Open-source digital technologies for low-cost monitoring of historical constructions

This paper shows new possibilities of using novel, open-source, low-cost platforms for the structural health monitoring of heritage structures. The objective of the study is to present an assessment of increasingly available open-source digital modeling and fabrication technologies in order to identify the suitable counterparts of the typical components of a continuous static monitoring system for a historical construction. The results of the research include a simple case-study, which is presented with low-cost, open-source, calibrated components, as well as an assessment of different alternatives for deploying basic structural health monitoring arrangements. The results of the research show the great potential of these existing technologies that may help to promote a widespread and cost-efficient monitoring of the built cultural heritage. Such scenario may contribute to the onset of commonplace digital records of historical constructions in an open-source, versatile and reliable fashion.Peer ReviewedPostprint (author's final draft

Enantioselective Approaches and Domino Sequences for the Synthesis of Compounds of Biological Interest

Neuropeptide S (NPS) is the endogenous ligand of the previously orphan G-protein coupled receptor, recently named NPSR.12 NPS is a small peptide of 20 amino acids and rapresents the endogenous ligand of NPSR. In cells expressing the recombinant NPSR receptor, NPS selectively binds and activates its receptor, producing intracellular calcium mobilization and an increase of cAMP levels. The NPS-NPSR receptor system regulates important biological functions such as sleep/waking, locomotion, anxiety and food intake. (R/S) SHA-68 21 is the first non-peptide antagonist of NPSR receptor; actually only a class of molecules able to interact with NPSR are reported in the literature and they are the same oxazol-piperazine structure. Initially, in order to confirm the published data, we decided to synthesize SHA 68 in racemic form following the Okamura’s methodology21. The high selectivity of (R/S)-SHA 68 for NPSR and its good antagonist activity prompted us to synthesize the enantiomers of this non-peptide compound, starting from cheap commercially available reagents as chiral auxiliary. In order to define the conformation of the piperazine ring in this two enantiomers we performed a series of NMR experiments leading to define a chair conformation where the substituent in C9 was placed in equatorial position. To know the absolute configuration of the new chiral centre X ray analysis was performed on suitable crystals that show us the R configuration of the new stereogenic centre. From a pharmacological point of view (R)-SHA 68 was demonstrated to be the antagonist of the receptor of the Neuropeptide S. This new class of non-peptide NPSR antagonists provides additional tools for in vitro and in vivo studies required to elucidate the NPSR conformation, adding new informations to well know NPS-NPSR system. In the frame of the synthesis of biological active chiral compounds I have spend nine months at the Pierre et Marie Curie University in Paris under the supervision of Professor Giovanni Poli, focusing the attention on the synthesis of natural product (-)- Steganacin. This stage allowed me to view a different approach for the selective generation of new structures using a palladium catalysed domino reactions instead of the use of chiral auxiliaries used for the synthesis of (R) and (S)-SHA 68. Steganacin was isolated from a plant of South Africa, Steganotaenia araliacea.31 The interest of chemists for the (-)-Steganacin was initially motivated by its antitumor activity; 34 it is for this reason that in literature we found different total syntheses of this molecule. From a structural point of view the (-)-Steganacine presents a γ-lactonic skeleton condensed to an eight membered ring, a biarylic portion and three contiguous stereogenic centers with a relative stereochemistry trans, trans. Aim of this project is the synthesis of an aza-analogue of Steganacine in which the lactone structure is replaced by a γ-lactam moiety. The synthetic process starts from a commercially available propargyl alcohol to afford in seven steps the desired cyclization precursor in 19 % yield. The key step of our project was previously studied in the laboratories of Prof. Giovanni Poli and reported in literature by Kammerer et al. in 2009.41 This is an original regioand stereoselective synthesis of aryl substituted pyrrolidones by a phosphine-free Pdcatalyzed allene carbopalladation/allylic alkylation sequence. This reaction allowed us to obtain the key intermediate in 74% yield. After benzylation of this key intermediate, several strategies to remove the methoxycarbonyl group were tested, the best solution being hydrolysis in ethylene glycol at high temperatures. The next study will focus on the non-phenolic oxidative coupling between the two aromatic moieties to formed an eight membered ring. Then, an oxidative cleavage of the double bond followed by a diastereoselective reduction of the resulting ketone and final alcohol acetylation should afford the desired (-)-Steganacin aza-analogue

