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Old masonries are often affected by capillary water rise from ground, causing material deterioration and indoor discomfort. Moreover, the presence of water in the material pores influences the mechanical performance of the structure, to an extent which depends on the materials characteristics and which is still to be fully elucidated. The present paper is meant to give a contribution towards the quantitative assessment of the effect of moisture presence in masonry construction materials by means of mechanical tests on brick and mortar specimens. In particular, compressive strength and Young’s modulus of the specimens were experimentally measured both in dry and wet conditions. The results show that the effect of moisture is significant and greatly varies according to the microstructure of the materials in terms of both porosity and pore size distribution.

The “reinforced repointing technique” consists in replacing the mortar of existing horizontal joints of masonry with a material having high tensile strength. This technique permits to use composites thin pultruded laminae or steel textile sheets as reinforcing material, sealing the external part of joint to hide the application on the historical constructions. The main beneficial effects for a repointed masonry are a) and increased compressive strength and ductility, b) pseudo-vertical cracks are contrasted and c) the long term deformation (creep effects) are attenuated. In this study an analytical procedure is developed in the elastic range considering isotropic and orthotropic repointing materials. Results obtained from numerical simulations are also presented.

In this paper, a numerical study on the structural behaviour of three-dimensional cracked structures is presented. The compliance matrix of the cracked element is given by the sum of the compliance matrix of the intact element and an additional compliance matrix which contains all the flexibilities given by the presence of the crack. Crack depth and location are modelled as random variables in order to take into account the unavoidable uncertainty that always affects damaged structures. A simple and accurate method for the probabilistic characterization of the linear elastic response of cracked 3D frame structures with uncertain damage is developed.

In recent years, the evaluation of the conservation state of historic structures has drawn great attention from a wide range of professionals. Despite this, a complete and exhaustive guideline on this topic is not available and advancement on the diagnostic pathway to be followed for the assessment of historic masonry structures is still needed. The 7th FP EU Project SMooHS’s tasks included the enhancement of currently available diagnostic methodologies and the development of “smart” monitoring systems. In this paper, a multiphase and interdisciplinary approach proposed for the assessment of the health state of historical buildings is illustrated through a case study: Malvezzi Palace in Bologna, Italy. Considering both masonry and timber elements, a number of NDT and MDT techniques (sonics, ultrasonics, impact-echo, laser vibrometer, radar, thermography, acoustic emission, sampling for lab analyses, endoscopy, drilling penetration resistance, spectral analyser, wood moisture tester, ...) have been combined and integrated with advanced wireless monitoring systems.

A numerical approach has been recently devised for the modelling of falling rock protection barriers, metallic structures used as passive measures against rockfall. The paper assesses the reliability of the approach and explores its potential as a predictive tool, with reference to a specific barrier type.

A numerical strategy is developed to investigate the dynamic behaviour of falling rock protection barriers, metallic structures widely used as passive measures against rock fall. The modelling procedure is validated on a series of full scale impact tests carried out onto different barrier prototypes. Three numerical models were developed and analyses were carried out at various levels of impact kinetic energy. The paper presents some essential details of the numerical strategy as well as the main results, discussed with special emphasis to their relevance towards design.

Identification procedures based on dynamic testing have been extensively used to characterize tie-rods in a nondestructive manner. In general, the Young modulus of the rod, the applied tensile load, and the rotational stiffness of both the restraints are the sought parameters. To date, a procedure capable to identify all the above mentioned parameters has not been developed. In this work a strategy based on dynamic testing, added masses and Genetic Algorithms (GAs) is proposed. The framework estimates the unknowns by minimizing an objective function based on the discrepancy between the experimental and the numerical frequencies of vibration. Numerically, the frequencies are predicted for a given set of the sought parameters by a finite element based formulation. It is shown that by exploiting only few experimental frequencies of the tie-rod (principal system) along with those of some modified systems (dummy systems), that can be simply obtained from the principal system by adding a concentrated mass at a specific position along the rod, all the target parameters can be identified, even in the case of different rotational stiffnesses at the ends.

