Torsional Strenth of Prestressed Concrete Members

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Title: Torsional Strenth of Prestressed Concrete Members

Author(s): Paul Zia

Publication: Journal Proceedings

Volume: 57

Issue: 4

Appears on pages(s): 1337-1360

Keywords: none

Date: 4/1/1961

Abstract:
Reported are the results of torsional tests of 68 pre- tensioned and plain concrete members consisting of rectangular, T- and l-sections. Some of the specimens also contained web reinforcement in the form of ties. For the rectangular and T-sections, the test results com- pare closely with the predicted stren th by a modification of Cowan’s failure criterion. Actor 8ing to this criterion, which is noted as a close approximation of Mohr’s failure theory, the optimum uniform prestress is 70 percent of the concrete cylinder strength. Corresponding to this optimum value, the torsional strength of a member is increased to 281 percent of that of the similar plain concrete member if the cylinder strength is 6000 psi. For the l-sections, the test results exceed considerably the predicted strength. Explanation of this discrepancy is offered OS being the consequence of stress redistribu- tion after the initial cracking. However, it is suggested that the usable sirength of such a section be token OS the cracking moment, since the crocks due to torsion remain open on unloading and thus permanently damage the concrete member.