CONTINUUM DAMAGE MODEL FOR NONLINEAR ANALYSIS OF MASONRY STRUCTURES

The present work focuses on the formulation of a Continuum Damage Mechanics model for nonlinear analysis of masonry structural elements. The material is studied at the macro-level, i.e. it is modelled as a homogeneous orthotropic continuum. The orthotropic behaviour is simulated by means of an original methodology, which is based on nonlinear damage constitutive laws and on the concept of mapped tensors from the anisotropic real space to the isotropic fictitious one. It is based on establishing a one-to-one mapping relationship between the behaviour of an anisotropic real material and that of an isotropic fictitious one. Therefore, the problem is solved in the isotropic fictitious space and the results are transported to the real field. The application of this idea to strain-based Continuum Damage Models is rather innovative. The proposed theory is a generalization of classical theories and allows us to use the models and algorithms developed for isotropic materials. A first version of the model makes use of an isotropic scalar damage model. The adoption of such a simple constitutive model in the fictitious space, together with an appropriate definition of the mathematical transformation between the two spaces, provides a damage model for orthotropic materials able to reproduce the overall nonlinear behaviour, including stiffness degradation and strain-hardening/softening response. The relationship between the two spaces is expressed in terms of a transformation tensor which contains all the information concerning the real orthotropy of the material. A major advantage of this working strategy lies in the possibility of adjusting an arbitrary isotropic criterion to the particular behaviour of the orthotropic material. Moreover, orthotropic elastic and inelastic behaviours can be modelled in such a way that totally different mechanical responses can be predicted along the material axes. The aforementioned approach is then refined in order to account for different behaviours of masonry in tension and compression. The aim of studying a real material via an equivalent fictitious solid is achieved by means of the appropriate definitions of two transformation tensors related to tensile or compressive states, respectively. These important assumptions permit to consider two individual damage criteria, according to different failure mechanisms, i.e. cracking and crushing. The constitutive model adopted in the fictitious space makes use of two scalar variables, which monitor the local damage under tension and compression, respectively. Such a model, which is based on a stress tensor split into tensile and compressive contributions that allows the model to contemplate orthotropic induced damage, permits also to account for masonry unilateral effects. The orthotropic nature of the Tension-Compression Damage Model adopted in the fictitious space is demonstrated. This feature, both with the assumption of two distinct damage criteria for tension and compression, does not permit to term the fictitious space as “isotropic”. Therefore, the proposed formulation turns the original concept of “mapping the real space into an isotropic fictitious one” into the innovative and more general one of “mapping the real space into a favourable (or convenient) fictitious one”. Validation of the model is carried out by means of comparisons with experimental results on different types of orthotropic masonry. The model is fully formulated for the 2-dimensional case. However, it can be easily extended to the 3-dimensional case. It provides high algorithmic efficiency, a feature of primary importance when analyses of even large scale masonry structures are carried out. To account for this requisite it adopts a strain-driven formalism consistent with standard displacement-based finite element codes. The implementation in finite element programs is straightforward. Finally, a localized damage model for orthotropic materials is formulated. This is achieved by means of the implementation of a crack tracking algorithm, which forces the crack to develop along a single row of finite elements. Compared with the smeared cracking approach, such an approach shows a better capacity to predict realistic collapsing mechanisms. The resulting damage in the ultimate condition appears localized in individual cracks. Moreover, the results do not suffer from spurious mesh-size or mesh-bias dependence. The numerical tool is finally validated via a finite element analysis of an in-plane loaded masonry shear wall

Dynamic identification and static loading tests of timbrel vaults: application to a Modernist 20th century heritage structure

This is an Accepted Manuscript of an article published by Taylor & Francis Group in International Journal of Architectural Heritage on 2017, available online at: http://www.tandfonline.com/10.1080/15583058.2016.1277566This paper presents the study of the structural performance of a set of timbrel vaults belonging to the so-called Administration Pavilion of the Hospital de Sant Pau, a large-scale hospital complex located in Barcelona. The paper includes three parts. First, the Administration pavilion of Hospital de Sant Pau is described by putting the emphasis on the geometry of the masonry vaults and the combined utilisation of steel and masonry structural members. Second, laboratory and in-situ experiments are discussed. Finally, the behaviour observed during the dynamic-identification and the static-loading tests is simulated by means of FEM analysis. The FEM models prepared to analyse the vaults take explicitly into account the direct effect of secondary masonry structural elements, such as the upper slab and the extrados stiffening diaphragms. The comparison indicates that the consideration of these structural elements is essential for an adequate FEM simulation of both the dynamic and the static behaviour of the timbrel vaults.Peer ReviewedPostprint (author's final draft

