ECCENTRICALLY PRESTRESSED BOX GIRDERS UNDER COMBINED BENDING AND TORSION

An investigation of bending-torsion interaction in eccentrically prestressed concrete box girders is reported. The ten specimens tested were underreinforced 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 H. J. Cowan for sections without transverse reinforcement. A procedure is presented for developing interaction diagrams for girders of the type studied.