2017
Software
Open Access

NOSA-ITACA is a code for the nonlinear structural analysis of historical masonry constructions. It the result of the integration of the finite element code NOSA into the open-source SALOME platform.

**See at: **
ISTI Repository | CNR ExploRA | www.nosaitaca.it

2017
Contribution to book
Closed Access

This chapter is devoted to comparing two numerical approaches for modelling the dynamic behaviour of masonry structures. The constitutive equation of masonry-like materials with bounded compressive strength and the dynamic problem for both three-dimensional bodies and one-dimensional structures are presented. The numerical methods implemented in the codes NOSA and MADY, respectively for three- and one-dimensional structures, are outlined. With the aim of comparing the two numerical procedures, two examples, a masonry tower with rectangular cross-section and a masonry arch, are addressed. The structures are subjected to their own weight and to three accelerograms recorded during real earthquakes. The comparison with the numerical results obtained assuming a linear elastic behaviour for the materials constituting the tower and the arch has stressed the importance of accurate constitutive models for masonry.

**See at: **
www.ctresources.info | CNR ExploRA

2014
Journal article
Open Access

The paper presents an efficient and reliable implementation of numerical methods for constrained generalized eigenvalue problems, specialized for the modal analysis of linear elastic structures in a finite-element setting. The implementation, which takes into account the sparsity of the stiffness and mass matrices and the features of master-slave constraints, is based on open-source packages embedded in the finite-element code NOSA-ITACA. Numerical tests on historical building are performed, with the aims of calculating their vibration frequencies and mode shape vectors, comparing them to the results of a general purpose commercial code and assessing the accuracy of the tool developed.

**See at: **
ISTI Repository | CALCOLO | Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna | link.springer.com | CNR ExploRA

2014
Conference article
Unknown

This paper describes the numerical modelling of the structural behaviour of the church of San Francesco in Lucca and the Rognosa Tower in San Gimignano. The constitutive equation of no-tension materials views masonries as nonlinear elastic materials with zero tensile strength and infinite or bounded compressive strength. As such equation has proven to be able to realistically model the most significant aspects of masonry's behaviour, it has been implemented in the finite element code NOSA-ITACA for solving static and dynamic problems of solids not withstanding tension. The numerical analyses of the church and the tower have been conducted via the NOSA-ITACA code. These case studies highlight the important role of numerical tools in assessing the mechanical behaviour of historical masonry buildings subjected to earthquakes, as well as in planning strengthening operations on such structures.

**See at: **
CNR ExploRA

2014
Software
Open Access

NOSA-ITACA is a code for the nonlinear structural analysis of historical masonry constructions. It the result of the integration of the finite element code NOSA into the open-source SALOME platform.

**See at: **
ISTI Repository | CNR ExploRA | www.nosaitaca.it

2013
Journal article
Open Access

An integrated simulation tool for multilayer stepped pyramidal structures is presented. The tool, based on a semi-analytical mathematical strategy, is able to calculate the temperature distributions and thermal stresses at the interfaces between the layers of such structures. The core of the thermal solver is the analytical simulator for power electronic devices, DJOSER, which has been supplemented with a mechanical solver based on the finite-element method. To this end, a new element is proposed whose geometry is defined by its mean surface and thickness, just as in a plate. The resulting mechanical model is fully three-dimensional, in the sense that the deformability in the direction orthogonal to the mean surface is taken into account. The dedicated finite element code developed for solving the equilibrium problem of structures made up of two or more superimposed plates subjected to thermal loads is applied to some two-layer samples made of silicon and copper. Comparisons performed with the results of standard finite element analyses using a large number of brick elements reveal the soundness of the strategy employed and the accuracy of the tool developed.

