Exprimental Investigation on the Behavior of Sigmentalbox Girder Bridges With External Prestressing Under Combined Shear, Moment and Torsion

Abstract

Currently, segmental box girder bridges with external prestressing is widely used in construction all over the world. This paper presents experimental test results on five specimens represents a box girder bridges with external prestressing taken with one-tenth scale. The specimens were simulated to the internal negative moment zone bounded by contra flexure point as cantilever specimen. All specimens are segmental beams with dry-keyed joints and they were tested under; bending, shear and torsion. Applied load eccentricity which causing torsion variation and tendon prestressing force level are the two main studied parameters. The behavior of the beams was evaluated in terms of; load open critical joint, cracking load, ultimate load, deformations such as deflections, twist angle and joints opening width as well as, strains of external tendons and internal steel. Also, behavior of the specimen including modes of failure, cracks propagation history and some critical values are also discussed. Some important remarks also are presented. The experimental results showed that, the existing of torsion has significant effect on the beams cracking behavior, deformed shape, mode of failure, and has slight effect on increasing the prestressing tendon stress at eccentric applied load side more than the side far from the applied load. Also, increasing effective prestressing force level has a significant effect to delay cracking due to shear stresses, and improve the beam deformation against flexure and torsion. Also, it has slight effect to reduce the difference between tendon stress at every side.