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In this contribution, the modelling of salt crystallization-induced damage in layered porous materials (such as masonry strengthened with composites, glazed earthenware, etc.) is addressed through a staggered multiphysics method. A staggered interchange of data is pursued between a multiphase model (crystallization pressure) and a macro-scale nonlinear mechanical model (material damage). Such method is preliminary applied to layered porous materials through a simple benchmark. Accordingly, the effects of layers with different properties on the crystallized salt distribution and damage pattern are highlighted.

The health emergency caused by the spread of Covid-19 had a profound effect on higher education institutions, forcing them to promptly move all academic activity online. The University of Bologna (Unibo) promptly switched to distance mode to ensure continuation of its services, projects and activities. This situation required, and still requires strong academic commitment and co-ordination among the different actors involved and an increasing investment in innovation of teaching and learning processes, mobilising the university system at several levels and increasing the importance of research-based activities.

In this paper, a staggered multiphysics framework is proposed for the numerical simulation of salt crystallization-induced damage in porous building materials, such as masonry. This staggered framework is based upon a multiphase model to account for salt transport and crystallization within the porous material and a plastic-damage model to account for the nonlinear mechanical behavior of the material. The staggered structure is composed of a two-way data exchange between the multiphase and the mechanical models. Firstly, crystallization pressure information is passed to the mechanical model to analyze the mechanical response of the material. Secondly, the mechanical outcomes (e.g. damage distribution) are used to update some multiphase model properties (e.g. tortuosity) allowing simulations also beyond the onset of damage. Few simple geometry-based relationships are discussed to update multiphase model properties along with damage. Numerical examples are used to show the capability of the proposed staggered framework for simulating complex interactions among salt transport, salt crystallization, and damage within the porous material, highlighting the possibilities of this modeling approach to conduct simulations also beyond the onset of damage.

Questo contributo presenta, in sintesi, il progetto di sistema per l’innovazione della didattica universitaria che l’Università di Bologna sta realizzando. Si tratta di un progetto ampio, orientato dall’idea che la formazione universitaria debba prioritariamente promuovere, per tutti gli studenti e le studentesse, competenze intese come entità complesse, che integrano le conoscenze, le abilità, gli elementi metacognitivi, le competenze trasversali strategiche per l’apprendimento e per la vita. Il progetto pone al centro le competenze didattiche del docente e si propone di incidere su molteplici livelli e dimensioni dei processi di insegnamento-apprendimento, in una prospettiva diacronica. In particolare, il progetto trae la sua cornice teorico-metodologica dal modello della Formative Educational Evaluation (Scriven, Stufflebeam, Stake, Lincoln, House e Howe in Kellaghan e Stufflebeam, 2003; Bondioli, Ferrari, 2004) e, in particolare, della Ricerca-Formazione intesa in senso valutativo (Betti, Vannini, 2013; Betti, Davila, Martínez, Vannini, 2015, Asquini (CRESPI) 2018). L’applicazione del modello ai contesti didattici dell’Università di Bologna ha potuto beneficiare di due esperienze pilota di ricerca valutativa realizzate all’interno dell’Ateneo con i docenti dei Corsi di laurea in “Infermieristica” e in “Economics and Finance” (CLEF); nella logica della formative educational evaluation, il modello bolognese contempla azioni valutative orientate specificamente in senso formativo (di analisi e progressiva ri-progettazione delle azioni didattiche supportata da interventi formativi ad hoc rivolti ai docenti) che promuovano nei docenti capacità di riflessione e autoanalisi delle proprie prassi didattiche, specifiche azioni di formazione alla didattica attraverso metodologie innovative e l’uso delle tecnologie.

