Behavior of prestressed concrete box-beam bridges using CFRP tendons

This paper presents the results of an experimental and analytical study of the flexural response of concrete box beams prestressed with carbon fiber reinforced polymer (CFRP) tendons Diversified Composites Inc. (DCI) for three highway bridge models. Each bridge model comprises two precast concrete box beams pretensioned using DCI tendons. In one of the bridge models, the box beams were also prestressed using 12 unbonded DCI post-tensioning tendons. In the second bridge model, the box beams were not provided with post-tensioning tendons. The third bridge model comprised box beams provided with 12 unbonded tendons without any force. This study consisted of predicting parameters such as transfer lengths of DCI tendons, ultimate loads, deflections, post-tensioning forces, strains, and energy ratios. This paper also presents a comparison of experimental and analytical results. It was observed that the measured transfer lengths, of DCI tendons ranged from 25 to 32 times the nominal tendon diameter. The bridge model comprising Z box beams prestressed using both pretensioning and unbonded post-tensioning tendons resulted in higher load capacity and lower ductility compared with the other two bridge models. The close agreement between experimental and analytical values signifies the accuracy of a strain-controlled approach in analyzing CFRP box-beam bridge models.