Three Span Bridge

Bridge Dimensions

In advance of performing an intrusive investigation, a variety of scenarios were explored, including a case where masonry backing material was present above the piers (commonly encountered in multi-span bridges).

In this case the critical failure mechanism involved two spans. This clearly demonstrates that it is potentially unsafe to analyse the bridges as a series of single spans simply because the piers are deemed to be 'stocky' (as advocated in some assessment codes).

Three span masonry arch bridge being surveyed	Analysis of bridge using LimitState:RING

Single Span Bridge

Bridge with multiple arch rings

Very short span bridges will often be most vulnerable to the damaging effects of excessive live loads, because their self weight is relatively low in relation to that of an axle load. This very short span UK highway bridge comprises an arch with several courses of brickwork rings.

In advance of performing an intrusive investigation, various scenarios were considered in LimitState:RING, including:

• Assuming the rings were debonded (acted separately) and,
• Assuming the mortar is sufficiently strong to ensure ring separation does not occur (in a very short span structure, inter-ring stresses will be low).

Analysis of bridge using LimitState:RING a) assuming debonded rings and b) assuming bonded rings

Both the above mechanisms involve sliding failure (either circumferential or radial) rather than a traditional '4-hinge' failure, something which would not identified using most other arch analysis software programs.