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Historic American Engineering Record
Monongahela Connecting Railroad Company
Hot Metal Bridge
HAER No. PA-277-C

Crossing the Monongahela River at mile post 3.1
Allegheny County


National Park Service
Northeast Region
U.S. Custom House
200 Chestnut Street
Philadelphia, PA 19106


HAER No. PA-277-C

Location: Crossing the Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, Pennsylvania

USGS, Pittsburgh East Quadrangle, Universal Transverse Mercator Coordinates 17.588150.4475609

Date of Construction: Circa 1900

Engineer: Structural Department of J & L Limited

Architect: Unknown

Present Owner: Monongahela Connecting Railroad Company

Present Use: Out of service since May 1979

Significance: Fommerly enabled the hauling of molten iron from J & L Blast Furnaces on the north side over the bridge to the Open Hearth Furnaces on the south side of the Monongahela River

Project Information: LTV Steel Corporation has demolished its steel-producing facilities in its South Side plant. As a result, the Mon Con has applied to the Interstate Commerce Commission for and received permission to abandon its rail lines and facilities on the South Side. The bridge will be sold to LTV for use as a utility bridge. It currently carries, along with the Main Bridge, approximately 20 utility lines of various types.

Richard L. McCombs
Vice President - Operations
Monongahela Connecting Railroad Company
3600 Second Avenue
Pittsburgh, Pennsylvania

HAER No. PA-277-C
(Page 2)

The Hot Metal Bridge crosses the Monongahela River at Mile Post 3.1 in the City of Pittsburgh, Pennsylvania. It formerly provided access to the South Side Open Hearth Furnaces of LTV Steel (formerly Jones & Laughlin Steel Corporation) for hot metal (iron) produced in the North Side Blast Furnaces. The bridge has not been used for rail traffic since May, 1979 when LTV Steel replaced its open hearth furnaces with electric arc furnaces, idling both the blast furnaces and open hearth furnaces. The blast furnaces were demolished in the mid 1980's. Demolition of the electric arc furnaces was completed in June, 1993 along with the south end connection to the Hot Metal Bridge.

The Hot Metal Bridge is built on piers common to the Main Bridge and immediately down river from it. The span lengths and description follows:

Span NumberLengthType
Skew129'-2"Pratt-through truss
1154'-0"Pratt-through truss
2132'-0"Pratt-through truss
3321'-4"Pratt-through truss
4195'-9"Pratt-through truss
5135'-0"Pratt-deck truss
6102'-0"Pratt-deck truss

The spans are numbered from North to South and are on an ascending grade of 1.5% in the same direction. Truss members are pin connected. Expansion was originally provided by roller nests, however, these rollers were replaced with bronze slide plates in the early 1950's.

The Mon Con was chartered in 1885 as a subsidiary of Jones & Laughlin Steel Corporation. The original bridge between the north and south side plants was built in 1887. It is presumed that originally the molten iron was transported across this bridge. The present Hot Metal Bridge was begun in 1899, per Board of Director minutes of June 5, 1899 authorizing company engineer E. K. Morse to proceed with plans to widen the existing piers. The bridge itself was designed by the Structural Department of Jones & Laughlin Limited; fabrication and erection by Edgemore Bridge Works of Edge Moor, Delaware. This information is from the original drawings which are dated in the later part of 1899. Board of Director minutes of February 12, 1901 note that the Hot Metal Bridge was completed at a cost of $441,882. Steel used in the bridge was "soft open hearth steel" or "Bessemer Steel" per the drawings. The Hot Metal Bridge, as it currently stands, is essentially the same structure that was originally constructed, except for some modification that are listed below.

HAER No. PA-277-C
(Page 3)

There have been a number of repair jobs done to the bridge during its lifetime. The most significant projects are as follows:

a. Bridge inspections performed in 1950 indicated that the original roller nests which provided for expansion were frozen. An engineering/contracting firm -- Carl J. Jacobsen Engineers and Contractors, designed and installed bronze slide plates that year.

b. Jones & Laughlin Steel Corporation began a program in 1960 to improve steel production. One of the areas was to replace the fleet of 80 ton submarine ladles with 165 ton ladles. This required considerable work on the Hot Metal Bridge in order for the Mon Con to handle the heavier and longer submarine ladles. The first phase was to reduce the dead load. This was accomplished by removing the heavy fire brick trough that made up the deck system and replacing it with a light steel plate covered with granulated slag. This was necessary to prevent any hot metal splashing into the river. This work was done under traffic by company forces. The second phrase was to strengthen the top chord truss members. This was done by drilling holes in the web of the truss members and bolting with high tensile bolts through reinforcing plates. Over 7,000 bolts were placed. The work was designed by Structural Associates of Pittshurgh and erected by company forces.

The bridge has not been used for rail traffic since 1979. LTV Steel uses a portion of the bridge to support utility lines. The bridge will be sold to LTV for use as a utility bridge.

Index to Photographs

Page created:
Last modified: 08-May-2002

HAER Text: Richard L. McCombs, Vice President - Operations, Monongahela Connecting Railroad Company
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