Sewickley Bridge, Allegheny County, PA
The current Sewickley Bridge (1981) is a continuous Warren truss in the form of the cantilever structure it replaced. It is constructed of welded closed box girders. It includes bolted gusset plates at the junction of the members and the entire superstucture is painted "PennDOT" green. It crosses the Ohio River at mile 11.7 in the Dashields Dam pool. This structure is on the Ambridge USGS 7.5" topo quad map.
The crossbracing overhead is a combination of welded box girders arranged in a triangular configuration and haunched W-shape beams for the horizontal members. There are some box girders which have a single oval perforation toward their top. At each channel pier, there is an access door to the navigation lights below. There is lettering stencilled on the nearby vertical member showing the location.
The simplification of truss members (specifically in their fabrication) is evident. See the Elizabeth Bridge fieldnotes for more info on how the fabrication method and complexity aids in establishing a construction date. This is especially helpful when there is no builder plate, as is usually the case on newer structures.
A pedestrian sidewalk runs the length of the structure on the upstream side. The simple railing is composed of vertical aluminum tubing with a larger diameter top rail and is similar to that currently used on the Smithfield Street Bridge in Pittsburgh. The sidewalk may also be reached from steps at the north approach which ascend from Chadwick St.
A plaque mounted on one of the vertical members near the southern channel pier may be viewed from the The plaque reads:
Richardson, Gordon & Associates, Inc.
Awarded in 1982 by
American Institute of Steel Construction Inc.
(includes the AISC and Steel logos)
The Sixth Street Bridge in Pittsburgh won this AISC award in 1928.
The bridge (S.R. 4025) connects PA51 [Narrows Run Rd to the west / Justice Michael A. Musmanno Memorial Boulevard to the east] at its south end with Ohio River Blvd [PA65] on the north. Kramer St intersects the northern approach from the east. Broad St is aligned with the bridge deck across Ohio River Blvd. The two-lane concrete deck carries the Orange Belt of Allegheny County's Belt Route System. Many road maps incorrectly show the Yellow Belt also crossing here, but that Belt crosses the Ohio River via the I-79 Neville Island Bridge and the 1995 Coraopolis-Neville Island Bridge.
The current bridge rests on the piers of the previous bridge. About 30 feet of concrete sits atop the rusticated stone piers which support the channel span. The previous bridge had a vertical clearance of 73.4 ft, so I will estimate the current bridge deck to be approximately 100 ft above the Ohio River's surface. The previous bridge horizontal clearance was listed at 724 ft., however when I paced the distance (admittedly inaccurate) I measured each anchor span of the cantilever at approximately 300 ft (10 modules) and the main span at about 585 ft (20 modules).
A set of code numbers stencilled on one of the downstream diagonals at the northern portal reads:
Assuming the survey measurements were 10 ft increments that may indicate the superstructure length to be 1133.5 ft. My paced estimate was 1169 ft. The other figure indicates a construction date of October 1981.
At the south end, there are two concrete bents: one supports the anchor span of the cantilever and a set of six continuous W-shape girder stringers. These girders have welded stiffeners where they pass over the second bent and continue to the concrete wingwall abutment. This abutment shows indications of having been built in multiple phases, so it may be that it may have been part of the earlier bridge. Two westbound lanes of PA51 bypass the bridge intersection by passing under one opening of this approach span. The other opening is used by the PLE Railroad (CSX) for a single track, although there used to be two tracks.
The hillside at the south end of the bridge has been cut away for PA51 revealing the sedimentary layering of rocks. This hillside is a fossil bed which includes a dense layer of seashells and crinoids. Unfortunately, the hillside is not very stable and is marked with No Trespassing sign erected by PennDOT.
Above the wingwall abutment, on the concrete curb to the eastern side of the intersection at PA51, there is a U.S. Coast and Geodetic Survey Benchmark which reads:
1960 (line overstriking this date)
At the north end, the approach span construction is similar except that there are three concrete bents in addition to the concrete abutment. Through the openings pass three tracks of Conrail (formerly Pennsylvania RR, and originally tracked as part of the Pittsburgh, Fort Wayne & Chicago [Ohio & Pennsylvania]) with as many as four tracks. Another opening was used as part of a driveway for the Pennsylvania Railroad station which sits adjacent to the north approach of the bridge. Chadwick St. passes under the third opening under the north approach.
This PRR station is the second Sewickley station and was built on this location when the tracks were moved from the present location of Ohio River Blvd closer to the river bank between 1926 and 1929. The 1885 station building was also moved in October 1929 to a location about 5 blocks west at 20 Chadwick St. It is now the Walter Robinson American Legion Post 450, and was never again used as a railroad facility.
About one block back toward the bridge is the intersection with Ferry St., presumably the location of the landing for Stoops Ferry which crossed the Ohio River to a point near the outlet of Narrows Run Rd. It was operated by William Stoops until the construction of the first Sewickley Bridge. Along the south bank of the Ohio, PA51 follows Stoops Ferry Rd at its intersection with Narrows Run Rd.
The railroad was built through this area around 1851. Sewickley Borough was incorporated in 1853. The town began to grow further after the initiation of interurban trolley service to Beaver.
The first Sewickley Bridge was also a cantilever structure, but used riveted girders and lattice. Two finials which decorated the top of the bridge survive. There were two capping each end of the bridge. One, colored white, is stored near the 1929 PRR station on Chadwick St. The other, colored copper green, is displayed in a park area on Ohio River Blvd at Walnut St. A five-foot-high bronze keystone builder plate rests on a white marble foundation next to the finial. The plaque reads:
Bridge No. 1
Fort Pitt Bridge Works
Pittsburg (sic), PA
Adam Laidlaw & Co.
The green finial rests on a platform with this inscription:
Sewickley Bridge Finial Dismantled 1980
Placed by Sewickley Valley Historical Society 1998
A Corp of Engineers drawing of the first bridge shows the design to be a cantilever with members arranged similar to a Baltimore Pratt truss. It is shown to have 23 vertical members in its channel span, plus the verticals at each channel pier, and an additional eight (plus one cripple) vertical members on each anchor span. The south approach is shown to have been a subdivided double Warren truss simple span crossing the PLE RR. Older maps show the north approach landing short of Broad St which would have been on the far side of the railroad tracks (present PA65). The approach ramp is shown to turn to the east onto Kramer St. A footbridge crossed the railroad at the intersection of Broad St and Bank St and Chestnut St was the grade crossing near the first train station.
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