Limit Load and Collapse Mechanism of Spatial Arched Structures

A Finite Element Method (FEM) based model is presented that can be applied as a limit-analysis tool for spatial arched structures. A purely geometrical model can find the collapse mechanism of an arbitrary arched structure and the limit load which is the lower bound of the collapse load. The model takes into account the formation of new openings (cracks), which gradually reduce the initial stiffness of the structure, but does not consider sliding failure. The limit load is when the structure becomes a mechanism globally or locally. The effect of the discretisation and the residual torsional stiffness of an opened interface are investigated. The model is verified by planar and spatial examples applying the uniqueness theorem of Heyman. The results of the case study highlight the potential of the applied model: a very good approximation can be given of the collapse mechanism of a real 3D structure. The presented model can be used to evaluate existing or theoretical ribbed vault geometries. It can also be a powerful tool for earthquake assessment of historical arched structures as it gives the magnitude of the ground acceleration that transforms the structure into a mechanism.