Trag Werk Ingenieure, Döking + Purtak Partnerschaft, Dresden, Germany


Primary concern while analysing the bearing capacity of Stone Vault Bridges is to estimate as realistic as possible the capacity of mostly historical valuable and robust structures and to support their conservation by cost-efficient restorations. Using the example of a natural stone bridge of ashlar masonry a new method has been developed. This method is based on bearing load curves. It is derived with the so called “Decoupled Discontinuum Model“.
On the basis of existing families of capacity curves the cross-section capacity of common natural stone masonry can be read off in consideration of the real geometry and material parameters. Bearing loads are determined at a Micromodel with non-linear material parameters. The Mohr-Coulomb failure criterion is used for stones. Under assumption of plastic characteristics of the mortar the Drucker–Prager yield criterion is used. The stress of the vault construction is displayed by calculation of the bearing surface with the stress path at the critical cross-section. The intersection point of the stress path and the design capacity curve yields to the utilisation factor of the construction (in comparison tothe needed partial safety factor).
The calculated collapse loads using the “Decoupled Discontinuum Model“ correspond well with experimental tests at the structures in full scale.

Key words
Discontinuum Model, bearing surface, cross-section bearing capacity, capacity curves, partial safety factor, load bearing test