Vincenzo Mallardo

A NURBS boundary-only approach in elasticity

An improvement to the classical application of the isogeometric approach to the two-dimensional boundary element method is proposed. In the classical isogeometric approach the boundary conditions are imposed directly to the control variables that are not always interpolatory of the governing variables, thus introducing an error that may also be large. The issue has been debated in the finite element method context where it has recently motivated various alternative techniques, but it is still open in other numerical methods. In the present paper the approach, introduced by the authors in a previous paper, to correctly impose any general boundary condition in the boundary element method framework, is theoretically and numerically investigated. Comparison with analytical solutions, classical boundary element solutions and isogeometric boundary element solutions are carried out to demonstrate the improved performance of the proposed approach.

Crack Patterns Induced by Foundation Settlements:Integrated Analysis on a Renaissance Masonry Palace in Italy

This study presents some numerical results related to the analysis of the structural damage of a historic masonry building, Palazzo Gulinelli, in Ferrara, Italy. A detailed analysis of the inhomogeneities of the facade, historic documentation, and recent restoration interventions carried out in an adjacent building, suggest that the Palace underwent various modifications both on the structural configuration and on the borne loads. Such modifications might be the main cause of some differential settlements and of the consequent significant crack pattern on the load-bearing walls. Therefore, in the present paper the occurrence of a crack pattern on the facade is simulated by carrying out standard linear and non-linear finite element (FE) homogenized models; differential settlements are applied in order to reproduce the structural changes occurred over time. Previous experiences of the authors (for example, Acito and Milani in 2012 and Mallardo et al. in 2008), the current crack pattern of the building (of its facade in particular) and the monitoring data referring to some of them are the main references for the analysis carried out. The structural survey, the numerical results, and the data monitoring suggest two main conclusions: 1) a good correlation between numerical results and monitoring data is assessed, therefore the cracks can be reasonably related to past differential settlements; and 2) the cracks/damage that occurred as a consequence of differential foundation settlements reduce the ability of the facade to resist seismic actions.

A NURBS-BEM Application in Continuum Damage Mechanics

In this paper the integral equation approach is used to describe the propagation of continuumdamage in three dimensional solids. The governing equation is of integral type and contains bothboundary and domain integrals. Such integrals are computed with the aid of the NURBS functions.The subvolume involved by the damage is modelled by a special mapping procedure that avoids theuse of the internal cells. The implementation is verified on a test case for which an analytical solutionis available.

An enhanced exponential matrix approach aimed at the stability of piecewise beams on elastic foundation

In this paper, an enhanced exponential collocation method for the stability assessment of piecewise beams resting on elastic foundation and subjected to both non-uniform distributed and concentrated loads is presented. The exponential basis functions usually adopted in literature are enriched with trigonometric functions that make the eigenvalue analysis well-posed without reducing the original simplicity of the method. A measure of the error occurring from the proposed approach and its improvement are also proposed. Several examples aimed at estimating the buckling loads under typical end supports are discussed. A comparison with exact and with other numerical results that are available in literature are carried out. Such a comparison shows the high accuracy and the fast convergence of the proposed approach.