Flexural behavior of continuous steel girder with external post-tensioning and section enhancement

The internal support of a continuous bridge is known as one of the weakest points of the structure because it is governed by a negative moment. Stress due to the negative moment causes the lower part of the section around the internal support to resist compression and to be structurally weak, while the lower part of a section in the zone of the positive moment is subjected to tension. By improving the geometrical property of the section, this stress can be reduced. Therefore, attaching an extra section to the base can strengthen a section that is governed by a negative moment. This strengthening method can be termed the ‘section-depth increment’. In addition, a prestressing technique can be jointly applied together with the section-depth increment, using the attached section as an anchor. In this study, an experiment was conducted on the application of a section-depth increment and external prestressing technique. The effect of the applied strengthening methods was examined in terms of flexural behaviors. The results of the experiment showed that the flexural capacity of the specimens was improved over 30% when strengthened with the section-depth increment method.