With 86,509 enrolled students, and personnel over 5500 units (University of Bologna 2018), the University of Bologna, one of the most ancient Western higher education institutions was established in 1088 A.D. (University of Bologna 2017a) and, located in a middle-sized town of Northern Italy, faces daily challenges in a constantly evolving society with continuously changing paradigms. At Alma Mater, a multi-campus structure with over 1,162,506 m2 of facilities only in Europe placing the University as the first European university for international mobility with 2787 outbound students and 1970 inbound students in 2018 (INDIRE 2019). This geographic spread and other factors require a broad and long-term vision of the governance strategy, which goes side by side with the central activities of researching and training in full respect of the freedoms of science and teaching, as it is stated at Art. 3.1 of the University Statute (Italian Republic 2011). The considerable human and physical of the University system lead to both the need and the duty to harmonize the relationship within people, between people and the environment—that is, between the University and all its stakeholders. Recognizing its role in the society and willing to be a positive actor of change, combining innovation with the history that it has consolidated over time, the Alma Mater Studiorum is fully aware that its activities can produce a significant impact, both direct and indirect, on the community and in the region

The flow field around the rectangular cylinder with aspect ratio 5:1 has been widely investigated in recent literature as a prototype of reattached flow around elongated bluff bodies like bridge decks and high rise buildings. Due to the technical importance of such flows, many research works have been proposed aiming at studying the accuracy of available simulation techniques in reproducing the flow organization. When Large Eddy Simulations (LES) are considered, to the authors’ knowledge, the proposed contributions focused on perfectly smooth inlet conditions which, indeed, represent more an exception than a rule in Computational Wind Engineering. In the present paper, LES are performed aiming at reproducing the modifications occurring in the flow when turbulent inflow conditions are adopted. In order to synthetically produce the unsteady inlet condition, a divergence-free and spatially correlated fluctuations field is generated by means of the Modified Discretizing and Synthesizing Random Flow Generator technique. The obtained synthetic fluctuations are imposed in the computational domain by modifying the velocity-pressure coupling algorithm in order to avoid nonphysical pressure fluctuations. Two configurations, corresponding to mild and strong incoming turbulence levels, are investigated highlighting the role played by the spanwise domain size. Results are compared to experimental data showing good agreement between experiments and numerical simulations.

In this paper, an innovative numerical modeling strategy for the structural analysis of historical monumental buildings is presented. The strategy is based on a procedure that enables the semi-automatic transformation of a three-dimensional points cloud surveyed through terrestrial laser scanner or closed range photogrammetry into a three-dimensional finite element mesh, as well as its mechanical characterization. Therefore, an increase of the level of automation in the mesh generation process is attained and a large reduction in the required time in comparison with traditional modeling procedures is achieved. In order to validate the new strategy, an application to the case study of the San Felice sul Panaro (Italy) fortress is carried out. The reliability of the proposed model is assessed through a comparison between the results of structural analyses and the crack pattern experienced by the structure during the Emilia earthquake (2012). Moreover, the vulnerability assessment of the main tower of the fortress is performed through simplified pushover analyses conducted on the generated mesh.

During the G7 Environment Ministerial Meeting under the Italian Presidency which took place in Bologna, Italy, 11–12 June 2017, representatives from Universities and Research Institutes and from the major industries of the G7 countries joined two Ministerial side events to identify current and future priorities for implementing Sustainable Development (SD) in the G7 countries. This article is built on materials produced in both side events with the aim of deepening the role of universities for SD. The major findings of the G7 Environment Ministerial Meeting are presented, with a focus on sustainable teaching and learning, university research for SD and effective cooperation between universities and industries. The recommendations have more general implications for the role of universities in addressing public policies. Universities have the core responsibility to promote a systemic approach in relation to the multiple societal challenges and to influence policy makers, but the leadership for SD implies the ability to build partnerships with other universities and networks of shared value with all relevant stakeholders of SD.

In this work, the post-buckling analysis of thin-walled beams by using the Generalized Beam Theory (GBT) is presented. To this purpose, a geometrically nonlinear GBT finite element is developed by exploiting the features of mixed-stress GBT finite element formulation in the framework of the Implicit Corotational Method (ICM). The application of the ICM to GBT is briefly discussed and the details necessary to successfully transform the linear GBT finite element in its nonlinear counterpart are illustrated. The numerical results show how the proposed finite element can deal with global and distortional geometrically nonlinear phenomena, in good accordance with respect to 3D shell models.