**See at: **
ISTI Repository | STRUCTURAL ENGINEERING AND MECHANICS | technopress.kaist.ac.kr | CNR ExploRA

2013
Contribution to conference
Open Access

The poster is devoted to the analysis of the numerical linear algebra issues arising in the modal analysis of structures with application to masonry construction of historical interest. Although the constitutive equation adopted for masonry is nonlinear, modal analysis gives important qualitative information on the dynamic behavior of masonry structures and allows for assessing their seismic vulnerability, while taking Italian regulations into account. Modal analysis consists in the solution of a constrained eigenvalue problem arising from the solution of the free vibration equilibrium equations in a finite-element setting and involves the mass and stiffness matrices and a set of constraints which enforce relationships between degrees of freedom. A simple example of a constraint, is the imposition of the Dirichlet boundary conditions which usually consists in setting certain degrees of freedom to zero (single-point or fixed constraints). A further example is given by the so called master-slave constraints which impose that the displacement of a node (called the slave) depends linearly on the displacements of other nodes (called the masters). These constraints are crucial, e.g., in modeling the contact interaction between masonry and reinforcement. We propose an efficient implementation of numerical methods for constrained eigenvalue problems, specialized for the modal analysis of structures taking into account both the sparsity of the matrices and the features of master-slave constraints. The implementation will be based on open-source packages embedded in the finite-element code NOSA-ITACA developed in the framework of a research project funded by the Region of Tuscany (www.nosaitaca.it/en/). Numerical examples will be shown on the Project case study "Voltone" - a large vaulted masonry structure located beneath Piazza della Repubblica in Livorno, Italy.

**See at: **
ISTI Repository | CNR ExploRA

2013
Conference article
Unknown

This paper describes the numerical modelling of the structural behaviour of the church of San Francesco in Lucca, Italy. The constitutive equation for the various types of masonry employed in historic buildings views masonry as a nonlinear elastic material with zero tensile strength and infinite or bounded compressive strength. As such an equation has proven to be able to realistically model the most significant aspects of masonry behaviour, it has been implemented in the finite element code NOSA-ITACA for solving equilibrium and evolution problems of solids not withstanding tension, as well as for modelling restoration and consolidation operations. Numerical analyses of the church of San Francesco have been conducted using the NOSA-ITACA code. The church, which dates back to the thirteenth century, presents evident fractures and deformations mainly due to the large dimensions of its nave. It has been studied under two different conditions: in its actual state and in the presence of reinforcement structures. In particular, an assessment has been made of the effects of a metal framework, applied atop the longitudinal walls, on the behaviour of the structure subjected to its own weight and horizontal actions modelling an earthquake. The case study described in the paper highlights the important role of mathematical models and numerical tools in assessing the mechanical behaviour of historical masonry buildings in the presence of earthquakes, as well as in planning strengthening operations on such structures.

**See at: **
CNR ExploRA

2013
Report
Unknown

The paper presents an efficient and reliable implementation of numerical methods for constrained generalized eigenvalue problems, specialized for the modal analysis of linear elastic structures in a finite-element setting. The implementation, which takes into account the sparsity of the stiffness and mass matrices and the features of master-slave constraints, is based on open-source packages embedded in the finite-element code NOSA-ITACA. Numerical tests on historical building are performed, with the aims of calculating their vibration frequencies and mode shape vectors, comparing them to the results of a general purpose commercial code and assessing the accuracy of the tool developed.

**See at: **
CNR ExploRA

2012
Contribution to conference
Open Access

NOSA-ITACA project, description of the case study

**See at: **
ISTI Repository | CNR ExploRA

2012
Report
Unknown

Research project "Structural analysis of the church of San Francesco in Lucca: modelling of some strengthening operations" - project report

**See at: **
CNR ExploRA

2012
Report
Unknown

Research project "Structural analysis of the church of San Francesco in Lucca: modelling of some strengthening operations" - project report

**See at: **
CNR ExploRA

2012
Conference article
Unknown

The paper presents a new numerical tool, the NOSA-ITACA code, for the structural analysis of masonry buildings of historical interest. The code, resulting from integration of the finite element code NOSA and the open-source platform SALOME, is being developed within the framework of the NOSA-ITACA project, funded by the Region of Tuscany. In this paper some preliminary results are described with the aim of illustrating the main features of the NOSA-ITACA code. After a short description of the constitutive equation used to model the mechanical behaviour of masonry constructions, some details are given concerning the code's implementation. Lastly, a dynamic analysis of the "Rognosa" tower in San Gimignano, performed via the NOSA-ITACA code, is presented to exemplify application of the code.

**See at: **
CNR ExploRA

2012
Conference article
Restricted

This paper deals with the results of some nonlinear dynamic analyses conducted via the finite element code NOSA on the "Rognosa" tower in San Gimignano. The NOSA code has been developed by the Mechanics of Materials and Structures Laboratory of ISTI-CNR and applied since the nineties to the study of many masonry buildings and monuments. The code models masonry as an isotropic, nonlinear elastic material with zero tensile strength and bounded compressive strength; thermal dilatations due to daily or seasonal thermal variations can be taken into account as well. The NOSA-ITACA project, funded by the Region of Tuscany for the years 2011-2013, is aimed at upgrading the NOSA code via the open source GUI platform SALOME and developing a technical support service to provide consultancy, assistance and training in the field of maintenance and restoration of the architectural heritage.

