CAPACITY OF MASONRY ARCHES AND SPATIAL FRAMES

A numerical model for the study of spatial structures consisting of cu rved, three-dimensional members with variable cross sections is presen ted, together with its application to the nonlinear geometric and mate rial analysis of skeletal masonry constructions. Nonlinear material be havior is included in the model by means of elastoplastic constitutive equations under shear and compressive stresses, while a linear-elasti c perfectly brittle behavior is assumed in tension. The dependency of shear strength upon the applied compression is taken into account by m eans of the Mohr-Coulomb failure criterion. Nonlinear geometric effect s caused by the imposition of the equilibrium condition upon the defor med configuration of the structure are considered, but it is assumed t hat the increments of both displacements and sectional rotations are m oderately small. Three examples are presented. The first is a circular helicoid formerly studied by Young and Scordelis (1958). A very good agreement and accuracy level were obtained, even though a very small n umber of elements, two or three, were used. The second example deals w ith the analysis of a masonry arch up to failure including nonlinear m aterial and geometric effects. Finally, the advantage of the presented formulation in the analysis of large structures is shown through the study of a Gothic vault.