Flexural response of CFRP prestressed concrete box beams for highway bridges

This paper presents an experimental and analytical investigation of the flexural response of box beams reinforced and prestressed using carbon fiber reinforced polymer (CFRP) tendons. Two one-third scale box beams were prestressed using seven bonded pretensioning tendons and six unbonded post-tensioning tendons. A third beam was prestressed with seven bonded pretensioning tendons and six non-prestressed unbonded post-tensioning tendons. Beams were reinforced with carbon fiber composite cable stirrups and tested to failure. A computer program was developed to predict deflection, strain, and post-tensioning forces at various loads. A parametric analysis examined the effects of the level of pretensioning and post-tensioning forces on the overall flexural response. Results showed that the beam prestressed using both pretensioning and unbonded post-tensioning tendons had a 26 percent higher ultimate load capacity and 36 percent lower energy ratio than the beam with non-prestressed unbonded post-tensioning tendons. Levels of initial pretensioning and post-tensioning forces significantly affect the flexural response and beam failure mode.