Wellbore instability, in particular in deep perforations, continues to be one of the major problem in the oil and gas industry, that can dramatically increase production costs. To prevent instabilities during perforation, wellbores are... more
Wellbore instability, in particular in deep perforations, continues to be one of the major problem in the oil and gas industry, that can dramatically increase production costs. To prevent instabilities during perforation, wellbores are temporarily supported by drilling mud pressure. If instability occurs, the value of the mud pressure needs to be sufficiently high to prevent compressional failure, but it should also be lower than a critical value that would cause tensile failure and unintentional hydraulic fracturing. Predicting faithfully the stress distribution around a borehole, and moreover the yielding and failure zones, is a challenging but fundamental task, essential to estimate the correct mud pressure and hence to prevent instabilities and sand production. This study focuses on quantifying the pressure distribution, stress field, plastic zones and the eventual inception of localized deformations around a horizontal borehole drilled at great depth through a highly porous roc...
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The paper aims to investigate the natural frequencies of sandwich plates by means of a Finite Element (FE) formulation based on the Reissner-Mindlin Zig-zag (RMZ) theory. The structures are made of a damaged isotropic soft-core and two... more
The paper aims to investigate the natural frequencies of sandwich plates by means of a Finite Element (FE) formulation based on the Reissner-Mindlin Zig-zag (RMZ) theory. The structures are made of a damaged isotropic soft-core and two external stiffer orthotropic face-sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. A non-uniform distribution of the reinforcing fibers is assumed along the thickness of the skin and is modeled analytically by means of peculiar expressions given as a function of the thickness coordinate. Several parametric analyses are carried out to investigate the mechanical behavior of these mul...
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PurposeThe purpose of this paper is to investigate the bond behaviour between fiber reinforced polymer (FRP) sheets and concrete elements, starting from available experimental evidences, through a calibrated and upgraded 3D... more
PurposeThe purpose of this paper is to investigate the bond behaviour between fiber reinforced polymer (FRP) sheets and concrete elements, starting from available experimental evidences, through a calibrated and upgraded 3D mathematical‐numerical model.Design/methodology/approachThe complex mechanism of debonding/peeling failure of FRP reinforcement is studied within the context of damage mechanics to appropriately catch transversal effects and developing a more realistic and comprehensive study of the delamination process. The FE ABAQUS© code has been supplemented with a numerical procedure accounting for Mazars's damage law inside the contact algorithm.FindingsIt has been shown that such an approach is able to catch the delamination evolution during loading processes as well.Originality/valueA Drucker‐Prager constitutive law is adopted for concrete whereas FRP elements are assumed to behave in a linear‐elastic manner, possibly undertaking large strains/displacements. Surface‐t...
Research Interests: Engineering, Mechanical Engineering, Civil Engineering, Materials Science, Structural Engineering, and 11 moreLinear Elasticity, Damage Mechanics, Reinforcement, Design Methodology, Fiber Reinforced Polymer, Numerical Model, Fibre Reinforced Plastic, Three Dimensional, Interdisciplinary Engineering, Engineering Computations, and Large Strain
ABSTRACT Guidelines for designing a concrete storage module and for its integration into a solar plant, respecting constraints linked both to an adequate solar field operation and to the production system based on ORC, are described. A... more
ABSTRACT Guidelines for designing a concrete storage module and for its integration into a solar plant, respecting constraints linked both to an adequate solar field operation and to the production system based on ORC, are described. A series of simplified procedures are developed to be used for a first module design and more sophisticated (even if more expensive) simulation techniques via the Finite Element Method are checked and upgraded. Once the ongoing experimental phase on a scaled storage prototype at the ENEA site of Casaccia has been concluded, the obtained data will be used for completing both the setup of the calculation instruments and the R&D activity dealing with the development of an appropriate concrete mixing, optimising its chemical–physical and durability performances, and with the module integration within a CSP system.
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Research Interests: Materials Science and CRC
Research Interests: Materials Science and CRC
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A numerical formulation is described in this paper to analyse fully three dimensional consolidation of deformable porous media, taking into account simultaneous fluid flows and thermal transport. The numerical procedure is implemented in... more
A numerical formulation is described in this paper to analyse fully three dimensional consolidation of deformable porous media, taking into account simultaneous fluid flows and thermal transport. The numerical procedure is implemented in a finite element code, which allows to investigate general three dimensional problems
The stress and strain states of composite concrete sections of bridge decks subjected to hygrometric variations are evaluated in this paper. As usual in this application field, prestressed concrete beams are considered, and after a given... more
The stress and strain states of composite concrete sections of bridge decks subjected to hygrometric variations are evaluated in this paper. As usual in this application field, prestressed concrete beams are considered, and after a given time concrete is cast to obtain the final composite section. In the analysis attention is focussed on the effects of the different ages of used concrete and the problems arising at the interface of the different constructive elements. A first approach to deal with this engineering solution with a specific computational tool is attempted for this purpose. Creep, shrinkage and damage effects are taken into account, within the framework of finite element method, using a suitable code which can be adapted for the simulation of structures of any shape.