A procedure based on dynamic testing, added mass and Genetic Algorithms (GAs) aimed at the in situ structural characterization of tie-rods is proposed. It is shown that by exploiting only few experimental frequencies of vibration of the tie-rod (principal system S0) along with those of some modified systems (Si with i = 1, 2, · · · , n), that can be simply obtained from the principal system by adding a concentrated mass at a specific position along the tie-rod length, all the tie-rod structural parameters can be identified. In particular, the tie-rod Young’s modulus, the applied tensile load, the rotational stiffness at both restraints as well as the tie-rod material density are identified as the outcomes of an optimization procedure driven by GAs. The fitness function is defined as the discrepancy between the experimental frequencies of vibration of the systems Si and those numerically predicted for a given set of the sought parameters by a finite element based formulation. The value of the parameters is updated into the numerical scheme for the forward computation till the fitness function satisfies the required tolerance. Finally, in order to improve the statistics of the identifications, the Outlier Analysis, in which the discordancy test is carried out via the Mahalanobis distance, is applied to highlight eventual inconsistent identifications that can thus be discarded before the final estimation of the unknown parameters. The procedure has been applied to a metallic tie-rod at the ground floor in Palazzo Poggi (Bologna, Italy), seat of the Rectorate of the University of Bologna.

In this paper an approach that is able to derive the flexibility parameters in curved beams with an edge crack based on the strain energy density theory is presented. The method takes into account that the crack in a beam does not propagate in a collinear manner, but due to the presence of the mixed mode, it changes its direction. This allows a description of the phenomenon of the propagation of the crack similar to the experimental evidence. The crack is assumed to be radial before the loading, then it runs in the direction of the minimum of the strain energy density. Then, the crack is supposed to follow the direction of the principal tensile stress in the section. Preliminary results are presented for different position and initial length of the crack.

The rise of small cracks in masonry arches is not a sign of incipient collapse, but a resource that assures plasticity to the structure. This paper highlights the importance of these cracks, retracing the Jacques Heyman's theory from the hypotesis on masonry material to the safe theorem and the geometrical factor of safety

2006/2007 RIASSUNTO Nanocristalli e colloidi con un diametro compreso tra 1 e 100 nm, costituiti da materiali quali metalli, semiconduttori e ossidi metallici, sono tra gli “oggetti” più studiati negli ultimi anni grazie alle loro particolari proprietà ottiche, elettroniche, catalitiche. Tra questi le particelle metalliche, e in particolare le nanoparticelle di oro, sono tra i sistemi che suscitano maggiore interesse grazie alla semplicità dei metodi di sintesi, alla loro stabilità e alle interessanti caratteristiche osservate. Un importante esempio è costituito da nanoparticelle di oro protette da un monostrato di molecole organiche (MPCs, Monolayer Protected Clusters) che coniuga le proprietà tipiche di una nanoparticella metallica con le caratteristiche di un monostrato autoassemblato che, oltre a passivare la superficie di oro, può costituire un supporto ad una moltitudine di gruppi funzionali e biomolecole con potenzialità ancora inesplorate. La presente Tesi di Dottorato è focalizzata su due diversi progetti in cui il monostrato autoassemblato attorno alle nanoparticelle è in primo piano. Il primo riguarda lo studio delle proprietà del monostrato protettivo di MPCs. Ci si è proposti innanzitutto di investigare come l’organizzazione del monostrato dipende dalle dimensioni del nocciolo di oro. A tale scopo sono state preparate e caratterizzate nanoparticelle di oro idrosolubili MPC-C8-TEG di diverse dimensioni passivate dal tiolo anfifilico HS-C8-TEG. Avvalendosi della tecnica spettroscopica Electron Spin Resonance (ESR), è stata studiata l’interazione tra una sonda radicalica idrofobica e il monostrato di MPC-C8-TEG di 1.6 nm, 3.4 nm e 5.3 nm. In secondo luogo ci si è proposti di utilizzare nuovamente l’ESR per indagare in che modo un monostrato “misto”, costituito cioè da tipi diversi di tioli, sia organizzato da un punto di vista topologico. Si è pensato quindi a nanoparticelle idrosolubili protette da una miscela di due tioli anfifilici contenenti una porzione idrofobica di natura sufficientemente diversa, per esempio una alchilica e una fluorurata. A tale scopo sono stati progettati, sintetizzati e caratterizzati quattro nuovi tioli anfifilici contenenti una catena fluorocarburica e una catena oligoetilenglicolica di lunghezza crescente aventi la struttura riportata di seguito. Sono state sintetizzate e caratterizzate nanoparticelle idrosolubili protette da un monostrato omogeneo dei nuovi tioli anfifilici fluorurati e infine nanoparticelle idrosolubili passivate da un monostrato misto, a diversa composizione, del tiolo HS-C8-TEG (contenente la porzione alchilica) e dei tioli anfifilici fluorurati. Sono state quindi condotte misure ESR studiando l’equilibrio di complessazione di una sonda radicalica idrofobica e il monostrato di nanoparticelle protette da un monostrato omogeneo di tiolo fluorurato e di nanoparticelle protette da un monostrato misto tiolo alchilico/tiolo fluorurato. Il secondo progetto riguarda applicazioni di nanoparticelle di oro in catalisi eterogenea, in particolare per la preparazione di nuovi catalizzatori Au/CeO2 per l’ossidazione selettiva di CO in eccesso di idrogeno (PROX), condizioni che mimano quelle usate nella purificazione di idrogeno in celle a combustibile. Sono state messe a punto nuove metodiche di sintesi di catalizzatori contenenti nanoparticelle di oro, che sono stati caratterizzati e di cui è stata studiata l’attività e la stabilità in condizioni PROX, confrontandole con quelle di catalizzatori preparati secondo metodiche tradizionali. XX Ciclo 1979