Semi-rigid rockfall protection barriers are steel structures constituted by a principal interception structure made of cables mounted on structural steel posts fully restrained to the ground. Traditionally, they are assigned a low capacity value which ranges from few to less than 300 kJ. Over the last decades, semi-rigid rockfall protection barriers have been installed along areas interested by rockfall events, often in conditions of extreme urgency, without a specific structural design. As a result, they are found in a variety of subtypes, most of them lacking the essential structural information, such as the energy absorption capacity, crucial for a reliable application of procedures for quantitative risk assessment. To fill this gap, and considered the lack of experimental data on semi-rigid barriers, in the present study a numerical investigation of the most common barrier subtypes is developed. In the absence of standards for this kind of barriers, the barriers are virtually tested in conditions inspired by the essential prescriptions included in the European Guideline for flexible barriers (ETAG 27). Results allow to: (i) investigate the performance of the barriers in service condition; (ii) provide an estimate of the barrier capacity and (iii) explore the barrier failure mode.

In this paper we present the study of an archaeological structure in Pompeii and we detail the difficulties encountered applying the Italian standards and guideline when designing the new roofing structure. Following the latest Italian standards and guidelines, about the assessment and mitigation of seismic risk of cultural heritage, the analysis of the Insula has been carried out. In particular, among all the studied structures, the attention was focused on the covering of the main hall where a prototype of a roofing structure covering a portion of the hall was installed near the remaining ruins of the house. Numerical models have been developed in order to track the effect of these new roofing structures on this ancient masonry structure.

We propose a computational approach to study the response of compliant structures to impulsive loading due to impact on the free surface of a weakly compressible viscous fluid. The fluid flow is analyzed through the lattice Boltzmann method and the structural response by the finite element method. The time discontinuous Galerkin method is used to integrate the structural dynamics in time, and an explicit coupling strategy with the same time-step for the fluid and the solid is employed. Numerical results are compared to analytical and experimental findings for rigid and compliant wedges.

In this paper, the flow around a rectangular cylinder with aspect ratio 5:1 is studied at three attack angles by means of both LES and URANS simulations. Despite its geometric simplicity, such a rectangular shape is characterized by many aerodynamic phenomena typical of reattached flows around bluff bodies and has been recently widely studied as a prototype of flows encountered around shapes of technical interest like, for example, bridge deck sections. The present study is aimed at providing insight in the modifications occurring in the flow at small incidence angles, by comparing the accuracy of the two aforementioned simulation strategies in reproducing them. Some recurring biases observed in URANS simulations are illustrated and their origin discussed. Results are presented in terms of flow bulk parameters and pressure distributions and systematic comparison with available experimental data is provided. Finally, the effects of small incidence angles on along span flow correlations are investigated and Covariance Proper Transformation is used in order to further characterize the flow dynamic behavior.

This paper is motivated by the concept that the successful, effective, and sustainable implementation of the smart city paradigm requires a close cooperation among researchers with different, complementary interests and, in most cases, a multidisciplinary approach. It first briefly discusses how such a multidisciplinary methodology, transversal to various disciplines such as architecture, computer science, civil engineering, electrical, electronic and telecommunication engineering, social science and behavioral science, etc., can be successfully employed for the development of suitable modeling tools and real solutions of such sociotechnical systems. Then, the paper presents some pilot projects accomplished by the authors within the framework of some major European Union (EU) and national research programs, also involving the Bologna municipality and some of the key players of the smart city industry. Each project, characterized by different and complementary approaches/modeling tools, is illustrated along with the relevant contextualization and the advancements with respect to the state of the art.

In this paper, a systematic approach to couple the lattice Boltzmann and the finite element methods is presented for fluid–structure interaction problems. In particular, elastic structures and weakly compressible viscous fluids are considered. Three partitioned coupling strategies are proposed and the accuracy and convergence properties of the resultant algorithms are numerically investigated together with their computational efficiency. The corotational formulation is adopted to account for structure large displacements. The Time Discontinuous Galerkin method is used as time integration scheme for structure dynamics. The advantages over standard Newmark time integration schemes are discussed. In the lattice Boltzmann solver, an accurate curved boundary condition is implemented in order to properly define the structure position. In addition, moving boundaries are treated by an effective refill procedure.

