Yes, deck stringers and deck surface are frequently not original, and their replacement is not considered to reduce the historic integrity of the bridge because it is considered part of routine maintainance and is often done many times over the life of a properly maintained bridge. Floorbeams are a different story. As a part of the actual superstructure, their replacement represents a loss of historic integrity. I would comment that on a percentage basis, most truss bridges retain original floorbeams. Usually the reason for them having original floorbeams is due to neglect rather than preservation. This is unfortunate, since I would like to see original floorbeams retained during preservation work, but often they are discarded and replaced with modern wide flange beams. At the very least, original floorbeams could be replaced with new replicas instead of modern substitutes.
Floor systems were replaced often. While the truss itself often remains intact, the deck and floorbeams and stringers are rarely original.
Yes, this form of retrofit shows up in many places. Have seen examples in Michigan, New York, Maryland, and New Jersey as well as Pennsylvania.
Placement of stringers underneath floorbeams is generally considered a less visually obtrusive method if a retrofit or structural bypass to render the trusses decorative is determined to be the only viable preservation solution.
Retrofit can sometimes be better than rehabilitation because it may be possible to add stringers or the arch and thus not have to remove or replace original bridge material to provide loading requirements. However in most cases I have seen these arches added, I have also found the entire flooring system replaced, representing loss of original bridge material, so in that respect I fail to see any benefit.
There are several of these across PA. The retrofitted arch was championed by now-retired Bucknell University engineering professor Dr. Jai Kim.
What a horrible mess! I’d be ashamed to admit I had anything to do with this so called reconstruction.
I have to hold my ground on this one......but I will soften my tone just a bit. I feel like it destroys the integrity of the bridge to weave a new structure into it. It is hard to enjoy the beauty of the original trusses when your attention is drawn to a massive arch. I was the inspector on an 1887 wrought iron bridge rehabilitation. The bridge was restored in-kind with minimal changes and now carries a 15 ton load limit. The right engineering firm would have approached the rehab differently, and with better results.
However, I guess the fact that PennDOT even kept a historic bridge should account for something.
Opposing view, I see this not as a hack job but rather an innovative method to not only preserve in place, but to re-open for use an historic bridge. Here is a link to the repair company. http://www.highsteel.com/project_gallery/bridges/GerloffRoad.cfm
This is about as bad of a HACK job on an otherwise unique structure that I have seen. What a waste on a span that could have been restored the right way.
This appears to have been a through truss that PennDOT or the Twp. slapped some arches on to keep it standing. My bet is that truss is no longer holding anything but itself.
I've seen an example of this somewhere, just gotta find it...