Morgan Ford Bridge

Crossing of the Smith River in Henry County, VA

While the National Bridge Inventory lists this bridge as having been built in 1953, it is apparent from looking at it that this information is only partially correct. In all likelihood the bridge's piers and plate girder approach spans date from this period, as well as the concrete deck and riveted steel guardrails. However, the main span of the bridge is of a design that was not contemporary in the 1950s: the pin-connected Pratt truss. Instead, this span was more than likely a recycled one, relocated from a busy crossing to this sparsely-populated corner of Southside Virginia. The pony truss span located on the east shore is of a slightly more modern design, with a Warren configuration and riveted connections; it is obviously of a different vintage than the main span. This mismatch of bridge designs clearly points to a reuse job, done at a time when massive highway expansion was underway and funds were scarce, when transportation officials realized that a lightly-traveled crossing didn't necessarily have to be strong enough to carry an entire armored division. The legacy of this decision remains today, as the bridge continues to meet traffic needs while enhancing the beauty of this scenic river.

I can only speculate on the original date of construction for either the main span or the pony truss span. Since the bridge features two lanes of a decent width (11-feet is below the modern standard, but generally not "mirror-busting"), it was probably constructed for an automobile road, something that did not occur on a large scale until the 1920s. Wide bridges were built in urban areas, but then these most often have sidewalks (but not always, of course). The span also features a slight amount of design embellishment, in the form of the rounded "arms" that hold up the portal bracing. As truss bridges became more standardized in the 1930s and 40s these little touches gave way to square utility. Thus, my guess would be that the bridge was built in the 1920s or perhaps early 30s. Without an original plaque, however, I can't be certain that this is the case.

The design of the main span is a standard Pratt with eight panels, one of the more common configurations. Its vertical structural members consist of built-up beams, held together with V-lacing (the zigzagging metal on the outside). On four of the beams, the V-lacing has been partially replaced by steel plates with oval-shaped holes, a more recent design, possibly added in the 50s to strengthen these members. The diagonal members, as well as those on the bottom chord, are made up of eyebars (long steel bars with holes at each end). The bracing that connects the two trusses together at the top is comprised of lattice, as well as the aforementioned little curved arms that hold up the bracing; these two features make the bridge nice to look at as you drive through it.

The pony truss is a more simplistic design than the main span, though certainly far more interesting than a modern bridge. All connections are made with riveted gusset plates, with none of the rivets having been replaced with bolts. There is a possible cut in the middle of the top chord, which may be a sign of the span having been moved from another location. Except for the two middle diagonals, all of the span's structural members are I-beams. The middle diagonals are built-up latticed beams, made stronger because of their importance (the diagonal members are more important than the verticals in the Warren configuration). Unfortunately, due to the steep bank, I couldn't get underneath the pony truss span to photograph the underside, but I assume the floor beam configuration is similar to that of the main span.

The bridge features three approach spans, all of the plate girder design. Plate girders function in a similar manner as trusses: the structural load is borne by two large parallel beams, instead of trusses; these two beams are the only parts of the bridge that touch the piers. The floor beams that hold up the road deck connect to the girders perpendicularly; they also function as the bracing that holds the two girders together. Bad lighting prevented me from photographing the undersides of these spans, but a good picture of a more substantial plate girder span can be found on the US 701 Cape Fear River Bridge page. In the truss bridges I have encountered, however, this design is usually not employed on relatively short spans such as these; the steel stringer design is predominant. Perhaps this decision was made to hold down costs, or it made sense for the length of the spans. The span on the west shore is the longest, connecting the main span to the abutment. Its girders protrude halfway above the roadway, while the girders of the two east shore spans are visible only from the outside of the bridge.

With a low traffic count and a 44% sufficiency rating (not dire considering the bridge's location), this bridge is most likely not in the cross-hairs of Virginia's transportation department. Ample signage directs overweight and oversized vehicles away from this section of road. However, DOTs are always eager to undertake wasteful projects if not for psychological reasons alone, such as the public's confidence in a bridge with surface rust. And then Virginia will be one step closer to becoming like its neighbor to the south: a near-desert for historic bridges.

Located upstream of this bridge is a series of tall stone piers from a previous bridge, or a few successive bridges most likely. Interesting enough the road alignment of the old bridge was short and straighter than that of the current bridge. The current bridge, notably, is located beyond a blind downhill curve on the western bank. The spans of the previous bridge were about half the length of the current bridge, since there are piers on both banks as well as one in the middle of the river. In all likelihood this bridge was too narrow and too lightweight for the increased weight of post-WWII automobiles.

Facts

Year erected: 1953
Route Carried: SR-622 (Morgan Ford Road)
Crosses: Smith River
Location: Henry County, VA
Design: Eight-panel, pin-connected Pratt through truss (main span); Six-panel, rivet-connected Warren pony truss (east shore span); Plate girder approach spans.
Number of spans: 5
Main span length: 137.1 ft. Total length: 396 ft.
Inside width: 22 ft., two lanes
National Bridge Inventory ID: 10112
Coordinates: 36°33'32.00"N, 79°44'45.36"W

Pictures

Left: a view of the main span, from the south. Center: the two center truss panels. Right: two outer panels, showing a later modification to a vertical member.

Left: a portal shot, facing east. Center: inside the truss web. Right: the underside of the main span.

Left: a top chord / front post connection. Center: a top chord / vertical connection. Right: a bottom chord connection.

Left: a pinned connection, viewed from below. Center: the curved part of the portal bracing. Right: the location of the bridge plaque.

Left: an oblique shot of the Warren pony truss span. Right: a shot of the two outer panels.

Left: a front post / top chord connection. Center: a top chord connection. Right: a different angle of the same connection.

Left: a portal shot of the entire span. Center: the east bank approach spans. Right: the bridge railing, also showing a part of the western approach span girder.

Left & Right: various shots of the previous bridge's central pier.

Morgan Ford Bridge