Twin box decks are becoming increasingly adopted in long span bridges due to their good aerodynamic performance with respect to the flutter instability. For small gaps between the decks they behave as a whole continuous body while, increasing the gap, strong dynamic interaction between the two occurs: the windward deck causes a turbulent wake that impinges on the leeward girder inducing unsteady aerodynamic forces. This complex behaviour makes the simulation of the aerodynamics of these structures a challenging task from the Computational Fluid Dynamic point of view. In this context, the present paper aims at investigating the capabilities and limitations of RANS and LES based simulations in reproducing the flow field organization around a twin box deck section. Different configurations, with increasing separation gap, are studied and compared with experimental data. Finally, the effects induced by the presence of barriers is investigated for the largest separation gap.

In this paper, a novel approach to the determination of Equivalent Static Wind Loads is presented. The envelope of the effects on the structure, representing the design load for each structural member and obtained by means of a complete buffeting analysis, is reconstructed, in a least square sense, by considering a series of statically applied load conditions. Such load conditions are obtained by combining Principal Static Wind Loads which, in turn, are obtained by means of the recently introduced Proper Skin Modes. By considering a smoothed version of the maximum/minimum operator, efficient, gradient based, optimization algorithms can be used in order to drive the least square minimization which conduces to the identification of the most significant wind load conditions. Such load conditions, statically applied, can be used in order to fully characterize the effect of the wind on the structure with very good approximation. No hypotheses are introduced regarding the shape of the envelopes, so rendering the procedure of general applicability. Very good results in terms of reconstruction rate and accuracy are obtained on a low-rise and a high-rise buildings.

Equivalent Static Wind Loads (ESWLs) represent an extremely useful tool for the characterization of the structural response to the wind action and provide a convenient way for structural engineers in order to include the results of a complete, rigorous, buffeting analysis in the design process. Recently, a novel approach to the determination of ESWLs has been proposed which is based on the adoption of Proper Skin Modes for the characterization of the static/quasi-static structural response. In that study, the reconstruction of the extreme internal forces over the structure for all structural members has been performed in a least square sense and a smoothed version of the maximum/minimum operators, typical of envelope calculations, has been adopted. By using such formulation, it is possible to use efficient, gradient-based, optimization techniques in the minimization procedure which leads to the identification of ESWLs. In this paper, two refinements of the original technique are proposed: the least square approach is modified in order to ensure a complete covering of the envelope and the original formulation is extended in order to take into consideration the contemporaneity between effects. Finally, the proposed approach is tested on a large span suspended roof derived from the structural model of the New Juventus Stadium showing extremely encouraging results.

The possibility to establish clear relationships between the results of the Generalized Beam Theory (GBT) and those of the classical beam theories is a crucial issue for a correct theoretical positioning of the GBT within the other existing beam theories as well as for the application of the GBT in the current engineering practice. With this in mind, the recovery of classical and non-classical beam theories within the framework of the GBT is presented in this paper. To this purpose, a new formulation of the GBT with shear deformation is conceived. Particularly, the formulation recently proposed by the authors is here modified by introducing new definitions of the kinematic parameters and of the generalized deformations, and extended to the dynamic case. Firstly, it is shown that a suitable choice of the flexural deformation modes allows recovering the Vlasov beam theory, both with and without shear deformation. Also, the analytical solution of the non-uniform torsion problem with shear deformation is given. Then, the recovery of the Capurso beam theory using the nonlinear warping deformation modes is illustrated.

In this paper, the ability of two RANS-based turbulence models, the standard k – ω and the k – ω sst (shear-stress-transport formulation), in predicting flutter derivatives of elongated rectangular prisms with different aspect ratios is investigated. Strengths and limitations of the employed methodology are highlighted via comparisons with available experimental results, aiming at identifying some operative indications for choosing a suitable modeling approach (not much time-consuming and suitably accurate), useful for engineers facing the aerodynamic design of bridge structures. The influence of discrepancies among experimental measurements and RANS-based numerical results on the aeroelastic stability of bridge-like structures is also discussed.

