A case study on the influence of mechanical properties on the collapse load of stone arch bridges

摘要

In this paper, the determination of the collapse load of an historical stone arch bridge situated in the Northwest of Spain is accomplished. The arch presents damage and its load bearing capacity is reduced, so repair works and restoration are needed. In such circumstances, the assessment of the ultimate load that the bridge can support is very important and so the limit analysis method is applied, which delivers the collapse load and the failure mechanism considering the hypothesis of plastic collapse of the structure. On the other hand, and taking into account that one of the major drawbacks in the analysis of this type of bridge is the lack of accurate data about material properties, a parametric study is performed selecting from all the mechanical parameters governing the bridge response, those with a wider range of variation or those having a more difficult characterization: masonry and backfill unit weight, compressive strength of the masonry, coefficient of radial friction between voussoirs, height of backing, earth pressure coefficient and load dispersion model. For each one of the properties considered, five values are selected, based upon recommendations found in technical literature or in previous experiences with similar bridges, and a series of analyses are performed, obtaining the influence line of kinematic safety factor, with respect to live load, and the critical failure load variation, with respect to each one of the material properties. Results show that the most significant properties having influence in the collapse load are the compressive strength of the masonry, the earth pressure coefficient and the unit weights of materials.