McMahon & Mann Consulting Engineering and Geology, P.C.

Mike Mann, P.E. Presents at the 25th Annual Statewide Conference on Local Bridges

October 23rd, 2019 8:24am
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Mike presented at the 25th Annual Statewide Conference on Local Bridges held in Syracuse, New York. The presentation titled “Remediation of Stone Arch Bridge” was authored and presented by Mike, Alexey Brumagin, P.E. of Chautauqua County, and Brian Carlson, P.E. of Greenman-Pedersen, Inc. 
Presentation Abstract:
The Chautauqua County Department of Public Facilities owns and maintains a two span stone masonry arch bridge in Jamestown, New York. The bridge is located on South Main Street and spans the Chadakoin River. The South Main Street Bridge is a historic arch bridge that was built circa 1872. The bridge is comprised of two stone arches with two abutments, a center pier, and stone spandrel walls and parapets. Plans for the original construction are not available although it was described in period newspaper articles.
A 2014 inspection of the bridge detected deterioration of the stone arches supporting the bridge. Large stones had fallen out of the arches and could be seen in the river bed. The resulting holes were several feet in size and allowed the soil and rock fill above the arch to drop out, exposing utility lines and the bottom surface of the sidewalk. The inspections also noted settlement of the upstream and downstream ends of the abutments and the pier. The worst area of settlement noted in the inspections was at the upstream end of the pier where 12 to 14 feet of the pier settled approximately 4 inches vertically. 
Based on the historic nature of the bridge, it was decided to rehabilitate the bridge instead of replacing it. The work included stabilizing the center pier foundation with micropiles and a reinforced concrete skirt to support the original stone pier. Work on the superstructure included removing the arch fill, constructing a reinforced concrete saddle over the stone arches, replacement and repair of the arch stone work and repair of the spandrel walls. 
During construction, the foundation for the center pier was exposed, providing an interesting snapshot into construction techniques in the late 1800’s. The presentation provided a description of the project focusing on the foundation improvement work done at the pier including, micropile design and construction, design and construction of the reinforced concrete skirt around the pier, and grouting of the center pier and foundation. 
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