Wards Ferry Road Bridge

This bridge is slated for replacement in 2017 or 2018 by a single span precast/pre-stressed concrete two lane bridge or a pre-cast earthen filled arch bridge, per Tuolumne County's web site: http://ca-tuolumnecounty.civicplus.com/DocumentCenter/View/1.... I guess yet another picturesque old bridge is about to be replaced by a characterless modern structure in the name of progress.

This bridge has what seems to me to be a most unusual method of connecting the floor beam to the truss web, where the floor beam is framed inside the built-up vertical box beam: http://www.flickr.com/photos/denisephotos/7066830907/

This bridge could have been built in 1915. I have a number of pin-connected pony trusses listed from 1913 and 1914. 1915 would be rare, but not impossible to suppose.

Feel free to correct if I am wrong, but it is my understanding that Warren trusses feature diagonals whose members alternate from Compression to Tension across the truss web.

This pin connected truss bridge features diagonal members that are all eyebars (tension members). No diagonal members on this truss are capable of dealing with compression forces. In addition, note that the counters on this bridge, true to the typical form, are of lighter construction than the diagonals. I would further suspect that these counters may have turnbuckles on them, something that counters have but diagonal members don't. This bridge thus appears to be a Pratt truss.

In respect to the bridge in Oregon, the Beaver Creek Bridge, I would argue it could be either a Pratt with counters or a double-intersection Warren. The diagonal members on that bridge seem capable of addressing compressive forces. I wonder if an engineering analysis could determine whether the diagonal members are all functioning as tension members with the counters also being tension members or if an alternation between tension and compression is found in the members, this would suggest a warren.

In respect to verticals, I do not see why vertical members would disqualify a bridge from being a Double-Intersection Warren. A majority of single-intersection Warren truss bridges include vertical members, logic would suggest that double-intersection Warrens could also include verticals.

I also know of no requirement that a double-warren must be a through truss.

It is always a pleasure to engage in discussion with my fellow Pontist friends of Bridgehunter Nation.

I consider all of you as my extended family and wish you and yours a safe and happy Thanksgiving!

Yes, Happy Thanksgiving everybody. I may spend Black Friday Bridgehunting! Will have to see...

I totally agree Craig. Great discussion leads to great knowledge. It would also appear that my past ODOT brothers have lead me astray in identifying this configuration of truss. I must concede to the Pratt pony truss configuration.

I would also like to wish a Happy Thanksgiving to all the Bridgehunter community.

This discussion and exchange expresses the very best of bridgehunter.com. Happy Thanksgiving to pontist everywhere.

1915 does sound a bit late for this one.

Not impossible...but I would liken it for a ca.1900 span.

Pinned Pratt pony-4 panels with counters in the 2 center panels.

No doubt in my mind...we have several of them here in the Hoosier state.

I totally buy your disagreement with the HAER report for the double-intersection Warren pony truss.

Had there been no verticals on either one of these structures, the double-intersection Warren makes sense. The vertical members make all the difference in this configuration.

Sure, that makes sense. I am going to have to respectfully disagree with HAER on the bridge in Oregon. My thoughts is the counters on the Oregon example make the bridge a Pratt, but if someone has a different idea then please post it here.

http://www.bridgehunter.com/or/columbia/beaver-creek/

This bridge located in Columbia County, Oregon is where I came up with the double-intersection Warren pony truss. I was just taking what the HAER Report states.

MG

There is a possibility that this bridge could be a few years older than 1915. It is pin-connected and by 1915, pinned connections had generally been replaced by riveted gusset plates. Pony trusses are a little harder to estimate for age because they lack portal bracing and sometimes other features. My guess is that this bridge could have been built between 1900-1910, unless pinned joints were used after that in California.

I would call this a four panel Pratt pony truss myself. I can't think of a double-intersectional Warren pony truss right now, but here is what a double-intersectional Warren through truss would look like. http://bridgehunter.com/ks/franklin/tauy-creek/

I am sure one of the truss experts can correct me if I am wrong, but I believe we call this a double-intersection Warren pony truss. I can not speak for California but this would be an extremely rare find in Oregon.

Interesting little pony truss, just what truss design is this?