A numerical analysis on the bending behaviour of thin shell, corrugated plates is presented in this study. A finite element analysis is performed to investigate the effect of initial geometry upon the salient features of the moment-rotation response.

The effect of bending prestress on the bistable behaviour of a tape-spring is investigated by specifying a thermal gradient through its thickness, in order to simulate residual bending. It is shown that the magnitude of the self-stress state which arises influences the bistability characteristics of the prestressed tape-spring.

This paper deals with a simple and reliable method for the probabilistic characterization of the linear elastic response of frame structures with edge cracks of uncertain depth and location in the three-dimensional setting. A numerical test evidences the performance of the approach.

This paper deals with a simple and reliable method for the probabilistic characterization of the linear elastic response of frame structures with edge cracks of uncertain depth and location. A numerical test enlightens the excellent performance of the present approach.

The approach by Siu and Bert and by Leissa that was originally developed for isotropic plates is extended to the problem of forced damped vibrations of functionally graded simply supported rectangular plates in the three-dimensional setting. Contrary to classical normal mode analysis, in this study the forced-vibration response is determined without prior solving the free-vibration problem. The solution is obtained by the Rayleigh–Ritz method, extended to include the damping term and the work done by the external excitation. Numerical results are presented for a two-phase graded material with a power law variation of the volume fraction of the constituents through the thickness. As a byproduct, the natural frequencies and the static solution are also determined. The dynamic response as well as exact natural frequencies of homogeneous plate are used to assess the accuracy of the present formulation. A parametric study with respect to varying volume fraction of the constituents and thickness ratio is conducted. The analysis is applied to predict the dynamic response of a functionally graded plate subjected to a harmonically exciting force on its top surface.

