Analysis of Masonry Arch Bridges

By Ece Erdogmus

Abstract

Most of the Class 1 railroads across the United States and in Pennsylvania have been adopting a 315,000-pound maximum car weight rather than the previous 263,000 or 286,000-pound maximum car weight limits. However this upgrade creates a particular problem for shortline railroads, which do not have the capital or personnel to evaluate and upgrade their infrastructure. For this purpose, a study called "Heavy Axle Study" has been conducted for PennDOT, for documenting the rating and implication of the change in car weight limits on the short line railroad infrastructure (Laman, Gittings, Boothby, Leighty, Erdogmus, 2001).
Among the 1557 bridges reported to the project, 213 are concrete and masonry arch bridges. These masonry and concrete arch bridges, for the most part built in the late nineteenth century and early twentieth century, are often considered as "simple in design, complex in behavior" and their ratings are usually established based on engineering judgment by the owners of them. There are also other methods used in the literature, which analyze the load effects on masonry arch bridges only in span direction. However, using a recently developed three-dimensional nonlinear finite element model, it is possible to assess the filled arch bridges considering vulnerabilities in all directions, especially critical transverse effects, such as pushing out or overturning of the spandrel walls or development of longitudinal cracks. This study not only presents the rating of the arch bridges according to the new weight limits but also shows that the recently developed finite element analysis method is a powerful tool for analyzing railroad filled arch bridges, taking into account the material properties and interaction between the soil fill and concrete/masonry.