J.A. KNUDTSEN(1), P. KABELE(2) and D.T. BIGGS(3)

(1) Czech Technical University in Prague, currently KPFF Consulting Engineers, Portland OR USA jonathan.knudtsen@kpff.com 

(2) Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic mailto:petr.kabele@fsv.cvut.cz

(3) Biggs Consulting Engineering, Saratoga Springs NY USA biggsconsulting@att.net

ABSTRACT

Masonry arch bridges are used in highway and rail systems throughout the world. Many of these are more than a century old, and experience much higher live loads than originally designed. Due to age and new live load criteria, it is often necessary to evaluate the existing load capacity. Despite masonry’s wide use, it is only recently that scientific approaches to design and analysis have been developed, but there is a lack of consensus on the conservativeness, simplifications used, and modelling rigor required. The primary purpose of this study is to compare various analysis methods, evaluating the results from the point of view of structural response, modelling efficiency, and variations in the inputs and assumptions used. The techniques considered include limit analysis using hand calculations, rigid-block analysis, finite element analysis using a smeared crack model, and finite element analysis using a discrete crack model. To demonstrate the methods, a 19th-century two-span stone masonry arch in Troy, NY, USA is used as a case study. The bridge underwent a significant intervention in 1986 in which the infill and spandrel walls were removed and replaced. At the time, the bridge was rated by idealizing the bridge as a series of elastic beams. The compressive stress and percent contact area were limited to allowable design values. A secondary purpose of this research was to compare the results of the elastic analysis with the results of the modern analyses, and to provide an updated load rating.

KEYWORDS: masonry, arch, bridge, finite element, rigid block, analysis