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Allegheny Commons Park Pedestrian Bridge Renovation - Pittsburgh, Pennsylvania

by Tyler hauser 3. April 2012 08:06

R.A. Smith National provided 3D laser scanning services for the design and relocation of an existing dilapidated pedestrian bridge over the Norfolk Southern Railroad within the Allegheny Commons Park in Pittsburgh. 3D laser scanning processes were utilized to capture highly accurate point cloud data representing the structural aspects of the bridge.

The use of laser scanning to collect the needed as-built data was imperative. Typical survey locations were not possible based on existing site conditions, including the inaccessibility of the deteriorated bridge and railroad tracks that were located 25 feet below grade.

Unique scanner locations were critical to collecting enough data to replicate the bridge and also meet the railroad's clearance requirements. An existing 60-foot historic monument was also scanned to identify height, detail and plumbness.

A fully unified and registered point cloud data set was used to create an accurate TIN model for surface requirements. 3D line work was also extracted from the unified data to create the structural items of the bridge. Finally, a clearance report was created to illustrate the clearances to the arcing bridge above each set of the four railroad track systems below the bridge.

The final deliverable was utilized by Pashek Associates to coordinate the design and new location for the pedestrian bridge.

3D Laser Scanning the Wisconsin Rapids Bridge

by Tyler hauser 28. February 2012 08:20

Historic and offering simple elegance within a beautiful setting, a bridge with its design history lost is finding renewal through 3D laser scanning.

Privately owned, the historic bridge spans time as well as a portion of the Wisconsin River. The bridge services as the only access onto Belle Island in Wisconsin Rapids, Wis. The existing structure was made up of two, 75-foot spans, and included decorative railing and lighting. No record drawings of the existing bridge could be found.

R.A. Smith National laser scanned the entire bridge, including the abutment walls on both ends, and created a full-color, registered point cloud deliverable that was used by Olson & Nesvold Engineers in the replacement bridge design process. This enabled the design team to very accurately obtain vital dimensional information on the existing structure, as certain structural components and the overall aesthetics of the original bridge needed to be incorporated in the replacement design.

Additional challenges included steep, heavily vegetated slopes which made obtaining sufficient setup locations very difficult.

A topographical survey was also performed for a 75-foot area around each end of the bridge.

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