**See at: **
www.polistampa.com | CNR ExploRA

2011
Journal article
Restricted

In this paper, we consider the problem of the free longitudinal vibrations of a beam made of a bimodular material, i.e. an elastic material whose in-tension Young's modulus is a fraction of that under compression. After recalling the exact solutions for an infinite beam and for a beam with fixed ends calculated via the characteristics method, we apply high-resolution methods based on the finite-element approach to solve the nonlinear equation of the motion. In particular, we compare the exact solutions with the numerical solutions calculated using the collocation and least-squares method developed in the present study, the space-time element method, as well as total variation diminishing (TVD) and Newmark methods.

**See at: **
International Journal of Structural Stability and Dynamics | www.worldscientific.com | CNR ExploRA

2011
Journal article
Restricted

The DJOSER analytical thermal solver for multilayer mounting structures has been tested as a useful and friendly tool for the thermal analysis of power electronic devices and their packages, able to replace the onerous programs based on the finite element method (FEM) calculations. The other problem connected with the packaging evaluation is the calculation of the thermally induced stresses and strains in the various layers composing the assembling structures. This paper deals with the first step of the implementation of a thermomechanical solver to be connected with the DJOSER program, which is able to calculate the stresses at the layer interfaces, using the same strategy, i.e., a semianalytical mathematical approach, as well as the same structural models (stepped pyramidal structures and homogeneous layers). The basic theory is briefly exposed and the method is applied to some two-layer virtual structures. The obtained results are compared with those obtained using standard FEM analyses.

**See at: **
asmedl.org | Journal of Electronic Packaging | CNR ExploRA

2011
Conference article
Unknown

In this paper, by limiting the treatment to thermomechanical uncoupling, we study the behaviour of masonry-like materials and analyse the influence of the temperature dependence of the Young's modulus on the stress field and crack distribution in a spherical container subjected to internal and external uniform radial pressures and steady temperature distributions. If the Young's modulus E does not depend on temperature, the solution to the equilibrium problem can be calculated explicitly. Instead, when E depends on temperature, the solution is calculated numerically via the finite element code NOSA. The solutions corresponding to constant and temperature-dependent Young's moduli are compared, and the influence of the temperature dependence of E on the specific heat is assessed.

**See at: **
CNR ExploRA

2011
Contribution to conference
Open Access

The paper presents a new numerical tool, the NOSA-ITACA code, for the structural analysis of masonry buildings of historical interest. The code, resulting from integration of the finite element code NOSA and the open-source platform SALOME, is being developed within the framework of the NOSA-ITACA project, funded by the Region of Tuscany. In this paper some preliminary results are described with the aim of illustrating the main features of the NOSA-ITACA code. After a short description of the constitutive equation used to model the mechanical behaviour of masonry constructions, some details are given concerning the code's implementation. Lastly, a dynamic analysis of the "Rognosa" tower in San Gimignano, performed via the NOSA-ITACA code, is presented to exemplify application of the code.

**See at: **
ISTI Repository | CNR ExploRA

2011
Report
Unknown

Project Report "Development of the NOSA-GRAPH code for the structural analysis of masonry buildings of historical and architectural interest". Funded by the Fondazione Cassa di Risparmio di Lucca, 2010-2011

**See at: **
CNR ExploRA

2010
Conference article
Closed Access

An integrated simulation tool for multilayer stepped pyramidal structures, able to calculate the temperature distributions and thermal stresses at the interfaces between the layers and based on a semi-analytical mathematical strategy is presented. The core of the thermal solver is the analytical simulator DJOSER for power electronic devices. DJOSER is then integrated with a mechanical solver based on the finite element method. A new element is proposed whose geometry is defined by its mean surface and thickness, just like in a plate, and whose mechanical behaviour is fully three-dimensional, in the sense that the deformability in the direction orthogonal to the mean surface is taken into account. The dedicated finite element code developed for solving the equilibrium problem of structures made up of two or more superimposed plates subjected to thermal loads is applied to some two-layer samples made of silicon and copper. The comparisons with the results of standard finite element analyses using a large number of brick elements are presented and discussed. © 2010 IEEE.

**See at: **
doi.org | CNR ExploRA