A multidisciplinary approach to the mortars characterization from the Town Walls of Gubbio (Perugia,Italy)

Journal of Thermal Analysis and Calorimetry - In the frame of the HERACLES (HEritage Resilience Against CLimate Events on Site) project, a set of cultural heritage sites was studied to improve...     

Failure surface of quasi-periodic masonry by means of Statistically Equivalent Periodic Unit Cell approach

In this paper a homogenization procedure for the estimation of the failure surface of a quasi-periodic masonry, based on a mean stresses approach through the analysis of the Statistically Equivalent Periodic Unit Cell (SEPUC), is shown. The mean stresses approach consists in the identification of critical states for the homogenized continuum by means of an overall failure criterion, function of the mean stress state of each constituent. These macroscopic tensors are evaluated in the elastic field. The SEPUC definition refers to a statistical criterion applied to a population of Periodic Unit Cells generated taking into account the geometrical features of the quasi-periodic texture; moreover it is validated on the basis of the homogenized elastic properties in terms of components and Frobenius norm of the elastic matrix. By a multi-objective optimization approach, the obtained results highlight that the proposed SEPUC can be used to estimate the failure surface.     

Evaluation of a Statistically Equivalent Periodic Unit Cell for a quasi-periodic masonry

The paper presents a method to estimate the Statistically Equivalent Periodic Unit Cell (SEPUC) corresponding to a masonry with quasi-periodic texture. The identification of the texture and the constituent phases (unit blocks and mortar joints) is achieved by means of digital image processing techniques applied to color image of the masonry wall. A statistical analysis of geometrical parameters (width and height of blocks, thickness and length of mortar joints) allows to estimate their probability distribution and to identify the typology of the texture. Subsequently a Monte Carlo analysis is performed using several tentative SEPUCs generated with different dimensions of blocks and joints according to the estimated distributions. A criterion was eventually proposed to identify, among the numerically generated ones, the SEPUC which is more suitable to model the behavior of masonry wall. The SEPUC is analyzed with techniques available for periodic texture, applying periodic boundary conditions, in order to estimate the equivalent elastic stiffness. The proposed method is validated comparing the results in the elastic range obtained with SEPUC and those obtained imposing essential and natural boundary conditions on the original texture.     

On the graphic statics for the analysis of masonry domes

The graphic statics applied to constructions has been characterized by a rapid development between the end of the 19th century and the first decades of the 20th century. In this paper the application of the graphic statics to masonry domes is show. In particular three different methods are applied to a specific case study and the results discussed. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Strength domain of non-periodic masonry by homogenization in generalized plane state

This paper deals with the evaluation of the strength domain for non-periodic masonry using a random media micromechanical approach. The generalized plane state formulation is used in order to more accurately describe the masonry behavior and failure criteria proposed in literature. Considering the masonry as a heterogeneous material with random microstructure, the elastic characteristics of the homogenized continuum and the strength domain are evaluated by using the hierarchy theory related to partitions with increasing dimensions through the application of natural and essential boundary conditions with proportionally growing values. An overall failure criterion based on the mean stress state of each phase is introduced. The proposed procedure is validated by comparison with the experimental results obtained with periodic masonry subjected to biaxial stress states recovering the main failure mechanisms. Then the approach is applied to an actual non-periodic masonry introducing peculiar algorithms in order to evaluate strength surfaces and to verify the convergence of the domains obtained through the application of natural and essential boundary conditions with the increasing size of portion dimensions at the mesoscale level.