Masonry bridge rating technique developed
About 1,000 masonry arch road bridges and 2,000 rail bridges built in the 1800s and early 1900s still are in use today. They are either difficult to rate for capacity or are unrateable with currently available techniques. But a new rating technique developed by Thomas Boothby, an associate professor of architectural engineering at Pennsylvania State University, could change that. The process allows bridge owners and consultants to evaluate stone bridges in the span direction with sophistication, accuracy and speed that is comparable to methods used for steel and concrete bridge rating.
To use the new system, an engineer needs a desktop computer and a simple frame analysis program that produces a 2-D picture of the bridge as an assembly or beams and joints. An engineer assesses the geometry of the structure and produces a sketch of the bridge, reducing a one-foot-wide segment of the arch barrel to a simplified system of bars and joints. Next, the engineer assesses the materials from which the bridge is constructed, and applies dead loads and live loads as transmitted through the fill.
“The technique calculates the stresses in the bridge and compares them to the assessed capacity of the materials,” Boothby says. The approach has been field-tested and validated on a bridge in Adams County, Pa.
For more information about the rating system, contact Barbara Hale at (814) 238-0997; e-mail: [email protected].
