The behaviour of skewed masonry arch bridges

Masonry arch bridges have been used throughout the world. Many thousands exist in Europe.The number of arch bridges in the United Kingdom has been estimated at 75,000 withapproximately equal numbers occurring within the road and railway networks.The arch is very pleasing to the eye. Many arch bridges are listed structures so thatreplacement schemes are not options. In 1880 Baker was commissioned to report on thedeterioration of Telford's Bridge at Over. Baker wrote, "The abutments had gradually goneover, and had been continuing to go over for sixty years. The result was that certain barbarianswere actually urging the magistrates to take down the bridge...". He continued, "... cracks inthe spandrels were big enough to walk through quite comfortably. It would be a disgrace to thecountry if they pulled down Telford's historical work and substituted a hideous iron latticebridge",(Heyman & Threlfall, 1973).Masonry arch bridges were built to carry a road, a railway or sometimes a waterway over anobstacle. A right arch bridge was used where the crossing could be perpendicular to theobstacle. In contrast, a skewed arch was built wherever the obstacle and over-road intersectedat any angle other than 90°. Thus, a right arch is a special case of the more general class ofskewed arch. The extent of existing knowledge of the behaviour of arch bridges is limited tothe right arch in which many effects have either been omitted or have been simplified. Theseeffects include the spandrel walls, the backfill, irregular geometry, and eccentric loading.Clearly, there is scope for an advancement of knowledge so that these effects may be consideredand ultimately the behaviour of the skewed arch bridge can be described.The construction of arch bridges in Great Britain reached its zenith at around the beginning ofthe Nineteenth century. At this time, if conditions prevailed, there was a general desire for eachnew bridge to exceed the span of any that had gone before (Ruddock, 1979). However,Sejourne (1913) could only find eight structures in the United Kingdom that had at least onespan with a clear opening of more than 40.0 m