Abstract:
Validity of certain assumptions of structural mechanics applicable to the analysis of prestressed concrete structures is discussed. Results of field tests conducted in France indicate that the calculated load causing the first tensile crack (based on ordinary elasticity theory) in a prestressed concrete slab may be only one-fifth to one-sixth the actual load. This difference has been accredited to the inapplicability of the assumptions of isotropy, homo-geneity, and elasticity as employed in the theory of elasticity to prestressed concrete slabs. As a result of these tests new concepts have been suggested as a possible basis for a more realistic theory. Analytical and experimental results of a test conducted on a laboratory model of a slab prestressed in two directions show that the assumptions and use of the theory of elasticity are indeed adequate. The load causing the first tensile crack was found to be within a few percent of the load predicted using elastic theory. Such agreement indicates that the discrepancies between theory and practice must be attributed to other causes rather than inherent errors in the theory-of elasticity. While the reasons advanced for the discrepancies in the French tests are not valid, the fact they did occur must not be overlooked.