Abstract The capability of modelling damage evolution in concrete materials represents a topic of relevance for improving the design of concrete structures and for the recovery of existing components. The present work aims to investigate... more
Abstract The capability of modelling damage evolution in concrete materials represents a topic of relevance for improving the design of concrete structures and for the recovery of existing components. The present work aims to investigate the collapsible behaviour of the Interfacial Transition Zone (ITZ) around coarse inclusions, by using a new cohesive contact law able to take into account the coupling between normal/peeling and shear stresses, specifically calibrated to take into account the roughness of various aggregate types. A series of numerical analyses have been carried out considering different material inclusions and distributions within concrete samples, so proving the capabilities of the proposed formulation.
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Abstract Two types of concretes were prepared in order to build thermal storage units for solar plants having as primary aim to improve thermal conductivity. The first type consists of concrete for casting on site (A), whereas the second... more
Abstract Two types of concretes were prepared in order to build thermal storage units for solar plants having as primary aim to improve thermal conductivity. The first type consists of concrete for casting on site (A), whereas the second for moulding upon vibration (B). Samples of both typologies were prepared changing type of additions or aggregates. The use of recycled materials into concrete (e.g. polyamide fibres from post-consumer textile carpet waste, metallic powders or shavings and steel fibres) was investigated. Fibre-reinforced concretes were tougher (up to 300%) than ordinary ones. All the concretes show high thermal conductivity and are good candidates for an efficient thermal storage unit, but the performances of type B concretes are better than those of type A. Moreover, the morphology of type B concretes appears compact and less cracked, even after thermal treatment at temperature higher than 300 °C. The thermal conductivity of the mix containing polyamide fibres and metallic shavings was 2.74 and 2.13 W/m °C, before and after a thermal treatment of 4 h at 300 °C, respectively.
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... Economic thermal storage is a technological key issue for the future success of solar thermal technologies. ... In saturated states (Figure 7), the thermodynamic properties of water can be taken into account in terms of specific... more
... Economic thermal storage is a technological key issue for the future success of solar thermal technologies. ... In saturated states (Figure 7), the thermodynamic properties of water can be taken into account in terms of specific volume of water, y, as a function of T ... Solar power plants ...
Research Interests: Engineering, Environmental Science, Heat Transfer, Low Cost Technology, New Technology, and 15 moreSolar Energy, Flow, Mathematical Sciences, Solar Power, Conceptual Design, Numerical, Design Methodology, High Temperature, High Performance Concrete, Fluid flow, Mathematical Model, Numerical Model, Concentrating Solar Power, Solar Power Plant, and Model simulation
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Finds the regions of dynamic instability of elastic beams constrained at the ends by means of translational and rotational elastic springs, using the equation of boundary frequencies. Obtains the diagrams showing the regions of... more
Finds the regions of dynamic instability of elastic beams constrained at the ends by means of translational and rotational elastic springs, using the equation of boundary frequencies. Obtains the diagrams showing the regions of instability of the beam, as a function of the dynamic component of the periodic forcing function and its frequency, from that equation in exact form. In this procedure inertial, stiffness and constraint characteristics of the examined system are taken into account. Presents selected applications concerning the analysed problem.
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In this paper the finite element method is used to find the regions of dynamic stability of beams and frames. A suitable numerical procedure allows diagrams to be obtained where these regions are located as functions of the dynamic force... more
In this paper the finite element method is used to find the regions of dynamic stability of beams and frames. A suitable numerical procedure allows diagrams to be obtained where these regions are located as functions of the dynamic force applied and vibration frequency of the ...
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ABSTRACT Temperatures and stress transients due to hydration process in concrete casting for dam constructions and to thermal exchanges between concrete and its surrounding environment are analysed. The problem under investigation is... more
ABSTRACT Temperatures and stress transients due to hydration process in concrete casting for dam constructions and to thermal exchanges between concrete and its surrounding environment are analysed. The problem under investigation is highly nonlinear due to different reasons. Placing technique of concrete is carried out by means of large block castings which are superimposed at different times. Concrete surfaces may be cooled using water at ambient temperature or at a lesser temperature; thermal exchanges between concrete and external ambient are affected by the increasing extension of casting surface, by solar radiation and wind action. Thermal stresses due to the temperature transients are produced and cracks may appear in massive concrete.The numerical analysis of corresponding complex phenomena is carried out according to the following lines. Temperature field is calculated at each time step taking into account the above mentioned nonlinearities, then for each time step equilibrium is imposed for finding displacements and stresses using maturity dependent constitutive relationships. Time integration of the nonlinear equation of heat transport is carried out using a two-level scheme with variable step sizes. Thermal and mechanical fields are then found for the whole time transient.