St. Vincent High Bridge

The Pennsylvania Railroad erected the original St. Vincent High Bridge in 1890 to carry Monastery Road over its main line, just north of St. Vincent College in Unity Township, Westmoreland County. The Double Intersection Warren Truss Bridge featured a main span of 150’-0” and an overall length, with two approach spans, of 228’-0”. Gibson-Thomas Engineering was retained by the Unity Township Supervisors to replace the existing narrow, one-lane bridge which had limited sight distance due to the crest vertical curve. After consideration of several alternatives and a desire to maintain railroad clearances and avoid conflicts with several fiber-optic lines in the vicinity of the project a three span replacement with an overall length of 230’-0” was selected. All spans consisted of spread prestressed box beams with a composite reinforced concrete deck. The final bridge and roadway template was determined in accordance with current PennDOT criteria and comprised two 12’-0” lanes and two oversized 8’-0” shoulders. The oversized shoulders were included to act as pedestrians/cycle lanes for connection to St. Vincent College, Winnie Palmer Nature Reserve Trails and Legion Keener Park in Latrobe. The width being increased from 16’-0” to 40’-0” greatly increased safety for the nearly 5,000 vehicles per day which utilize the structure. It is also important to note that the structure was lowered nearly 20’-0” to eliminate the vertical curve and that no interference with the railroad occurred due to the fact that the original structure was over 100’-0” above the tracks.

This major project which was constructed over two seasons due to the nearly 60 trains per day utilizing the tracks was completed on schedule and under budget. The savings were due to collaboration with the Department and the contractor to institute a unique shoring system for removal of the existing main span which did not interfere with rail traffic and allowed the truss to be dismantled without anything falling onto the tracks below.


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Gibson-Thomas Engineering Co., Inc. is a multi-discipline consulting engineering firm established in 1916 in Latrobe, Pennsylvania. Our past experience, key staff and commitment to total client satisfaction are the major factors that our clients consider when contracting with Gibson-Thomas Engineering.

724-539-8562
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