Monday, March 28, 2005

A New Metal Truss Bridge Can Look Good Too!

A picturesque new metal truss bridge Posted by Hello

I ran across this bridge when looking for an old bridge that was in the area. Sure looks better than a slab of concrete.

Sunday, March 27, 2005

Some Basic Truss Terminology

When is a pony not a horse? Posted by Hello

Some terminology has creeped in that may be foreign to some. A Pony truss refers to trusswork that is on each side of the roadway but has no interconnection other than the roadway itself. A Through Truss has overhead members that cross the roadway and add additional regidity to the trusswork.

One way to remember is that you drive through a Through Truss. I don't know how the pony designation originated.

Subtle Truss Differences

Brown Road Bridge, Delaware Ohio. Posted by Hello

This is a Pratt Through Truss design. Notice it has a vertical member connecting to the top of the first (sloped) member. This is the more usual Pratt truss design. This member is reduced to a thin "tension rod" in the Stockwell Road Bridge.

Saturday, March 26, 2005

Bridge About to be Bypassed.

Beginning of the end for the Stockwell Road Bridge. Posted by Hello

Today I visited the Stockwell bridge again and the (de) construction has started as shown in this four-frame panoramic view. A new bridge is going in the forground bypassing the old bridge.

I hadn't appreciated before that this bridge is an unusual Pratt Half-Hip Through Truss design. I've only seen Pony Half-Hips before (see earlier post).

Thursday, March 24, 2005

Going, going gone!

Stockwell Road Bridge Posted by Hello

This example of a Pratt Through Truss bridge was built late 19th century. It is located in Delaware Ohio but is scheduled for replacement this year. A similar bridge just down the creek has already been replaced. I spoke to the adjacent landowner who was sad to see it go after living next to it all her life.

An abandoned iron bridge

Mill Road Bridge Posted by Hello

This bridge is on an abondoned road in Knox County, Ohio. It is gradually falling apart even though its recognized by the National Registry of Historic Places and is documented by the Historic American Engineering Record (HAER). See the links to read about it on HAER. The truss design is called a bowstring.

It took me 4 trips to locate this bridge as the maps I was using had it 4-5 miles from the actual location but that's part of the fun!

Note added 4-27-2005: Some good news! This bridge is apparently slated for rehabilitation by the county and is to be dismantled and moved to a pathway in Mount Vernon, Ohio.

Monday, March 21, 2005

A Common Metal Truss Bridge.

The ubiquitous Warren Pony Truss Bridge Posted by Hello

This style of truss bridge is still a common sight on the backroads of Ohio. The design is old but this bridge is less than five years old.

Pratt Half-Hip Truss Bridge.

Private Driveway Bridge Posted by Hello

This little bridge is on a private driveway over Rattlesnake Creek in Delaware County, Ohio. Don't know anything about its history but it looks early 20th century. The sign says load limit 1 ton. This could be a joke!

Some Replacement Bridges are Attractive!

The New Beach Road Bridge Posted by Hello

This is the new Beach Road bridge in Franklin County Ohio that replaced the old Westerville truss bridge. This cable stay bridge is an attractive alternative to the boring metal I-Beam or concrete stringer bridges.

Friday, March 18, 2005

How Do I Find the Bridges?

Bridge locations in Ohio Posted by Hello

If you want to visit some of the remaining bridges near you how do you go about finding them? Well every state is required by the federal government to maintain an inventory of historic bridges. Google the Internet for the website of the Department of Transportation (DOT) for your state and if you’re lucky you will run across the listing. In Ohio, for example, the 2005 inventory of Ohio historic bridges can be found at: http://www.dot.state.oh.us/oes/bridge_status.htm

For Ohio and most states there are also printed materials that provide this information, for example: The Second Ohio Historic Bridge Inventory, Evaluation and Preservation Plan, Ohio DOT 1990; and the Ohio Historical Bridge Guide, Bill Helsel, David Simmons and Miriam Wood. Ohio Historical Bridge Association. Seventh Ed 1999/2000. However the printed documentation is usually dated. It can take some perseverance to get accurate information. That is why I am compiling a list for my area (Ohio). Check out my Website (see Links).

Thursday, March 17, 2005

The Fate of Most Metal Truss Bridges

Fosnaugh Bridge Location Posted by Hello

This is the fate of most old metal truss bridges. I find nothing aesthetically pleasing about an I-Beam supported roadway. The only visible structure is the DOT approved guardrail.

However, the original bridge was inadequate to support modern traffic loads and was awaiting some idiot in a fully loaded cement truck to end its existence. About all we can hope is for the best examples to be bypassed or moved and preserved on a bikeway. The next generation will not see many of these bridges in the “wild”. So see them now!

Design your own truss.

Calculation of forces in a truss. Posted by Hello

The forces (red = tension, blue = compression) in a simple truss with a load of 50 at the center node are shown in the figure. There is a neat web site that lets you design and calculate the forces in trusses that you come up with: Bridge Designer

There are some limitations in the program that restrict the designs but its fun to play with. Early bridge builders did not have the benefit of such design tools and seem to have worked by trial and error. Experience has been called the best teacher however bridge failures were not uncommon.

Wednesday, March 16, 2005

Wooden Trusses of a Covered Bridge.

Hannaway Covered Bridge Posted by Hello

Covered bridges use wooden trusses not unlike those in metal truss bridges. The triangular wood trusswork is clearly visible in the interior of this wooden covered bridge. This type of bridge gave way to iron truss bridges in the late 19th century. The bridge cover or roof is there to protect the wood from rapid deterioration due to rot. Iron doesn't rot or burn!

The Hannaway Covered Bridge is located in Fairfield County, Ohio. It is closed to traffic being bypassed by a modern bridge.

What's a Metal Truss Bridge?

Westerville Truss Posted by Hello

A turn of the century (19th) steel truss bridge. A metal truss is generally a triangular framework designed to have greater strength than a simple beam of similar weight. There are many truss designs. The one in the photo is a Pratt double intersect through truss or Whipple truss. The narrow components are under tension, that is, being stretched. The thicker components are generally being compressed by the load forces.

This bridge is located in Westerville Ohio on a bikeway. It was recently moved from its original location and rehabilitated . It is the last metal truss bridge in the county. A number of these old bridges are receiving a second life on bike or pedestrian paths.

Tuesday, March 15, 2005

Initial entry!

Well here goes!

I hope to use this Blog as a supplement to my website http://oldohiobridges.com as a medium to discuss my hobby. I am interested in documenting the remaining old (that's pre 1920 for me) truss metal bridges in Ohio. There is no reason to limit any discussions to Ohio except that is the locale covered in my website.