Saturday, November 12, 2016

Covered Bridges October 20, 2016

Copyright © 2016       John F. Oyler

October 20, 2016

Covered Bridges

I suspect most of us are fans of covered bridges; being a Civil Engineer I have no choice. Last month I decided to take advantage of the Washington and Greene Counties’ Covered Bridge

Festival and visit a couple of bridges I had not seen before – Krepps and McClurg.  Both bridges are in western Washington County and are of similar size.

Krepps Bridge is located about five miles north of Hickory, on Covered Bridge Road, very close to its intersection with Waterdam Road (Legislative Route 4018). It is still in use, carrying Covered Bridge Road over Cherry Creek, a small tributary of Raccoon Creek.  The bridge is about twenty four feet long and thirteen or fourteen feet wide.

The McClurg Bridge is located in Hanover Township Park, on the south side of State Route 4004, about a mile west of Florence. Unlike Krepps, it is a museum piece, spanning a dry ravine and used only by people on foot using the park. Both bridges are painted barn red and have window openings on each side – two for Krepps and four for McClurg. McClurg’s original location was northwest of the hamlet of Paris, spanning King’s Creek.  It was moved to the Park in 1987.

Both bridges are of a type I would designate as a braced King Post truss. The deck is constructed of planks supported by transverse floor beams at midspan and quarterpoints. These beams are hung from the trusses by rugged wrought iron rods. The trusses consist of heavy vertical posts at midspan intersected eight or ten feet above the deck level by massive sloping diagonal members.

To visualize a King Post truss, imagine a huge arrow pointed upward with its shaft being the vertical post at the mid-span of the bridge and its wings being the large diagonal members sloping down to the piers at each end. Then add a horizontal member at deck level, connecting the bottom ends of the diagonals.

It is very easy for a Civil Engineer to stand at the middle of the bridge and imagine the way a heavy load at that point is transferred to the abutments at either end of the bridge. The weight of a hay wagon, for example, in the middle of the bridge is transferred laterally through the deck’s floor beam to the bottom of the King Post, which then acts as a hanger. Because the top of the King Post is restrained by the diagonals, the load is transferred to them; they in turn, transfer it through a compressive thrust to the abutments.

The horizontal member then keeps the bottoms of the diagonals from sliding outward. To support the floor beams at each quarter-point another wrought iron rod is suspended from the diagonal at mid-height, and a short diagonal leading to the bottom of the King Post added as a brace.

Simple, but remarkably effective, the King Post truss is the ancestor of a large family of truss types, each conceived to achieve a specific goal. We engineers today have the tools and technology to analyze these classic bridges and can only marvel at the ingenuity and craftsmanship of the people who built them two centuries ago.

The covered bridges that have survived have outlasted many of the more modern ones that followed them. We are happy that Krepps is still going to work every day and hope that McClurg is enjoying her well-deserved retirement. We suspect she winks her eye and grins every time a pair of lovebirds pass through her and steal a kiss when no one is looking.

Getting to Krepps was easy, because the directions were well presented.  McClurg was a different story. The directions on the Washington County Tourism website were vague and confusing.  Eventually I searched for Hanover Township and sorted out where I should go.

Both festivals were fun. The one at Krepps was in a field adjacent to the bridge. I didn’t care much for the music there, but did invest in a decorated coin purse at one booth and a funnel cake at another. Praising the funnel cake is probably inappropriate – was there ever a funnel cake that a Pennsylvania Dutchman didn’t like?

The McClurg festival was in an established park which already had all the necessary infrastructure. I did like the music there, especially when the five piece band performed a very respectable “Margaritaville”. At this point I was hoping to find an Amish booth and purchase some baked goods. Bad news was the absence of an Amish booth; good news was an excellent Greek bakery booth. I ended up with olive bread, baklava, spanakopita, and pepperoni rolls; all of which were good.

I was surprised to learn recently that pepperoni rolls originated in West Virginia as a major component in the coal miner’s lunch bucket and that their popularity is still limited to the Tri-state area. My wife used to make them for our kids’ school lunches; I assumed they were a universal food.

All told it was an enjoyable afternoon. I was originally disappointed that the bridges were so short, but since then I have appreciated the advantage that opportunity gave me to inspect true King Post trusses. We are fortunate these historic artifacts have survived.


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