Reconstruction of Windsor Bridge piers

Abstract

The Windsor Bridge provides a two-lane highway crossing of the Susquehanna River in Broome County, New York. The structure comprises three 62.5-m (205-ft) simple-span through trusses supported by reinforced concrete abutments and solid-shaft piers. Having been built in 1935, it required rehabilitation in the early 1980s. The major effort included a deck replacement and complete structure repainting. What was expected to be relatively minor surface restoration of the foundation units became much more involved and complex. A coring program was initiated for predictions of the volume to be restored. The cores were petrographically examined and found to exhibit evidence of freeze-thaw damage and alkali-silica reactivity of the aggregate. The shafts, which were 2.13-m (7 ft) thick, were found to be delaminated from the freeze-thaw damage to depths of up to 610 mm (24 in.). An intensive evaluation of alternatives concluded that the most appropriate solution for this situation was to encapsulate the pier shaft with a concrete shell 305 mm (12 in.) thick with through-shaft posttensioning to retain the deteriorated existing concrete. This innovative solution is believed to be extremely unusual, if not unique, in the United States. Many unusual design-related issues were encountered while developing the plans for restoration. The background of the initial evaluation, development of alternatives, design philosophies, and general issues associated with the construction are presented. Thermosensor findings are also included, which yielded interesting and unexpected results. The knowledge gained from this project can be useful to other consultants and bridge owners.