Experimental characterization of mortar by testing on small specimens

The experimental characterization of mortar mechanical properties in existing masonry constructions is considerably complex. Whereas bricks parameters can be assessed with a sufficient precision, the mortar properties are very difficult to obtain and the results are highly dispersed. For instance, the in-situ techniques based on the measurement of the amount of energy required to drill a small cavity provide very scattered values that should be handled cautiously. Also, the characterization of existing mortar joints by means of surface testing may be difficult, since the surface decay or even the presence of new restoration mortar may spoil the results. On the other hand, tests on small mortar cubes or double punch tests usually lead to inaccurate estimates of mechanical characteristics, since the confining effect exercised by bricks on the mortar layer is completely disregarded. Another difficulty is the extraction of undisturbed specimens from the joints of existing brickwork. Such problems can be overcome by laboratory destructive testing on small specimens including both bricks and mortar. This activity is suitable for existing historic buildings, since it does not inflict severe damage on the structural element. This work presents the results of a comprehensive experimental program on cores including a central mortar layer along a symmetry plane. Such specimens were easily extracted by different panels of an existing historical building using a common core drill. The cores were subjected to splitting test with a particular set-up, providing 30°, 45° or 60° inclinations of the mortar layer with respect to the loading plane. This test induces a mixed compression–shear stress state in the central mortar layer. The experimental results have been interpreted using different failure criteria in order to assess the mechanical properties of mortar.Postprint (published version

Tracking multi-directional intersecting cracks in numerical modelling of masonry shear walls under cyclic loading

In-plane cyclic loading of masonry walls induces a complex failure pattern composed of multiple diagonal shear cracks, as well as flexural cracks. The realistic modelling of such induced localized cracking necessitates the use of costly direct numerical simulations with detailed information on both the properties and geometry of masonry components. On the contrary, computationally efficient macro-models using standard smeared-crack approaches often result in a poor representation of fracture in the simulated material, not properly localized and biased by the finite element mesh orientation. This work proposes a possible remedy to these drawbacks of macro-models through the use of a crack-tracking algorithm. The macro-modelling approach results in an affordable computational cost, while the tracking algorithm aids the mesh-bias independent and localized representation of cracking. A novel methodology is presented that allows the simulation of intersecting and multi-directional cracks using tracking algorithms. This development extends the use of localized crack approaches using tracking algorithms to a wider field of applications exhibiting multiple, arbitrary and interacting cracking. The paper presents also a novel formulation including into an orthotropic damage model the description of irreversible deformations under shear loading. The proposed approach is calibrated through the comparison with an experimental test on a masonry shear wall against in-plane cyclic loading

Multiscale computational first order homogenization of thick shells for the analysis of out-of-plane loaded masonry walls

This work presents a multiscale method based on computational homogenization for the analysis of general heterogeneous thick shell structures, with special focus on periodic brick-masonry walls. The proposed method is designed for the analysis of shells whose micro-structure is heterogeneous in the in-plane directions, but initially homogeneous in the shell-thickness direction, a structural topology that can be found in single-leaf brick masonry walls. Under this assumption, this work proposes an efficient homogenization scheme where both the macro-scale and the micro-scale are described by the same shell theory. The proposed method is then applied to the analysis of out-of-plane loaded brick-masonry walls, and compared to experimental and micro-modeling results.Peer ReviewedPostprint (author's final draft

Numerical modelling of traditional buildings composed of timber frames and masonry walls under seismic loading

