The interchange ramp bridge in study is a continuous pre-stressed concrete box beam bridge. A comparative study of calculated rupture conditions of beam structure under different assumptions and the practically tested rupture conditions illustrates that the side-span beam structure seriously lacks of internal existing prestressing force and fails to meet the regulation requirements, owing to which it needs reinforcement. For the purpose of better visual effects, decisions have been made to adopt external prestressting approach inside the box girder. Numerical analysis shows after reinforcement the structural carrying capacity and partial stress-strain both can meet regulation requirements. The comparison of the static loading tests before and after reinforcement further indicates that the employment of external prestressing approach notably enhances the overall stiffness of the beams and fulfills the design purpose of reinforcement of the beam structures.
