1,721,026 research outputs found
Assemblaggi strutturali mediante incollaggio. Modellazione ed analisi del comportamento di interfaccia
No full textNegli ultimi due decenni la richiesta di strutture sempre più
efficienti e a ridotto impatto ambientale ha promosso significativamente
l’impiego dei compositi nell’Ingegneria Civile. Le
diverse realizzazioni consentono di trarre utili indicazioni sugli
aspetti da sviluppare al fine di un loro efficace utilizzo, primi
tra i quali emergono la necessità di implementare una raffinata
modellazione meccanica ed adeguati criteri di progettazione
strutturale, obiettivi raggiungibili solo a patto di garantire
la necessaria continuità tra la ricerca di base ed applicata,
lo sviluppo di metodologie di calcolo e criteri progettuali
e l’elaborazione di raccomandazioni tecniche e codici
normativi dedicat
Theoretical Aspects and Computational Issues in Plasticity and Viscoplasticity
No full textIn the present dissertation small deformation problems for elastoviscoplastic
materials are addressed, with special emphasis on the computational aspects.
Accordingly, in the presentation of the constitutive theories which will be dealt
with throughout this work, the discussion will be con ned to the mathematical
aspects of the theory which are relevant to the numerical solution of the nonlinear
boundary value problem arising in elasto- and elasto/visco- plasticity and to the
analysis of the related computational strategies
Graded damage solutions in one dimension
Full text linkA regularized damage model is considered named "Graded damage" in which the gradient enhancement has the form of an explicit bound for the spatial gradient of damage. The key features of the proposed approach are demonstrated by computing the analytical solution of two problems that are one-parameter dependent. The first one is the classical one-dimensional damageable rod under tensile load, for which the hardening function is determined based on the equivalence with a given cohesive relationship. The second application is a mode-I delamination problem for which the cohesive law for the interface is formulated starting from the graded damage concept, i.e. by prescribing the shape
of damage distribution within the cohesive process zone
Giunti e connessioni adesive. Una sfida per la moderna industria della costruzione
No full textI significativi progressi maturati nella sintesi e nello sviluppo
di adesivi strutturali lasciano intravedere l’enorme potenziale
dei giunti adesivi nelle applicazioni ingegneristiche, soprattutto
per la realizzazione di efficaci connessioni tra elementi
strutturali in materiali dissimil
Limit state analysis of RC structures
Full text linkThe inelastic static pushover analysis has become a popular tool for evaluating the seismic capacity of structures. It is able of predicting the seismic force and deformation demands by accounting in an approximate manner for the inelastic redistribution of internal forces. Though approximate in nature and based on static loading, if properly used the pushover analysis can provide many significant insights into the structural behaviour and also put forward the design weaknesses that may be hidden in the elastic analysis. The main features of the conventional pushover analysis are well described in [1], where are also emphasized limitations and possible causes that may produce loss of accuracy of the method. A basic prerequisite for successful applications of the method is an adequate knowledge of the inelastic behaviour of structural elements. This is particularly true for those structures containing shear walls that, if not properly described, may render the results of the analysis completely meaningless.
In this work we show how, under appropriate hypotheses, one can introduce steel reinforcement into shear walls by appealing to a semi-analytical multi-scale approach. In particular, reinforcements are taken into account using an embedded beam approach, the usual conventional material behaviour, i.e. the the so-called parabolic-rectangular stress block for concrete and ideal elastic-plastic for steel as of Eurocode 2, and a fiber-free integration, that provides the exact solution for stress resultants over the cross section of the beam itself.
Representative numerical simulations are shown that illustrate the capabilities of the proposed approach, that allows one to carry out accurate nonlinear analyses of full-scale reinforced concrete structures with relatively reduced computational effort
Characterization of a cohesive-zone model describing damage and de-cohesion at bonded interfaces. Sensitivity analysis and mode-I parameter identification
No full textThe identification of mode-I parameters of a cohesive-zone model for the analysis of adhesive joints is
presented. It is based on an experimental–numerical methodology whereby the optimal parameters
are obtained as the solution of a nonlinear programming problem. The data set for inverse analysis is provided
either by local kinematic data, by global static data, or a combination of the two. Parameter sensitivities
are computed via direct differentiation and identification exercises are discussed that show the
effectiveness of the procedure and its stability with respect to noise and time–space sampling
Consistent derivation of the constitutive algorithm for plane stress isotropic plasticity. Part II: Computational issues
No full textThe implementation of the projected algorithm and of the consistent tangent tensor for general isotropic three-invariant elastoplastic models under plane stress conditions discussed in Part I of this paper [Valoroso, N., Rosati, L., 2008. Consistent derivation of the constitutive algorithm for plane stress isotropic plasticity. Part I: Theoretical formulation. International Journal of Solids and Structures, doi: 10.1016/j.ijsolstr.2008.08.012.] is addressed. The connections between the general three-dimensional case and the plane stress problem are analyzed in detail and an algorithmic treatment taking full advantage of the isotropic properties of the model is presented. In particular, intrinsic (matrix-free) expressions are provided for all steps of the stress computation scheme that allow one to carry out the numerical implementation in a way that is completely independent from the matrix representations. The numerical performances of the present solution scheme are evaluated through representative numerical examples
Evaluation of conjugate stresses to Seth’s strain tensors
No full textAn explicit expression providing the symmetric stress tensor T(m) conjugate to the Seth’s strain measure
E(m) for each integer m 6= 0 is presented. The result is obtained by exploiting an original approach
for the solution of a tensor equation in the unknown T(m) expressed as function of the powers of
the right stretch tensor U. The proposed approach is based upon the spectral decomposition of U
and exploits some peculiar features of the set of fourth-order tensors obtained as linear combination
of dyadic and square tensor products of the eigenprojectors of U. On the basis of such properties it
is shown that the unknown T(m) can be expressed in the given reference frame as linear combination
of six fourth-order tensors scaled through coefficients which are rational functions of the eigenvalues of U
Una metodologia inversa basata su misure cinematiche a scale diverse, per la calibrazione di modelli di interfaccia
No full textIn questa comunicazione si propone una metodologia inversa per la caratterizzazione
meccanica di modelli d’interfaccia, basata su misure di campo cinematiche, a scale diverse.
Si fa riferimento sia a prove in modo I in configurazione simmetrica Double Cantilever Beam
(DCB) su giunto adesivo, sia ad una prova di frattura in modo misto su un assemblato con rinforzo
a Z per applicazioni aerospaziali. Alla macroscala, le immagini digitali permettono di inquadrare
quasi l’intero provino, con una dimensione del pixel di circa 20 micron. Alla scala microscopica, sul
lato opposto del provino, viene monitorata con speciali obiettivi una regione di pochi millimetri di
lato, con al centro il giunto adesivo, con una risoluzione di circa 2 micron
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