View source for NC 87 & 100 Railroad Overpass

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You can spot it from at least a 1/4 mile down the road, that towering of hulk of steel, rust red and faded black. It seems almost too tall and too imposing for a mere overpass crossing a two-lane road; such a structure belongs over a river or a canal. But there it hovers over the roadway, a reminder that you have just entered Burlington, North Carolina, a city built because of the railroad.

This bridge could also be described as the "survivor bridge." It is the last of its kind in Alamance County, a place that once had many truss bridges traversing its creeks and river, a place that exists as the NCDOT's blueprint for the entire state: one homogeneous concrete slab after another. And neither is this bridge immune to this destruction. It is owned by the same owner as those eradicated structures, the State of North Carolina, under its subsidary, the North Carolina Railroad Company. Supposedly it is insufficient for "double-stack loads." Of course this is probably a legimate issue, though it may be merely an excuse for "standardizing" the line. There are other things going against it as well, notably its low clearance underneath. But it will be a shame to lose yet another interesting bridge to a forgettable modern one.

The road that travels underneath the bridge carries NC routes 87 and 100. 87 is the longest NC route, while 100 is the original routing of NC 10, the Central Highway, which became US 70 (NCRoads Annex). By 1938, when this bridge was built, the state's most important highway (up until the building of the interstates) no longer passed through on this route.

One of the more interesting features of this bridge is how it meets the roadway at an angle. The roadway on both sides comes within five feet or so of the opposing corners of the abutments. Yet, if the bridge met the roadway at a right angle it could support 8 or more lanes underneath. In other words, the bridge crosses over quite a bit of dirt.

The design of the bridge, the Warren truss, is one that seemed to take off in popularity around this time. From the perspective of the novice it appears to be a simpler design, relying on fewer but heavier components. The bridge, in particular, appears to have been built very strongly. In the above picture note how massive the steal beams closest to the camera, called the front posts, seem in comparison to the rails. The riveted gusset plate connections are equally impressive, larger anything I've seen in the state. Clearly, the engineers of this structure designed it to carry significant loads year after year, decade after decade, and into the next century. This is not to say, however, that the strength is derived from brawn alone. There are some design features that allow it to span the distance without adding material, notably the slight arch shape to the bridge's top chord.

A really attractive feature to this bridge (I know this is subjective) is the "zigzaging" pattern of the bracing, the beams at the top and inside the truss that in a sense hold the sides together. The name for this is v-lacing and it is one of the examples of geometric complexity that will be lacking on its replacement.

=== Facts ===

* Year built: 1938
* Builder: Carolina Steel and Iron Co. of Greensboro, NC
* Route Carried: North Carolina Railroad
* Crosses: NC 87 and 100
* Location: Burlington, Alamance County, NC
* Design: Polygonal Warren truss
* Total length: 166 ft.
* National Bridge Inventory ID: 10108
* Coordinates: 36° 6'44.58"N, 79°28'15.17"W

=== Photos ===

[[File:nc87_100_rr1.jpg|200px]][[File:nc87_100_rr2.jpg|200px]][[File:nc87_100_rr3.jpg|112px]]

* Left: Oblique view, facing west. Center: Oblique view, facing east towards Burlington. Right: Portal shot, facing south.

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* Left: Underside of the bridge; Center: Oblique view of the bridge's inside. Right: the large gusset plate connection between the front post and bottom chord, along with a bearing.

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* Left: a lower chord connection. Center: a front post / top chord connection. Right: the cracked plaque.