Experimental investigation of the residual behaviour of damaged masonry arch structures

New masonry arch bridges are rarely constructed as part of modern transport networks, however they continue to remain an integral part of modern civil infrastructure due to their overall resilience. This resilience has led to extremely long service lives which in turn has led to the majority of those bridges still in service being either distorted or damaged. Interest in the bridge owners community is directed towards prolonging the service life of these structures rather than replacement with new bridges. The aim of this paper is to explore whether the residual strength and the service life can be reliably established, and whether load limits must be imposed based on condition-based assessment, and/or retrofit the masonry arch system to prolong the life span of these important structures.

To investigate residual strength and safe working loads, large scale, soil-backfilled masonry arches were constructed and subsequently subjected to a range of loading scenarios in controlled laboratory environments. Post-failure, these structures were further tested using both cyclic and quasi-static loadings. Results shows that: repeated cyclic loading at safe working load levels do not significantly alter the ultimate load carrying capacity of virgin masonry arch structures; the residual strength of distorted and/or damaged arch structures can be significant; distorted and/or damaged bridges are to some extent able to heal when subjected to repeated cyclic loading at safe working load levels, which is not the case with a virgin arch. Based on these findings, it can be concluded that the safe working load and life span of distorted and/or damaged masonry arch structures must be established in conjunction with the current state of the masonry arch structure.