Due to the practical importance of functionally graded materials (FGMs) in various branches of engineering, Koizumi (1997), an increasing amount of attention has been devoted to different problems associated with the mechanical behavior of plates made of these materials, see, among the others, Reddy (2004). However, up to now the aspect of vibrations of such plates due to random excitation has not been investigated. Recently, Ferrante and Graham-Brady (2004) take into account the effect of random variations in both the component volume fractions and porosity for FGM plates subjected to deterministic thermal boundary conditions. Analysis of random vibrations is essential for engineers in order to ensure that the design of FGM components is reliable and safe. In fact, since FGM plates are widely employed in aerospace structures, they are often subjected to dynamic excitations of random nature in complex environmental conditions. Based on the above remarks, in this work a preliminary study on the response characteristics of FGM plates to random loading in the three-dimensional setting is presented. Material properties, namely, modulus of elasticity and mass density, are assumed to follow a through the thickness variation according to a simple power law distribution in terms of the volume fraction of the constituents. The plate is assumed to be all round simply supported. A three-dimensional Ritz energy approach is employed in the free vibration analysis. Once the natural frequencies and mode shapes have been determined, the transient response is studied by the modal superposition method. It is assumed that the plate under study is subjected to a stationary random excitation with given mean and correlation function. Displacements and external forces are expressed in terms of series of approximate modes of vibration, which satisfy the boundary conditions, Elishakoff (1999). Analytical expressions for the distribution of the mean-square displacement and autocorrelation function of the response are found. Preliminary numerical results are presented in tabular and graphical format for the natural frequencies and dynamic response of aluminum/zirconia square plates. The approach seems to be suitable for the computationally intensive task of three-dimensional modeling due to ease of generation and numerical implementation. Three-dimensional solutions for functionally graded plates are useful because they can be used as benchmarks to assess the accuracy of various two-dimensional theories.

Analytical solutions to problems of solids mechanics are useful to test the accuracy and the precision of the numerical approaches. Problems such as shear locking or boundary layer can be better understood with the help of analytical solutions. However, it is known that only simple cases can be solved by hand. Furthermore, some cases which are theoretically solvable can also result in rather tedious analysis. Nowadays computer and mathematical software development allow to avoid this problem if they are associated with a suitable formulation. Classical formulations of mechanics of elastic body solve each particular problem by obtaining standard differential equations but generally do not give a unified method to solve them. In this paper a non-standard formulation is applied to find analytical solutions for elastic plates considering shear deformation (Reissner-Mindlin model) using a computer-aided approach. In addition, the results are compared to finite element model predictions. The main advantage of the proposed methodology over classical approaches is that it can be applied to problems of structural mechanics that are radically different using the same matrix framework, similarly to the FEM. Therefore, a computer-aided approach is used to obtain the analytical solution. This unified formulation is described Tassinari et al. [6]. The Reissner-Mindlin model (Reissner [3], Mindlin [4]) takes into account the shear deformation and it is generally recommended for moderately thick plates whereas Love-Kirchhoff model is more suitable for thin plates (Kirchhoff [1], Love [2]). The derivation of the governing equations of the RM plate results in a system of partial differential equations. The Levy solution technique can be used (Timoshenko and Woinowsky-Krieger [7], Szilard [5]) once the boundary conditions on two opposite edges are given. The solution is written as a series of orthogonal functions of the first coordinate multiplied by unknown functions of the second coordinate. The governing system is reduced to a system of ODEs that applies for each unknown term of the series. The application of the unified formulation to the Reissner-Mindlin plate results in a governing system of ODEs written in a matrix canonical form (see Tassinari et al. [6]). This expression is characterized by the state vector, which contains the generalized stresses and displacements, and the system matrix which describes the equilibrium. It is shown that this form can be applied to several problems of structural mechanics, by consistently adapting both system matrix and state vector. In this paper, the case of the Reissner-Mindlin plate problem with simply support on two opposite edges is solved. The analytical solution for a particular load case is presented showing the differences between the Reissner-Mindlin solution and the predictions given by the Love-Kirchhoff model (Kirchhoff [1], Love [2]). Finally, the vertical displacement field obtained analytically for different thickness-to-side ratios is compared with finite element method predictions. The analytical solution carried out shows the effect of the shear deformation in plate with small slenderness. In particular, the magnitude of this effect is significant for the vertical displacement. In general, the other components of the state vector are not significantly influenced in the domain of the plate but exhibits perturbations close to the edges. This edge effect is known as boundary layer and further investigations are needed considering higher-order terms. The results obtained from the proposed analytical method and numerical models presented in this study are comparable. Furthermore, the finite element analysis carried out shows that for a reasonable mesh refinement the numerical models used give excellent approximation of the analytical solution. Keywords: analytical solution, unified formulation, shell, plate, Reissner-Mindlin, Love-Kirchhoff, shear strain, finite element. References [1] Kirchhoff G., Über das Gleichgewicht und die Bewegungen einer elastischen Scheibe. Journal für reine und angewandte Mathematik, 1850; 40; 51–58. [2] Love, A. E. H., A treatise on the matematical theory of elasticity, Dover, 1944. [3] Mindlin R. D., Influence of rotatory inertia and shear on flexural vibration of isotropic, elastic plates. Journal of Applied Mechanics, 1951; 18; 31–38. [4] Reissner E., The effect of transverse shear deformation on the bending of elastic plates, Journal of Applied Mechanics, 1945; 67; A69-A77. [5] Szilard R., Theories and applications of plate analysis: classical, numerical and engineering methods. Wiley, 2004. [6] Tassinari L, Monleon S, Gentilini C, Ubertini F. A unified approach for analytical solution of moderately thick shells and plates. (Paper in preparation). [7] Timoshenko S, Woinowsky-Krieger S. Theory of plates and shells. McGraw-Hill, 1959.

