A discrete model for layered growth

In this work we present a discrete model that captures the fundamental properties of additively manufactured solids in a minimal setting. The model is based on simplified kinematics and allows for the onset of incompatible deformations between discrete layers of an additively manufactured stack. Thanks to the discrete nature of the model, we obtain an averaged formulation of mechanical equilibrium for the growing stack, leading to closed-form solutions that are both analytically simple and physically transparent. In particular, we are able to explain the origin of residual stresses by the accumulation of incompatible deformations between adjacent layers. At the same time, we are able to formulate the technologically relevant inverse problem that provides the deposition protocol required to produce a desired state of internal stress in the manufactured stack. Another important aspect analyzed in the work is the role played by an ideal ``glue'' between the layers, whose presence is fundamental to prevent their sliding and whose mechanical behavior can quantitatively influence the final stress distribution in the stack. Although the model is an elementary approximation of additive manufacturing, its simplicity makes it possible to highlight how the controls exerted during deposition will have qualitative or quantitative effects on the final stress state of the stack. This understanding is crucial in shedding light on the complex mechanical behavior of additive manufactured solids.Comment: 25 pages, 10 figure

Numerical simulation of the de-bonding phenomenon of FRCM strengthening systems

Aim of the paper is to present a one dimensional simple model for the study of the bond behavior of Fabric Reinforced Cementitious Matrix (FRCM) strengthening systems externally applied to structural substrates. The equilibrium of an infinitesimal portion of the reinforcement and the mortar layers composing the strengthening systems allows to derive the governing equations. An analytical solution is determined solving the system of differential equations. In particular, in the first part of the paper a nonlinear shear-stress slip law characterized by a brittle post-peak behavior with a residual shear strength in the post peak phase is introduced for either the lower reinforcement-mortar interface (approach 1) or both the lower and the upper interface (approach 2). In the latter approach, a calibration of the shear strength of the upper interface is proposed in order to implicitly account for the effect of the damage of the mortar on the bond behavior. In the second part of the paper it is presented the solution of the problem in the case of softening behavior by approximating the shear-stress slip law throughout a step function. Comparisons with experimental data, available in literature, are presented in order to assess the reliability of the proposed approach

Numerical simulation of the de-bonding phenomenon of FRCM strengthening systems

Aim of the paper is to present a one dimensional simple model for the study of the bond behavior of Fabric Reinforced Cementitious Matrix (FRCM) strengthening systems externally applied to structural substrates. The equilibrium of an infinitesimal portion of the reinforcement and the mortar layers composing the strengthening systems allows to derive the governing equations. An analytical solution is determined solving the system of differential equations. In particular, in the first part of the paper a nonlinear shear-stress slip law characterized by a brittle post-peak behavior with a residual shear strength in the post peak phase is introduced for either the lower reinforcement-mortar interface (approach 1) or both the lower and the upper interface (approach 2). In the latter approach, a calibration of the shear strength of the upper interface is proposed in order to implicitly account for the effect of the damage of the mortar on the bond behavior. In the second part of the paper it is presented the solution of the problem in the case of softening behavior by approximating the shear-stress slip law throughout a step function. Comparisons with experimental data, available in literature, are presented in order to assess the reliability of the proposed approach

analysis of reinforced concrete slabs under blast loading

Abstract Aim of the present paper is the study of the blast effects on reinforced concrete slabs used for civil buildings. Reinforced concrete slab samples with and without partitions subjected to explosions are numerically analyzed adopting the explicit finite element code LS-DYNA. In particular, the explosive is considered in direct contact with the sample surface. Each material composing the slab is modeled adopting a suitable non linear constitutive model. The partitions are modelled as rigid bodies and they are placed in two different positions. Numerical analyses are performed on the slabs with and without partitions, considering the same amount of explosive, in order to determine the influence of partitions on the blast resistance of the slabs. Comparisons in terms of the damage produced in the slab are carried out

Therapeutic choices and disease activity after 2 years of treatment with cladribine: An Italian multicenter study (CladStop)

background and purpose: cladribine tablets, a purine analogue antimetabolite, offer a unique treatment regimen, involving short courses at the start of the first and second year, with no further treatment needed in years 3 and 4. However, comprehensive evidence regarding patient outcomes beyond the initial 24 months of cladribine treatment is limited. methods: this retrospective, multicenter study enrolled 204 patients with multiple sclerosis who had completed the 2-year course of cladribine treatment. the primary outcomes were therapeutic choices and clinical disease activity assessed by annualized relapse rate after the 2-year treatment course. results: a total of 204 patients were enrolled; most patients (75.4%) did not initiate new treatments in the 12 months postcladribine. the study found a significant reduction in annualized relapse rate at the 12-month follow-up after cladribine completion compared to the year prior to starting therapy (0.07 +/- 0.25 vs. 0.82 +/- 0.80, p < 0.001). furthermore, patients with relapses during cladribine treatment were more likely to start new therapies, whereas older patients were less likely. the safety profile of cladribine was favorable, with lymphopenia being the primary registered adverse event. conclusions: this study provides insights into therapeutic choices and disease activity following cladribine treatment. It highlights cladribine's effectiveness in reducing relapse rates and disability progression, reaffirming its favorable safety profile. real-world data, aligned with previous reports, draw attention to ocrelizumab and natalizumab as common choices after cladribine. however, larger, prospective studies for validation and a more comprehensive understanding of cladribine's long-term impact are necessary

Modellazione del calcestruzzo fibrorinforzato

Dottorato di ricerca in ingegneria delle strutture. 12. ciclo. Coordinatore Franco Maceri. Tutori Antonio Grimaldi e Elio SaccoConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal