Use of post-tensioning in strengthening steel girder - Slab type bridges

The need to upgrade a large number of understrength bridges in the United States has been well documented in the literature. Through several research projects, which involved testing of strengthening schemes on scale model bridges in the laboratory as well as the testing of strengthening systems on existing bridges, the concept of strengthening simple span and continuous-span bridges by external post-tensioning has been developed. A posttensioning strengthening design manual for simple span bridges has been developed for use by practicing engineers. A similar manual and spreadsheet for continuous-span bridges has also been developed. In addition to the post-tensioning system, the authors have developed superimposed trusses for strengthening the negative moment regions of continuous steel-stringer bridges. This paper will briefly review these strengthening procedures which have been successfully employed in the field.