Flexural behavior of externally prestressed continuous steel-concrete composite beams

To investigate the flexural behavior of continuous externally prestressed steel-concrete composite (EPSCC) beams, flexural tests were conducted on two two-span continuous beams with a total length of 9.8 m. The test parameter focused on the number of deviators in each span. With the aid of detailed measurement of deviator displacement, slip distribution on the steel-slab interface and strain along shear connectors, the shear mechanism of headed studs and the second-order effect in continuous EPSCC beams were evaluated. The test results indi-cated that both beams underwent concrete cracking over their interior supports, followed by the formation of a plastic hinge in the hogging moment zone, the subsequent formation of a plastic hinge in the sagging moment zone, and ultimately the crushing of concrete slabs in the sagging moment zone. Prior to failure, full plasticity was developed at both the mid-span section and interior support section of each beam. The local moment acting on the shear studs reached its maximum hogging values at the shank root, while its maximum sagging value was attained at approximately the mid-height of the shank. Due to the second-order effect, the removal of deviators at midspans resulted in a 7.1% decrease in the sagging moment of the beam. At the ultimate limit state, the measured degree of moment redistribution values for hogging moment ranged between 52% and 58%, which were higher than the specified limits in current design guidelines. The predictions of the ultimate hogging and sagging moment calculated from plastic theory were consistent with experimental results.