US 701 Cape Fear River Bridge

Known by the state as Bladen County Bridge No. 17

Bridge Number 17 is not the sort bridge that would be displayed proudly on the county's website. It has probably never been painted by an artist, and few have likely felt compelled to photograph it. However, while not beautiful nor particularly unique, this bridge isn't without its merits. A deck plate girder bridge, it functions in a similar manner as a deck truss bridge in that the outside parts of the structure, the girders, bear the load of the deck, with the floor beams strung off of them. There are connections, some of them riveted, holding the two girders together via bracing, similar to how the bottom and top of a truss bridge is held together. A bridge using this design would not be built today, due to its "non-redundant" design. If one the girders were to fail it would set off a chain reaction that would probably send all three center spans into the river.

The girders themselves function using the cantilever method. Notice how the girder is widest above the two inner piers. It is on these piers that one half of the main span is extended from, balanced out by the other span's connection to the outer pier. To visualize how this works, imagine stacking some concrete blocks underneath one end of a seesaw, high enough to be level with the pivot. You secure the seat to the blocks and then put another block on the opposite seat, the one that has nothing underneath it. It can't possibly tip back, because the other side is balancing it out. What you have in the seesaw is one half of the main unit of this bridge, with the block representing a car on part of the main span. In fact, if you were to cut away cleanly one half of the girder portion of the bridge the other half would probably still stand. With the modern flyover ramp next to it, which is a basic steel beam bridge, if you made the same cut, at the center of the main span, the entire main span would collapse, but the outer two spans would be unaffected. Of course, the bridge's design doesn't allow the two halves to be independent of one another. No matter where a girder failed on the main span, the weight from above would probably force both halves to drop.

The bridge, which carries US 701 Southbound and NC 41 Westbound over the Cape Fear River directly outside of Elizabethtown, was built in 1957. Unlike the NC 11 and Tar Heel Ferry Road bridges, this structure was built as apart of a widening project. The existing US 701 bridge at the time, located where the 1986 flyover ramp stands now, was a striking 1923 Pennsylvania truss bridge called McGirt's Bridge.

Photo taken by the Historic American Engineering Record (HAER NC-29)

McGirt's Bridge, the state's longest fixed truss span at the time (at 350 feet), was wiped from the face of the earth in the 1980s, when so many of NC's fine bridges were lost. In the above picture the railing of the 1957 bridge is visible. Notice also how at one time the state did modify the 1923 bridge, retrofitting it with 1950s style railings. From a practical perspective the bridge was probably narrow and unsafe. But then again we will never see a structure like it built again. Notice how the piers straddle the river. In contrast, both the 1957 and 1986 bridges have piers well out into the river. The 1923 structure was much more of a sophisticated design.

I refused to photograph the 1986 structure because of the scrapping of its predecessor. I couldn't avoid getting it in some of the pictures of the 1957 bridge though. If you need to visualize it, just take a trip down any interstate in the state, and imagine that you are on one of the most important rivers in the state, instead of driving under a highway overpass. The 1957 bridge doesn't deserve that description. It at least looks like a river crossing.

The underside of this bridge was home to a number of swallow nests, notably on the span between the river and the north shore, when I kayaked under it in April of 2009.

Facts

Year built: 1957
Route Carried: US 701 Southbound and NC 41 Westbound
Crosses: Cape Fear River
Location: Elizabethtown, Bladen County, NC
Design: Cantilever deck plate girder main span with prestressed concrete stringer approaches
Length of main span: 160 ft. Total length: 1176.9 ft.
Inside width: 27.9 ft., two lanes
Vertical Clearance Underneath: 52.8 ft.
Sufficiency Rating: 50.2 out of 100
National Bridge Inventory ID: 17016
Coordinates: 34°37'57.51"N, 78°36'10.95"W

Pictures

Left and right: the main span of the bridge, viewed from up close and afar.

Left: the balancing portion of the cantilever system and a bridge bearing. Right: a connection between the girder and underside bracing.

Left: the underside of the northern outer girder span, where there were a few swallow's nests. Right: the approach spans.

US 701 Cape Fear River Bridge