Influence of corrosive phenomena on bearing capacity of RC and PC beams

Malerba, Pier Giorgio,Sgambi, Luca,Ielmini, Diego,Gotti, Giordano Techno-Press 2017 Advances in concrete construction Vol.5 No.2

The attack of environmental aggressive agents progressively reduces the structural reliability of buildings and infrastructures and, in the worst exposition conditions, may even lead to their collapse in the long period. A change in the material and sectional characteristics of a structural element, due to the environmental damaging effects, changes its mechanical behaviour and varies both the internal stress redistribution and the kinematics through which it reaches its ultimate state. To identify such a behaviour, the evolution of both the damaging process and its mechanical consequences have to be taken into account. This paper presents a computational approach for the analysis of reinforced and prestressed concrete elements under sustained loading conditions and subjected to given damaging scenarios. The effects of the diffusion of aggressive agents, of the onset and development of the corrosion state in the reinforcement and the corresponding mechanical response are studied. As known, the corrosion on the reinforcing bars influences the damaging rate in the cracking pattern evolution; hence, the damage development and the mechanical behaviours are considered as coupled phenomena. The reliability of such an approach is validated in modelling the diffusion of the aggressive agents and the changes in the mechanical response of simple structural elements whose experimental behaviour is reported in Literature. A second set of analyses studies the effects of the corrosion of the tendons of a P.C. beam and explores potentially unexpected structural responses caused by corrosion under different aggressive exposition. The role of the different types and of the different positions of the damaging agents is discussed. In particular, it is shown how the collapse mode of the beam may switch from flexural to shear type, in case corrosion is caused by a localized chloride attack in the shear span.

An Extended Force Density Method for the form finding of cable systems with new forms

Malerba, P.G.,Patelli, M.,Quagliaroli, M. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.2

The Force Density Method (FDM) is a well known and extremely versatile tool in form finding of cable nets. In its linear formulation such method makes it possible to find all the possible equilibrium configurations of a net of cables having a certain given connectivity and given boundary conditions on the nodes. Each singular configuration corresponds to an assumed force density distribution. Its improvement as Non-Linear Force Density Method (NLFDM) introduces the possibility of imposing assigned relative distances among the nodes, the tensile level in the elements and/or their initial undeformed length. In this paper an Extended Force Density Method (EFDM) is proposed, which makes it possible to set conditions in terms of given fixed nodal reactions or, in other words, to fix the positions of a certain number of nodes and, at the same time, to impose the intensity of the reaction force. Through such extension, the (EFDM) enables us to deal with form findings problems of cable nets subjected to given constraints and, in particular, with mixed structures, made of cables and struts. The efficiency and the robustness of method are assessed through comparisons with other form finding techniques in dealing with characteristic applications to the prestress design of cable systems. As a further extension, the EFDM is applied to structures having some parts not yet geometrically defined, as can happen in designing new creative forms.

An Extended Force Density Method for the form finding of cable systems with new forms

P.G. Malerba,Politecnico di Milano,M. Quagliaroli 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.2

The Force Density Method (FDM) is a well known and extremely versatile tool in form finding of cable nets. In its linear formulation such method makes it possible to find all the possible equilibrium configurations of a net of cables having a certain given connectivity and given boundary conditions on the nodes. Each singular configuration corresponds to an assumed force density distribution. Its improvement as Non-Linear Force Density Method (NLFDM) introduces the possibility of imposing assigned relative distances among the nodes, the tensile level in the elements and/or their initial undeformed length. In this paper an Extended Force Density Method (EFDM) is proposed, which makes it possible to set conditions in terms of given fixed nodal reactions or, in other words, to fix the positions of a certain number of nodes and, at the same time, to impose the intensity of the reaction force. Through such extension, the (EFDM) enables us to deal with form findings problems of cable nets subjected to given constraints and, in particular, with mixed structures, made of cables and struts. The efficiency and the robustness of method are assessed through comparisons with other form finding techniques in dealing with characteristic applications to the prestress design of cable systems. As a further extension, the EFDM is applied to structures having some parts not yet geometrically defined, as can happen in designing new creative forms.

The role of softening in the numerical analysis of R.C. framed structures

Bontempi, Franco,Malerba, Pier Giorgio Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.6

Reinforced Concrete beams with tension and compression softening material constitutive laws are studied. Energy-based and non-local regularisation techniques are presented and applied to a R.C. element. The element characteristics (sectional tangent stiffness matrix, element tangent stiffness matrix restoring forces) are directly derived from their symbolic expressions through numerical integration. In this way the same spatial grid allows us to obtain a non-local strain estimate and also to sample the contributions to the element stiffness matrix. Three examples show the spurious behaviors due to the strain localization and the stabilization effects given by the regularisation techniques, both in the case of tension and compression softening. The possibility to overestimate the ultimate load level when the non-local strain measure is applied to a non softening material is shown.

Catch-up cycles and changes in industrial leadership:Windows of opportunity and responses of firms and countries in the evolution of sectoral systems

Lee, K.,Malerba, F. Elsevier Science Publishers B.V. (North-Holland) 2017 RESEARCH POLICY Vol.46 No.2

This study proposes a framework that aims to explain why successive changes in industry leadership (called also the catch-up cycle) occur over time in a sector. In catch-up cycles, latecomer firms and countries emerge as international leaders, whereas incumbents lose their previous positions. New leaders are then dethroned by newcomers. To identify factors at the base of catch-up cycles, this article adopts a sectoral system framework and identifies windows of opportunity that may emerge during the long-run evolution of an industry. This study proposes three windows related to the specific dimensions of a sectoral system. One dimension is related to changes in knowledge and technology. The second dimension pertains to changes in demand, and the third includes changes in institutions and public policy. The combination of the opening of a window (technological, demand, or institutional/policy) and the responses of firms and other components of the sectoral system of the latecomer and incumbent countries determines changes in industrial leadership and catch-up. Sectors differ according to the type of windows that may open and the responses of firms and other components of systems. Empirical evidence of catch-up cycles is presented from six sectors, namely mobile phones, cameras, semiconductors, steel, mid-sized jets, and wines.

