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| Key Facts |
| Bridge Name | Facility Carried / Feature Intersected | Location | Structure Type | Construction Date and Builder/Engineer | |
|---|---|---|---|---|---|
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Smithfield Street Bridge
| Smithfield Street Over Monongahela River | Pittsburgh: Allegheny County, Pennsylvania | Metal 13 Panel Pin-Connected Lenticular Through Truss, Fixed and Approach Spans: Metal Rivet-Connected Polygonal Warren Pony Truss, Fixed | 1883 By Builder/Contractor: Andrew Kloman and Engineer/Design: Gustav Lindenthal |
| Technical Facts |
| Rehabilitation Date | Main Span Length | Structure Length | Roadway Width | Main Spans | Approach Spans | NBI Number |
| 1994 | 360 Feet (109.7 Meters) | 1177 Feet (358.7 Meters) | 42 Feet (12.8 Meters) | 1 | 6 | 23027002000000 |
This
is arguably Pittsburgh's most important historic bridge. It has five
commemorative plaques on it, including one listing it as a National Historic
Landmark, which is the highest and rarest honor the United States can bestow
upon a bridge!
This bridge appears to be the only surviving example of a lenticular truss that is not associated with The Berlin Iron Bridge Company or its predecessor the Corrugated Metal Company, which held patents on a lenticular truss design. The Historic American Engineering Record instead points to a much earlier patent by Edwin Stanley which shows a similar truss configuration, as the inspiration for the design of the Smithfield Street Bridge. With its two 360 foot spans, the Smithfield Street Bridge displays the longest lenticular truss spans known to remain in the United States. Compare this to the otherwise large 198 foot span of the Bardwells Ferry Bridge. The Smithfield Street Bridge is also noted for being one of the first bridges in the United States to use steel in its trusses as opposed to exclusively wrought and cast iron.
The bridge was originally built in 1881-1883 as two truss lines wide, but in 1889-1890 a third truss line was added to widen the bridge. In 1911, it was widened by a much smaller amount, and one of the trusses was simply moved over. Shortly after this time as part of the project, the original cast iron portals were replaced with the ones seen today in 1915. A some later date, the approach spans were reconfigured, and today a riveted pony truss span is part of the southern approach.
As
one might imagine, for a bridge that was altered so much in its early life, and
further has remained functioning in a major city in the 21st Century, the
Smithfield Street Bridge has been significantly altered from its original
design. The earlier alterations can be dismissed since they are so old and were
done early enough in the history of the bridge that these alterations are
themselves historic. However, there are numerous modern alterations including
rivets replaced with bolts, welded steel added to various parts of the bridge,
concrete fill added to the center end posts, and
missing original railings.
These alterations have diminished the historic integrity of the bridge, however
the bridge retains enough of integrity of materials and design to maintain an
extremely high level of historic and technological significance. In addition,
historical photos of the bridge show the original
sidewalk railings on the bridge which were extremely ornate, far more beautiful
than the utilitarian railings present today. There are some railings along some of the streets near
to the southern approach of the Smithfield Street Bridge that look suspiciously
like the railings seen on the bridge in 1883. This railing is shown to the left.
These railings are similar, albeit different to the original railings. It would
be nice to see Pittsburgh replace the current railings with replicas of the
original railing. Chicago is another city that has in recent years replaced
non-original railings on its bridges with replicas of the ornate originals.
There is no reason why Pittsburgh could not do the same.
The
bridge's bottom chord eyebars have, like much of the bridge, been significantly
altered over the bridge's long and colorful history. Unfortunately a decision to
weld plate onto the surface of the eyebars had the highly unfortunate effect of
covering up an important piece of history on the bridge. Only some of the
eyebars escaped alteration. On those, a label is visible. Shown in the picture
to the left, it reads Kloman Patent Process 1881. Andrew Kloman was the owner of
a local mill in the Homestead area that produced a variety of iron and steel.
Kloman held several patents, one of which related specifically to the
fabrication of up-set eyebars, which is the patent that the marks on the Smithfield Street
Bridge's eyebars refer to. Kloman and his mills would later become associated with the
famous Carnegie Steel Company. Because these labels on the eyebars are important
for interpreting the history of the Smithfield Street Bridge, any future repairs
to the bridge should take into account the significance of these labels, and
should not hide or cover up these surviving markings.
Some claims have been made or may have been made about the Smithfield Street Bridge which are not true or are disputed. The bridge is not the oldest metal truss in the country, since the Reading Hall Station Bridge is decades older, nor even the oldest steel truss in the country, since the 1879 Glasgow Railroad Bridge is older. The bridge is sometimes called a "Pauli" truss, the definition of which is not agreed upon according to this article (PDF version).
Above: These photos show the bridge after it was widened but before the new portal bracing was installed. Source: Library of Congress
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Structure Overview
Original / Full Size Photos |
A collection of overview photos that show the bridge as a whole and general areas of the bridge. For the best visual immersion and full detail, or for use as a desktop background, this gallery presents the photos for this bridge in the original digital camera resolution. |
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Structure Details
Original / Full Size Photos |
A collection of detail photos that document the parts, construction, and condition of the bridge. For the best visual immersion and full detail, or for use as a desktop background, this gallery presents the photos for this bridge in the original digital camera resolution. |
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Structure Overview
Mobile Optimized Gallery |
A collection of overview photos that show the bridge as a whole and general areas of the bridge. View the photos for this bridge in a reduced size which is useful for mobile/smartphone users, modem
(dial-up) users, or those who do not wish to wait for the longer
download times of the full-size photos. Alternatively, view this photo gallery using a popup slideshow viewer (great for mobile users) by clicking the link below.
Browse Gallery With Popup Viewer |
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|
Structure Details
Mobile Optimized Gallery |
A collection of detail photos that document the parts, construction, and condition of the bridge. View the photos for this bridge in a reduced size which is useful for mobile/smartphone users, modem
(dial-up) users, or those who do not wish to wait for the longer
download times of the full-size photos. Alternatively, view this photo gallery using a popup slideshow viewer (great for mobile users) by clicking the link below.
Browse Gallery With Popup Viewer |
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