This is an Accepted Manuscript of an article published by Taylor & Francis Group in International Journal of Architectural Heritage on 2022, available online at: http://www.tandfonline.com/10.1080/15583058.2022.2033885Existing heritage buildings are often composed of diverse materials and structural typologies, representing a challenge for structural analysis tasks. This work investigates the combined use of simple Lumped Plasticity Models (LPM) and macro-mechanical Finite Element (FE) approaches to evaluate the seismic response of structures composed of timber frames and masonry walls. The calibration of these engineering models is derived from a wide set of nonlinear static analyses reproducing benchmark experiments on timber and masonry specimens. The LPM and FE models are used eventually to appraise the seismic response of two existing timber-masonry hybrid buildings, located in the historical centre of Valparaíso, Chile. The nonlinear analyses performed with these models predict the acceleration-displacement capacity of the buildings under seismic-like horizontal loading, revealing their potential local and global failure mechanisms.The authors gratefully acknowledge the financial support from the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU), the State Agency of Research (AEI), as well as the ERDF (European Regional Development Fund), through the SEVERUS project (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, ref. num. RTI2018-099589-B-I00). The first author gratefully acknowledges the ELARCH project (Euro-Latin America partnership in natural Risk Mitigation and protection of the Cultural Heritage, reference number 552129-EM-1-2014-1-IT- ERASMUS MUNDUS EMA21), funded by the European Commission, for the financial support of her predoctoral grant.Peer ReviewedObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.5 - Per a 2030, reduir de forma significativa el nombre de morts causades per desastres, inclosos els relacio­nats amb l’aigua, i de persones afectades per aquests, i reduir substancialment les pèrdues econòmiques directes causades per desastres relacionades amb el producte interior brut mundial, fent un èmfasi especial en la protecció de les persones pobres i de les persones en situacions de vulnerabilitatObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del mónObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.b - Per a 2020, augmentar substancialment el nombre de ciutats i assentaments humans que adopten i posen en marxa polítiques i plans integrats per promoure la inclusió, l’ús eficient dels recursos, la mitigació del canvi climàtic i l’adaptació a aquest, així com la resiliència davant dels desastres, i desenvolupar i posar en pràctica una gestió integral dels riscos de desastre a tots els nivells, d’acord amb el Marc de Sendai per a la reducció del risc de desastres 2015.2030Objectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.1 - Enfortir la resiliència i la capacitat d’adaptació als riscos relacionats amb el clima i els desastres naturals a tots els païsosPostprint (author's final draft

Nonlinear numerical modelling of complex masonry heritage structures considering history-related phenomena in staged construction analysis and material uncertainty in seismic assessment

This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. This material may be found at https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29CF.1943-5509.0001494.This paper presents the systematic use of numerical analysis as a tool for addressing some of the most common challenges encountered in the structural analysis of complex historical masonry structures, i.e. the description of the effects of history-related phenomena and the un-certainty of material properties. The numerical strategy is based on the use of a constitutive model able to describe time-dependent strain accumulation, as well as damaging behaviour un-der different stress states. This constitutive model is combined with a crack-tracking technique to represent tensile crack localization. The numerical model is applied to the study of two im-portant monuments in Spain, i.e. the Mallorca Cathedral and the church of the Poblet Monas-tery. The staged construction analysis of the first case study allows understanding the reasons of its current deformed condition, i.e. critical construction process, strain accumulation given by long-term creep phenomena, and nonlinear geometric effects. The structural analysis of the second case study allows the structural diagnosis of the existing deformation and cracking pat-terns given by architectural alterations, insufficient buttressing of the naves, and past earth-quakes. The application of a probabilistic analysis to the church of the Poblet monastery allows considering the effects of the uncertainties of material properties and numerical parameters in the seismic vulnerability assessment.The authors would like to thank the Ministry of Science, Innovation and Universities (MCIU) of the Spanish Government, the State Agency of Research (AEI) and the European Regional Development Fund (ERDF) through the SEVERUS project (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban cen-tres ref. num. RTI2018-099589-BI00).Peer ReviewedPostprint (author's final draft

Challenges, tools and applications of tracking algorithms in the numerical modelling of cracks in concrete and masonry structures

The final publication is available at Springer via http://dx.doi.org/10.1007/s11831-018-9274-3The importance of crack propagation in the structural behaviour of concrete and masonry structures has led to the development of a wide range of finite element methods for crack simulation. A common standpoint in many of them is the use of tracking algorithms, which identify and designate the location of cracks within the analysed structure. In this way, the crack modelling techniques, smeared or discrete, are applied only to a restricted part of the discretized domain. This paper presents a review of finite element approaches to cracking focusing on the development and use of tracking algorithms. These are presented in four categories according to the information necessary for the definition and storage of the crack-path. In addition to that, the most utilised criteria for the selection of the crack propagation direction are summarized. The various algorithmic issues involved in the development of a tracking algorithm are discussed through the presentation of a local tracking algorithm based on the smeared crack approach. Challenges such as the modelling of arbitrary and multiple cracks propagating towards more than one direction, as well as multi-directional and intersecting cracking, are detailed. The presented numerical model is applied to the analysis of small- and large-scale masonry and concrete structures under monotonic and cyclic loading.Peer ReviewedPostprint (author's final draft