Automatic assessment of partial failure mechanisms in retrofitted historical masonry aggregates through adaptive nurbs limit analysis

The aim of this work is to propose a new automatic procedure for the seismic assessment of partial failure mechanisms in historical masonry aggregates. Starting from the geometrical survey, a three-dimensional model of the whole aggregate is derived. The model is discretized through few NURBS surfaces (Non-Uniform Rational Bezier Spline) and imported into the MATLAB environment. A procedure of kinematic limit analysis is applied to a preselected part of the construction. The walls selected are subdivided into few elements, each one is a portion of the initial NURBS surface and is assumed as a rigid body. Rigid-plastic interfaces are defined on the boundary of each element. As a result, the kinematic limit analysis provides a local mechanism involving the selected walls and an associated kinematic multiplier. An optimization procedure, here conducted by using a Genetic Algorithm, is applied with the aim of finding the collapse multiplier. The procedure can take into account the most spread reinforcement techniques adopted in historical constructions, such as tie-rods and FRP strips, which maintain a local response to horizontal loads. An application to a historical masonry aggregate, located in the center of Arsita (Teramo, Italy), is finally presented.