A recent study [1] has discussed the accuracy of the nodal elastic stresses of zero thickness interface elements when fictitious elastic parameters (often called penalty stiffness factors) are used. These stresses, commonly used to calculate the triggering conditions of the opening of the interface simulating a discrete crack in quasi-brittle materials, are affected by non-negligible errors if the in- terfaces are embedded in unstructured/irregular meshes. A procedure to avoid these errors has been proposed for homogeneous materials [1] and bi-material interfaces [2]. Accurate nodal stresses are re- covered if certain geometry-dependent pre-processed coefficients are used. In this paper, this method is proposed in the analysis of Historical Stone Masonry Walls: zero-thickness interface elements rep- resent the interaction between stones of irregular shape. The crack opening triggering conditions are calculated for two identical meshes with rigid continuous elements representing the stones and fic- titiously elastic zero-thickness interfaces representing the mortar layers. This paper shows that the use of the proposed coefficients significantly changes the values of the interface stresses leading to different configurations of the cracking onset.

The present paper develops a refined and general three-dimensional phenomenological constitutive model for shape memory alloys (SMAs), along the lines of what recently proposed by Auricchio and Bonetti (2013) in a more theoretical context. Such an improved model takes into account several physical phenomena, as martensite reorientation and different kinetics between forward/reverse phase transformations, including also smooth thermo-mechanical response, low-stress phase transformations as well as transformation-dependent elastic properties. The model is treated numerically through an effective and efficient procedure, consisting in the replacement of the classical set of Kuhn-Tucker inequality conditions by the so-called Fischer-Burmeister complementarity function. Numerical predictions are compared with experimental results and the finite element analysis of a SMA-based real device is described to assess the reliability of the proposed model as well as the effectiveness of its numerical counterpart.

In this paper, a numerical tool able to solve fluid-structure interaction problems is proposed. The lattice Boltzmann method is used to compute fluid dynamics, while the corotational finite element formulation together with the Time Discontinuous Galerkin method are adopted to predict structure dynamics. The Immersed Boundary method is used to account for the presence of an immersed solid in the lattice fluid background and to handle fluid-structure interface conditions, while a Volume-of-Fluid-based method is adopted to take trace of the evolution of the free surface. These ingredients are combined through a partitioned staggered explicit strategy, according to an efficient and accurate algorithm recently developed by the authors. The effectiveness of the proposed methodology is tested against two different cases. The former investigates the dam break phenomenon, involving the modeling of the free surface. The latter involves the vibration regime experienced by two highly deformable flapping flags obstructing a flow. A wide numerical campaign is carried out by computing the error in terms of interface energy artificially introduced at the fluid-solid interface. Moreover, the structure behavior is dissected by simulating scenarios characterized by different values of the Reynolds number. Present findings are compared to literature results, showing a very close agreement.

A survey of several methods under the heading of strong formulation finite element method (SFEM) is presented. These approaches are distinguished from classical one, termed weak formulation finite element method (WFEM). The main advantage of the SFEM is that it uses differential quadrature method (DQM) for the discretization of the equations and the mapping technique for the coordinate transformation from the Cartesian to the computational domain. Moreover, the element connectivity is performed by using kinematic and static conditions, so that displacements and stresses are continuous across the element boundaries. Numerical investigations integrate this survey by giving details on the subject.

The present study aims at providing an overview regarding the level of knowledge and experience gained about nanomodified surface treatments in the context of historical buildings and monuments. Nowadays, nanotechnology offers a variety of interesting cues for research, having a potential impact on every domain of science and technology. In particular, with regard to the area of surface treatments and their use in the field of historic buildings preservation, evolutionary changes may be expected. Optimized tailor-made materials and films, with previously non-achievable properties, can now be produced due to the gained ability in creation, manipulation, modeling and characterization of nanostructured systems. However, health and environmental protection issues should be considered.

Experimental and numerical results show that the predominant failure mode of FRP strengthened masonry structures is the interfacial debonding, which occurs prior to reaching the compressive strength of the substrate and/or the tensile strength of the FRP composite. In this paper, a three-dimensional numerical model is developed to simulate the experimental response of direct shear test applied to a FRP sheet on the masonry substrate. A damage model is adopted for both mortar and bricks characterized by different behavior in tension and compression.