A significant portion of the building stock in seismic regions all over the world is constituted by brick masonry structures that are well known to be prone to damage under seismic excitations. For evaluating the dynamic performance of masonry buildings, efficient numerical models are required. In this paper, considering the typical hysteretic behavior of brick masonry walls, a unified model for the static and dynamic analysis of masonry structures governed by ten key parameters is proposed. The model is able to simulate different kinds of walls such as unconfined unperforated and perforated walls, as well as confined unperforated and perforated walls subjected to horizontal reverse cyclic loadings and vertical compression. The identification procedure of each key parameter, that includes, among the others, lateral strength, loading and unloading stiffness, accumulated damage factor, shrinkage factor, as well as slipping factor, is presented by analyzing over one hundred results collected from literature. In order to validate the proposed approach, four different types of wall specimens were tested under cyclic loads. Furthermore, a two-storey half-scale structure was tested to verify the effectiveness of the presented model in reproducing the deformation response and global hysteretic behavior of the structure.

Mixtures of fluorinated and hydrogenated compounds display peculiar properties arising from their mutual phobicity and the same applies to semifluorinated species in which a reciprocal phobicity pattern exists within the same molecule. The interest in assemblies comprising these species stems from the ease in which self-sorting can take place, allowing the preparation of compartmentalised molecular aggregates with unique hydrophobic patterns or surface features. Most importantly, this is the result of molecular properties rather than specifically designed fabrication techniques. This brief overview describes some examples that are instrumental to present the features of fluorinated/hydrogenated supramolecular assemblies in which self-sorting of the dislike units takes place at different length scales. This review is focussed on flat assemblies such as self-assembled monolayers on gold surfaces, Langmuir Blodgett films and on three dimensional assemblies such as micelles, vesicles and nanoparticles.

In this paper, the preliminary results of a series of pull-out tests conducted on mortar cylinders with embedded bars are presented. The bars are made of high strength stainless steel and are of helical shape to increase mechanical interlocking with the surrounding mortar. Usually, such bars are employed in situ to realize structural repointing in the case of fair-faced masonry walls. To this aim, they are inserted in the mortar bed joints of masonry for providing tensile strength to the walls and with the function of crack stitching. The aim of the present experimental tests is to determine the bond-slip relationship for bars embedded in masonry. Firstly, pull-out tests are conducted on mortar cylinders considering different embedded lengths of the bars. Further tests are on-going on masonry specimens with bars embedded in the mortar joints. An analytical investigation is also carried out for the interpretation of the pull-out test results.

