Transverse diaphragms and unbonded CFRP posttensioning in box-beam bridges

This paper presents the effects of the number of transverse diaphragms and the level of transverse post-tensioning forces using unbonded carbon-fiberreinforced-polymer (CFRP) strands on the behavior of side-by-side box-beam bridges. An experimental program, consisting of load- and strain-distribution tests, was conducted on a half-scale, 30-deg-skew, side-byside box-beam bridge model. The bridge model was tested under three different phases: uncracked deck slab, cracked deck slab, and replaced beam. An ultimate-load test was conducted to evaluate the response of the unbonded transverse post-tensioning arrangement up to failure of the bridge model. The experimental results show that increasing the level of transverse post-tensioning forces generally improved the flexural behavior of the bridge model. Moreover, the different arrangements of the transverse posttensioning forces had insignificant influence on the transverse strains developed in the region between the diaphragms. From the results of the ultimate-load test, it was evident that the unbonded transverse posttensioning arrangement coupled with the deck slab uniformly distributed the applied eccentric load in the transverse direction until complete flexural failure of the bridge model occurred.