Wednesday, July 16, 2014

2014 Northeast Tour (Part 2)

For part 1, click here.

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From Woodstock we traveled south on Rt. 106, to the county of West Windsor, where a few more covered bridges were to be found. The first one we came across is called Best Bridge, a fairly modest affair:


This was built in 1889 and spans 37 feet over Mill Brook.

The bridge is a simple arched truss, placed atop carrier beams and employing tie rods to hold up the roadbed:


Underneath the deck, there is only scissor bracing:


Here's the foot of the arch meeting the carrier - double-notched and reinforced with two bolted straps, and a large wedge or two at the back to tighten things up:


A short distance away was Bowers Bridge, originally constructed in 1884~86, however a victim also of Hurricane Irene.

The storm waters washed the bridge 200 yards (182m) downstream:


(image from FEMA)

It's now rebuilt and back in place:


The newly rebuilt bridge incorporates some of the original pieces, notably the deck and most of the arched chords, and sits 18" higher.

Some online bridge sites give the construction date for the bridge as being 1919, but this cannot be correct, given some of the graffiti:


Simple framing for the common rafter roof look like a lot of barn framing, and support for the deck is by way of a tied arch like the Best Bridge just down the road:


The under deck with scissor bracing:


The joint between the foot of the arch and the sill piece:


We continued on south, entering the county of Weathersfield, where we came across the town of Downers and their bridge, a Town lattice truss spanning 120':


Constructed in 1840 by James F. Tasker, and restored in 1975~6:


Like the Middle Bridge in Woodstock, this Town lattice has two runs of top chords:
 

The lower chord supports an additional set of braces which meet at the ridge:
 

The braces make for a much stronger tie between the roof and the walls, and stiffen the structure considerably. I tend to associate them to old French framing practice. I well remember an engineer's article in an old issue of the Journal Timber Framing, where they found the addition of such braces to the standard knee-braced shed building, a standard Timber Framing Guild class project, finally made the building adequately stiff.

A view out of the window of Black River:


Next on the tour, further south in Springfield County, was Bartonsville Bridge, yet another bridge which suffered considerable damage from the Hurricane:



The good news is that this bridge, originally constructed in 1870, has been rebuilt and reset into position on improved foundations:


This is a Town lattice truss, spanning 151' and with single run of top chords:


I found the attachment of the braces to the side of the lattice a little unusual. Also new to me were the angled braces between the truss lattice and the walls, just visible in the above photo. They are so acutely angled I'm not sure what they really add in terms of strength or stiffness. It looks like the wall cladding kind of hangs on the rest of the structure, like a jacket

A view of the juncture between wall and roof framing:


A very well braced bridge with lots of galvanized bolts. Gotta wonder if the consulting engineer wasn't a bit twitchy about using treenails on the lattice instead of bolts:


Under the deck we see a combination of scissor bracing and tie rods:


Another view:


Nearby was the Worral Bridge, a Town lattice constructed in 1868 by Sanford Granger:


Love the sign:


Another bridge where the braces, at least some of them, terminate on the side of the truss web:


A view of the roof structure:


One last bridge, which no longer sits across a river, but has been relocated over a drainage ditch as a tourist attraction, the 'Victorian Village' covered Bridge:


I include this one as it is an example of a more archaic framing style, using a modified kingpost with straining beams:


Simple roof framing with a few added braces atop the crossbeams:


Stiffening a rafter here and there will make for an undulating roof plane over time. It would have made more sense to place a purlin and brace against that, but well, it is what it is. It's kind of a shortened and thrown-together mish-mash of an old bridge formerly called Depot Bridge (1872), incorporating other bridge parts, and some metal reinforcement underneath. Cars can still drive over it though.

That's all the bridges for this year. There are plenty more to be seen however so look for another post in this intermittent series in the next year or so. Thanks for visiting!!

7 comments:

  1. Chris, did you have the locations of these bridges before hand or just "wandered around" and came across them. Sounds and looks like a nice road trip and a nice break from the "gate" project.

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    Replies
    1. Joe,

      thanks for the question. Actually i made no plan to look at bridges on this trip. Our New England road atlas by Jimapco happens to have little covered bridge symbols on the pages wherever the bridges are - or were. in some cases we couldn't locate the bridge, and in others the bridge appeared to have been washed away and not rebuilt. But it gave us a way of planning our route back so that we would pass by several bridges and check them out. That was the only rhyme/reason to have seen the bridges we saw - they happened to be on our route and the map let us know where they were.

      Both my wife and I still like 'old-fashioned' maps, and don't use GPS in our cars. I've always liked maps - I enjoy just looking at them.

      ~C

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  2. You need to get back home and finish up your Square Deals!!!! :) Lovely pics. Hope you're having a great time.

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    Replies
    1. tdok,

      nope, taking a couple of days off with my wife was the perfect thing to do. Projects await of course...

      ~C

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  3. More bridges please. How about a little history about the development of wooden bridge design along with appropriate pictures of course... (hey, it never hurts to ask.)

    I find the lattice design quite complex. Are there early variants where the kinks were worked out, because the examples here seem amazingly similar.

    Interesting blog as always.

    -Harlan Barnhart

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  4. ... make for an undulating roof plane over time." It's unclear what you mean by stiffening a rafter in the last example. My experience is that the lack of a ridge beam is what causes roof lines to develop that wave effect.

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    Replies
    1. Potomacker,

      thanks for the comment. I was referring to the single inclined brace atop the tie beam in that picture, which connects to the side of a rafter above.

      The lack of a ridge is not what causes common rafter roofs to develop a wave effect - sagging really. The problem relates to two things:

      1) foundations are often not properly compacted and over time subsidence occurs which causes the mudsill to be poorly supported in areas. The means the walls above these areas will settle downward
      2) the common rafters tend to push the wall plates outward, and roll the wall plate outward. If there is insufficient means provided to keep the walls from being pushed outward (i.e., tie beams or cables), the walls become pushed out horizontally at the plate level. This occurs less at the end walls as there are tie beams in those locations. The walls are bulged out the most in the middle of the wall run typically.

      The combination of the wall plates being pushed outward and the walls settling due to uneven plate support causes the roof to develop a sag in the middle. The addition of a ridge beam alone would do little to correct this issue. A thick ridge beam, in addition, will shrink and this can cause the ridgeline to become uneven/sagged as the rafters settle in and down along the ridge.

      ~C

      Delete

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