Date of Award


Document Type

Master Thesis

Degree Name

Master of Engineering (Research)


Department of Civil, Structural and Environmental Engineering

First Advisor

John J. Murphy

Second Advisor

Kieran Ruane


Masonry arch bridges comprise a significant proportion of the bridge stock both nationally and internationally. They have proven to be enduring structures, far surpassing their design lives and with relatively low life-cycle costs, are environmentally friendly (Sustainable Bridges, 2007).

New masonry arch bridges are not generally constructed. However, their ageing materials paired with ever increasing traffic loads have led to the necessity for their periodic re-assessment. Masonry arch bridge design was predominantly by rule of thumb and their re-assessment has been subject to a number of simplified assumptions. One such simplification, the bridge “effective width” is studied in this thesis.

A literature review was undertaken and a preliminary study was carried out on a masonry arch, assessing six point load locations and three variations of skew. Arch displacements, axial stresses and axial force envelopes were determined.

This informed a more complex study, where parameters such as: arch stiffness, fill stiffness, fill depth, arch shape, arch span/rise, abutment stiffness, ring thickness and bridge skew were studied. This model was verified using displacement test data obtained for Griffith Bridge, Dublin, by Fanning and Boothby (2001) and strain data obtained for Pop Bottle Bridge, Lincolnshire, by Gifford Ltd (2002). The effective widths of a series of bridges with varying parameters were studied.

Statistical analysis was used to determine the most influential factors on the effective widths of masonry arch bridges. Once these were determined, a formula for the calculation of effective width was derived and compared with the effective width prescribed in BD21/01 (Department of Transport, 2001). Stress concentrations were identified on the arch, and stress concentration factors were established for a number of bridges.

The influence of skew on masonry arch bridges was also studied. Effective width envelopes were obtained, and the influence of abutment stiffness on the bridge displacements under a series of point loads was examined.

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