This paper concerns the capabilities and the limitations of computational fluid dynamic simulations in evaluating the dynamic aeroelastic coefficients currently used to study the bridge deck instability due to wind loading. The attention is focused on the Reynolds-averaged Navier-Stokes (RANS) approach coupled with the k − ω turbulence model, identified as the best compromise between accuracy and computational cost. Firstly, the capabilities of the turbulence model to evaluate the aerodynamic forces acting on static bluff bodies are assessed. Then, the static and dynamic aerodynamic coefficients of the Great Belt East Bridge cross-section are evaluated, and the performances of three widely used turbulence models are compared. Aiming at providing a well-defined modus operandi useful for structural engineers who approach computational flutter derivatives estimation, much attention is devoted to detail the setting of the numerical analyses as well as the interpretation of the results and the comparison to wind tunnel data.

A new formulation of the Generalized Beam Theory (GBT) that coherently accounts for shear deformation is presented in this paper. In particular, a modified formulation of the kinematics early proposed by Silvestre and Camotim for shear deformable GBT is devised. The new formulation, which preserves the general format of the original GBT for flexural modes, introduces the shear deformation along the wall thickness direction besides that along the wall midline, so guaranteeing a coherent matching between bending and shear strain components of the beam. According to the new kinematics, a reviewed form of the cross-section analysis procedure is devised, based on a unique modal decomposition for both flexural and shear modes. Much attention is posed on the mechanical interpretation of the deformation parameters in the modal space. It is shown that, in the modal space, it is possible to clearly distinguish bending deflections from deflections due to shearing strains, and to recover classical beam degrees of freedom and standard beam theories as special cases. The effectiveness of the proposed approach is illustrated on two typical benchmark problems.

A numerical approach has been recently devised by the authors for the modelling of falling rock protection barriers, metallic structures used as passive measures against rockfall. Following this approach, in this study a FE model of a specific barrier type is developed. The constitutive parameters of the model are calibrated employing the data of a series of experiments carried out onto the main barrier components such as the interception structure and the energy dissipating devices. Then, the ability of the FE model to reproduce the real barrier behaviour is explored by simulating, retrospectively, a set of experiments carried out onto real-scale prototypes of the barrier, under various impact conditions. The very good fit of the rather complex experimental and numerical results can assess the ability of the FE model to reproduce the prototype behaviour, so validating the reliability of the adopted numerical approach and giving further confidence to the use of such models as design tools. Therefore, based on the numerical results, the considered barrier model has been enhanced in terms of cost-effectiveness and on-site performance.

The paper deals with geometrically nonlinear finite element analysis of folded-plate and shell structures. A Koiter asymptotic approach is proposed, based on the reuse of a linear element in the nonlinear context through a corotational formulation.The corotational approach represents a simple and effective way to satisfy the basic requirement of Koiter analysis, i.e. full objectivity in the finite element modeling. In fact, starting simply from a suitable linear finite element and implementing the corotational algebra proposed in Garcea et al. (2009), Zagari (2009) lead to objective explicit expressions for the first four variations of the strain energy which are needed by asymptotic analysis.The shell element used here is the flat shell quadrangular element with 4 nodes and 6 dofs per node proposed in Madeo et al. (2012) and called MISS-4: a mixed element, based on the Reissner–Mindlin plate theory, with an Allman-like quadratic interpolation for displacements and an equilibrated isostatic interpolation for the stress resultants. The element is free from locking and spurious zero-energy modes, so it appears a suitable candidate for nonlinear corotational analysis.The results of the numerical validation show the effectiveness and accuracy of the proposed approach, and its excellent overall robustness for both mono- and multi-modal buckling problems, also in the presence of strong nonlinear pre-critical behavior.

This paper focuses on a computational approach for nearly incompressible viscous fluids interacting with slender elastic structures. The lattice Boltzmann method is used to predict fluid dynamics and the corotational finite element formulation together with the time Discontinuous Galerkin method to predict structure dynamics. The coupling strategy is explicit and the fluid–structure interface conditions are handled by the Immersed Boundary method. A wide numerical testing proves the effectiveness of the proposed approach and its advantages with respect to similar strategies implementing the bounce-back scheme to enforce interface conditions.

In this paper, the interpolated bounce-back scheme and the immersed boundary method are compared in order to handle solid boundary conditions in the lattice Boltzmann method. These two approaches are numerically investigated in two test cases: a rigid fixed cylinder invested by an incoming viscous fluid and an oscillating cylinder in a calm viscous fluid. Findings in terms of velocity profiles in several cross sections are shown. Differences and similarities between the two methods are discussed, by emphasizing pros and cons in terms of stability and computational effort of the numerical algorithm.

