Transverse diaphragms and unbonded CFRP post-tensioning in box-beam bridges

Abstract

This paper presents the effects of the number of transverse diaphragms and the level of transverse post-tensioning forces using unbonded carbon-fiber-reinforced-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-by-side 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 post-tensioning 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 post-tensioning 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.