Eccentrically Prestressed Box Girders Under Combined Bending and Torsion


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Title: Eccentrically Prestressed Box Girders Under Combined Bending and Torsion

Author(s): Barrington deV. Batchelor and W. Douglas McEwen

Publication: Journal Proceedings

Volume: 74

Issue: 4

Appears on pages(s): 156-162

Keywords: beams (supports) ; bending; bending moments;box beams; cracking (fracturing); failure; girders; prestressed concrete: prestressing steels; pretensioning; structural analysis; torsion; torsion tests.

Date: 4/1/1977

An investigation of bending-torsion interaction in eccentrically prertressed concrete box girders is reported. The ten specimens tested were under-reinforced in the longitudinal and transverse directions, and were prestressed initially so that extreme fiber stresses were up to the limits allowed in practice. The only intentional variable in the study was moment-torque ratio which was varied over the range of zero to infinity. Bending-torsion interaction at first cracking was closely predicted by a parabolic equation proposed by Cowan for sections without transverse reinforcement. Interaction at ultimate conditions conformed closely to parabolic relationships, proposed by other investigators, for use with under-reinforced rectangular sections. However, certain redefinitions of terms are make the existing interaction equations applicable to sections with high eccentric prestress. A procedure, incorporating these modifications, is presented for developing interaction diagrams for girders of the type studied.