Passive pressure development in masonry arch bridges

Abstract

This paper considers the development of lateral passive pressures during the failure of masonry arch bridges. It has been known for some time that the sway failure mechanism of these bridges develops significant stabilising soil pressures but quantitative figures for use in bridge assessment remain largely unknown, particularly for deep arches. This paper considers the pressures developed for two geometries typical of the range of structures found in the UK, one of span/rise = 4 and the other semicircular. The experiments were performed in a geotechnical centrifuge using 1/12th scale models of a 6 m, single-span, three-ring, brickwork arch. The results confirm earlier work suggesting that full passive pressure limits are not reached; however, it is clear that for the soil type tested limiting soil pressures at all monitored locations were achieved. A passive pressure profile is postulated for arch bridge assessment and application of the profile to the assessment of the two bridges tested is undertaken.