The numerical modeling of historical monumental buildings is a challenging task for contemporary civil engineers. One of the main reasons for this is that the use of traditional simplified structural schemes is inadequate due to the complex geometry of such historical structures. Therefore, it is necessary to resort to a fully 3D modeling technique that is performed using Computer Aided Design (CAD). In general, CAD-based modeling is an expensive and complex process and it is often performed manually by the user, which inevitably leads to the introduction of geometric simplifications or interpretations. In this study, an innovative mesh generation approach for the structural analysis of historical monumental buildings is presented. The method consists in a peculiar breakdown of the geometry starting from laser scanner or photogrammetric surveys. Moreover, this new approach involves a structural discretization that guarantees the generation of 3D finite element meshes as well as their mechanical characterization. The most relevant feature of the proposed method is the possibility to directly exploit 3D and detailed point clouds surveyed on historical buildings for structural purposes. As a result, a large reduction in the required time in comparison to CAD-based modeling procedures is achieved. A geometrical and structural validation of the method is carried out on a masonry tower application. The findings show good reliability and effectiveness of the mesh generation approach.

A well known peculiarity of the structural response to wind loading is that static, quasi-static and resonant effects are present, in general, without a clearly dominant contribution. In such conditions, the calculation of wind effects would require to consider a large number of modes due to the relevant contribution of high frequency ones. In the present paper, in order to alleviate inaccuracies in the evaluation of static and quasi-static effects, induced by the truncation of the modal base, an efficient approach to the evaluation of static and quasi-static corrections is developed. To this purpose, a new class of pressure modes, called Proper Skin Modes (PSMs), is introduced and the corrections are evaluated based on the structural response to such modes, statically applied. PSMs can be seen as a novel modal version of traditionally adopted influence coefficients and naturally arise from the adopted pressure interpolation technique. The obtained approach is compact and efficient leading to a reduced data exchange between structural and wind engineers and to an optimal organization of the software used to perform the analyses. The proposed procedure is tested on a low-rise and a high-rise building showing very good performances.

Preliminary results of a Large Eddy Simulation (LES) of rectangular cylinder performed with Open Foam are presented. This is the preliminary part of a longer research project aimed at systematically study the ability of Computational Fluid Dynamics (CFD) techniques in reproducing the flow around slender bodies with sharp edges at high Reynolds numbers. In spite of the simple geometry, the problem is influenced by a number of parameters which makes its correct solution difficult to be achieved. The LES approach presented here appears to be a good candidate for this purpose but further analysis must be performed. Indeed, we highlight the need to adopt a finer resolution in the spanwise direction in order to capture the very anisotropic turbulent dynamics. Furthermore, it emerges the need of Direct Numerical Simulation (DNS) data in order to shed light on the compound role played by the turbulence model, the grid resolution and the inlet conditions.

A new fully coupled multiphase model for hygrothermal analysis and prediction of salt diffusion and crystallization in porous building materials is presented. The relative humidity, the temperature, the concentration of the dissolved salt and the concentration of precipitated salts are assumed as independent variables. A suitable modelling of the crystallization/dissolution and hydration/dehydration processes allows considering salts with hydrous and anhydrous crystals. Some numerical applications on fired-clay bricks show the effectiveness of the proposed approach.

The present work focuses on a posteriori , equilibrium based, reconstruction of transverse stress profiles in the finite element analysis of FSDT laminated plates. The accuracy of this reconstruction depends on accuracy of the first and second-order derivatives of the plate stress resultants, which is not guaranteed by most available low-order plate finite elements. To cure this trouble, two different strategies, based on the Recovery by Compatibility in Patches procedure, are here proposed and compared. Numerical results of typical reconstructed transverse stress profiles are presented showing the effectiveness of the proposed approach.

