Arch Bridge

This project involved the construction of a 50′-0″ clear span steel multi-girder structure with a composite, reinforced deck. The existing structure, built in 1914, was a single lane, concrete arch bridge with concrete spandrel walls retaining the dirt roadway fill. The bridge was determined to be an historic structure and recordation was performed for the Pennsylvania Historical & Museum Commission, before final design was completed. The width of the hydraulic opening was inadequate to ensure that flooding would not occur, since floodplain on either side of the channel is not present. Due to the location of the roadway, moving the bridge was not possible, and increasing the span as needed (80’ was determined necessary) made each approach a 90’ turn. Close cooperation with the Army Corps of Engineers was necessary to obtain dispensation for an interim solution, since the site is in the backwater area of the Conemaugh River Lake Dam. The structure span was increased from 39’-0” to 50’-0” and the far approach was depressed to create a channel for floodwaters without overtopping or increasing backwater. The depression of the far approach and location made an advisory speed limit necessary, as well as an extreme super elevation of the roadway and bridge.


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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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