Stress path adapting Strut-and-Tie models in cracked and uncracked R.C. elements

Biondini, Fabio,Bontempi, Franco,Malerba, Pier Giorgio Techno-Press 2001 Structural Engineering and Mechanics, An Int'l Jou Vol.12 No.6

In this paper, a general method for the automatic search for Strut-and-Tie (S&T) models representative of possible resistant mechanisms in reinforced concrete elements is proposed. The representativeness criterion here adopted is inspired to the principle of minimum strain energy and requires the consistency of the model with a reference stress field. In particular, a highly indeterminate pin-jointed framework of a given layout is generated within the assigned geometry of the concrete element and an optimum truss is found by the minimisation of a suitable objective function. Such a function allows us to search the optimum truss according to a reference stress field deduced through a F.E.A. and assumed as representative of the given continuum. The theoretical principles and the mathematical formulation of the method are firstly explained; the search for a S&T model suitable for the design of a deep beam shows the method capability in handling the reference stress path. Finally, since the analysis may consider the structure as linear-elastic or cracked and non-linear in both the component materials, it is shown how the proposed procedure allows us to verify the possibilities of activation of the design model, oriented to the serviceability condition and deduced in the linear elastic field, by following the evolution of the resistant mechanisms in the cracked non-linear field up to the structural failure.

Toward a theory of catch-up cycles

Keun Lee,Franco Malerba 한국경영학회 2014 한국경영학회 통합학술발표논문집 Vol.2014 No.8

Functional Rescue of Dystrophin Deficiency in Mice Caused by Frameshift Mutations Using <i>Campylobacter jejuni</i> Cas9

Koo, Taeyoung,Lu-Nguyen, Ngoc B.,Malerba, Alberto,Kim, Eunji,Kim, Daesik,Cappellari, Ornella,Cho, Hee-Yeon,Dickson, George,Popplewell, Linda,Kim, Jin-Soo American Society of GeneCell Therapy 2018 Molecular therapy Vol.26 No.6

<▼1><P>Duchenne muscular dystrophy (DMD) is a fatal, X-linked muscle-wasting disease caused by mutations in the <I>DMD</I> gene. In 51% of DMD cases, a reading frame is disrupted because of deletion of several exons. Here, we show that CjCas9 derived from <I>Campylobacter jejuni</I> can be used as a gene-editing tool to correct an out-of-frame <I>Dmd</I> exon in <I>Dmd</I> knockout mice. Herein, we used Cas9 derived from <I>S. pyogenes</I> to generate <I>Dmd</I> knockout mice with a frameshift mutation in <I>Dmd</I> gene. Then, we expressed CjCas9, its single-guide RNA, and the EGFP gene in the <I>tibialis anterior</I> muscle of the <I>Dmd</I> knockout mice using an all-in-one adeno-associated virus (AAV) vector. CjCas9 cleaved the target site in the <I>Dmd</I> gene efficiently <I>in vivo</I> and induced small insertions or deletions at the target site. This treatment resulted in conversion of the disrupted <I>Dmd</I> reading frame from out of frame to in frame, leading to the expression of dystrophin in the sarcolemma. Importantly, muscle strength was enhanced in the CjCas9-treated muscles, without off-target mutations, indicating high efficiency and specificity of CjCas9. This work suggests that <I>in vivo DMD</I> frame correction, mediated by CjCas9, has great potential for the treatment of DMD and other neuromuscular diseases.</P></▼1><▼2><P>Koo et al. demonstrate that CjCas9 derived from <I>Campylobacter jejuni</I> can be used as a gene-editing tool to correct an out-of-frame <I>Dmd</I> exon in <I>Dmd</I> knockout mice. This study provides the therapeutic utility of CjCas9 for the treatment of Duchenne muscular dystrophy and other neuromuscular diseases.</P></▼2>

Next generation sequencing: new tools in immunology and hematology

Antonio Mori,Sara Deola,Luciano Xumerle,Vladan Mijatovic,Giovanni Malerba,Vladia Monsurrò 대한혈액학회 2013 Blood Research Vol.48 No.4

One of the hallmarks of the adaptive immune system is the specificity of B and T cell receptors. Thanks to somatic recombination, a large repertoire of receptors can be gen-erated within an individual that guarantee the recognition of a vast number of antigens. Monoclonal antibodies have limited applicability, given the high degree of diversity among these receptors, in BCR and TCR monitoring. Furthermore, with regard to cancer, better characterization of complex genomes and the ability to monitor tumor-specific cryptic mutations or translocations are needed to develop better tailored therapies. Novel technologies, by enhancing the ability of BCR and TCR monitoring, can help in the search for minimal residual disease during hematological malignancy diagnosis and follow-up, and can aid in improving bone marrow transplantation techniques. Recently, a novel tech-nology known as next generation sequencing has been developed; this allows the recog-nition of unique sequences and provides depth of coverage, heterogeneity, and accuracy of sequencing. This provides a powerful tool that, along with microarray analysis for gene expression, may become integral in resolving the remaining key problems in hematology. This review describes the state of the art of this novel technology, its application in the immunological and hematological fields, and the possible benefits it will provide for the hematology and immunology community.