Losses from water distribution systems are reaching alarming levels in many cities throughout the world. Leakage is often the principal cause of water loss due to aging and deterioration of these systems and pressure has been verified to assume a key-role in water loss management. This paper presents a simple analytical model based on a beam with elastic constraints to estimate the leak area (from which the leakage is then estimated) in longitudinally cracked pressurized pipes and to evaluate the effect of pressure on the opening area of the crack. The model is calibrated on the results of a three-dimensional finite element analysis and then validated by experimental results. The validation has been carried out for a wide range of pipes made of different materials (PVC, cast iron, asbestos-cement, and steel) with radii ranging from 27.5 mm to 110 mm and thicknesses from 1.5 mm to 12 mm and crack lengths from 50 mm to 200 mm. The beam model, notwithstanding its simplicity, provides reliable leakage evaluations in longitudinally cracked pressurized pipes.

This paper presents a new numerical strategy for the design and verification of flexible falling rock barriers: passive protection measures for risk mitigation of potentially unstable rock slopes. The key point of the proposed approach is that notwithstanding the complexity of the simulated phenomenon, the resulting highly non-linear, dynamic model is simple and produces an accurate prediction of all the relevant parameters for barrier design, such as anchorage forces, net panel elongations and residual heights. The modelling procedure has been assessed using detailed experimental data obtained from a set of full-scale tests on three barrier prototypes with various energy absorption capacities (5000 kJ, 3000 kJ and 500 kJ). By comparison with the experimental results, the numerical model has shown to be reliable in capturing very accurately the barrier response to a block impact. Consequently, this method can be extended to investigate the behaviour of flexible falling rock protection barriers under conditions different from those encountered in full-scale tests. Therefore, the numerical procedure can be regarded as an effective tool used for designing and testing these structures.

This paper deals with a posteriori estimation of finite element error and adaptivity. In particular, an error estimator based on stress recovery by enforcing compatibility over local patches of elements is applied to guide adaptive analyses. Various numerical results of adaptive refinement are given, which show the efficiency and reliability of the proposed approach.

In this paper a new time discontinuous Galerkin (TDG) formulation for non-linear elastodynamics is presented. The new formulation embeds an energy correction which ensures truly energy decaying, thus allowing to achieve unconditional stability that, as shown in the paper, is not guaranteed by the classical TDG formulation. The resulting method is simple and easily implementable into existing finite element codes. Moreover, it inherits the desirable higher-order accuracy and high-frequency dissipation properties of the classical formulation. Numerical results illustrate the very good performance of the proposed formulation. Copyright © 2010 John Wiley & Sons, Ltd.

In this work, a simple solution strategy for the fully coupled problem of the diffusion of a mobile constituent into an elastic solid is proposed. The key features of the proposed solution strategy are a superconvergent strain recovery and a final stress filtering, suitably arranged with a standard recursive staggering scheme. The strategy is devised to overcome some shortcomings arising when solving the problem within the standard finite element framework and can be easily implemented by using existing finite element packages for uncoupled elasticity and diffusion problems. Numerical applications show the effectiveness of the proposed solution strategy.

In this paper, a mixed stress formulation for linear elastodynamic analysis based on a modified Hellinger–Reissner functional and a consistent approach for selecting finite element approximations are presented. The key idea in this new approach is to choose stress approximations by taking into account for suitable modes to equilibrate inertia forces. Feasibility and effectiveness of the proposed approach are numerically verified through three benchmark tests.

This paper compares two estimators for the dynamic identification of elastic constants of thick laminated composite plates. The plate’s response is modeled by finite elements based on Reddy’s third-order theory. The elastic constants are estimated within a Bayesian framework, using two estimators available in the literature. The estimators differ in the way they account for a priori information on the elastic constants to be identified. The resultant estimation procedures are critically examined and compared by paying special attention to the influence of a priori information on the final estimates. A unified interpretation of the two estimators is given and a modified strategy is proposed in order to improve reliability and convergence of the estimation process. Identification results for various case studies are presented.

International audience; A new patch based stress recovery procedure for elastoplastic analysis is presented in this paper. The formulation derives from the extension to the elastic-perfectly plastic case of the Recovery by Compatibility in Patches procedure recently proposed by the authors. The present procedure is designed to simultaneously reconstruct both a new stress field and a new plastic strain field, so to ensure that elastoplastic consistency is satisfied. The numerical results on two common benchmark problems show the effectiveness of the new procedure.