In this study the results of an experimental campaign that involves masonry specimens subjected to a purposely designed splitting test are presented. The specimens are reinforced in the mortar joints by means of carbon bundles impregnated with a water based resin. Unreinforced specimens are also tested for comparison purposes. Some specimens are characterized by an initial crack obtained artificially by cutting the bricks to highlight the crack arrestor function of the carbon bundles. Results show that the failure mechanism from brittle becomes ductile and a load bearing capacity increment is registered in reinforced specimens.

Harnessing the reciprocal phobicity of hydrogenated and fluorinated thiolates proved to be a valuable strategy in preparing gold nanoparticles displaying mixed monolayers with a well-defined and pre-determined morphology. Our studies display that the organisation of the fluorinated ligands in phase-separated domains takes place even when these represent a small fraction of the ligands grafted on the gold surface. Using simple model ligands and by combining 19F NMR or ESR spectroscopies, and multiscale molecular simulations, we could demonstrate how the monolayer morphology responds in a predictable manner to structural differences between the thiolates. This enables a straightforward preparation of gold nanoparticles with monolayers displaying stripe-like, Janus, patchy, and random morphologies. Additionally, solubility properties may be tuned as function of the nature of the ligands and of the monolayer morphology obtaining gold nanoparticles soluble in organic solvents or in aqueous solutions. Most importantly, this rich diversity can be achieved not by resorting to ad hoc developed fabrication techniques, but rather relying on the spontaneous self-sorting of the ligands upon assembly on the nanoparticle surface. Besides enabling control over the monolayer morphology, fluorinated ligands endow the nanoparticles with several properties that can be exploited in the development of novel materials with applications, for instance in drug delivery and diagnostic imaging.

This paper proposes an effective design approach for quickly determining the specification, size and amount of components of a flexible rockfall protection barrier structure. The approach is based on a reliable numerical modelling validated by several experimental tests that include both component tests and full-scale impact tests. The interception structure made up of a steel wire-ring net is accurately investigated through a series of in-plane and out-of-plane quasi-static tests carried out on net specimens, to define the ring constitutive model and failure criterion. The accuracy of the numerical strategy for an overall barrier structure with nominal energy level of 1500 kJ is validated by a full-scale in-situ test including service energy level (SEL) and maximum energy level (MEL) impacts, according to the European guidelines. From the numerical models, it is inferred that the total energy of the impact is simultaneously dissipated in different ways, where the internal energy of the structure plays a significant role. The distribution of the absorbed energy among the different barrier components is explored and defined by means of the developed finite element model. Besides, the design values of the internal force in the ropes are derived with an adequate safety margin. The proposed design procedure, applied to a barrier structure with nominal energy level of 3500 kJ, is assessed by a full-scale impact test, proving that the design approach is reliable and efficient.

Fiber-reinforced composites with inorganic matrix (FRCMs) have been recently proposed as a more compatible and durable route to strengthen masonry structures with respect to FRPs (fiber-reinforced polymers), but their weathering mechanisms in aggressive environments are still scarcely known. In this paper, brick masonry specimens were reinforced with FRCM strips, made of galvanized steel fibers embedded within a hydraulic lime-based mortar, and were subjected to an artificial weathering procedure designed by the authors, involving capillary water absorption and salt crystallization cycles. Finally, direct shear tests were performed on the FRCM-masonry joints. To reproduce conditions that may be found in real buildings, shear tests were also carried out after applying the FRCM composite on salt laden masonry blocks. Interfacial debonding behavior was interpreted based on the salt distribution within the masonry joints and the porosity of materials. The permeable matrix did not hinder the migration of the saline solution used in some cycles, which in turn resulted in no significant accumulation of salts beneath the composite strip, and no micro-crack opening in the composite after accelerated weathering. Some corrosion of the galvanized steel cords in presence of high amount of chlorides was observed in the composite.

A school building, located in Bomporto (Modena, Italy) and hit by the Emilia-Romagna Italian earthquake in 2012, has been investigated in the paper. The seismic vulnerability of the building has been evaluated by means of non-linear static analyses, which have been carried-out through the 3MURI calculation program. The comparison between the damage state produced by the earthquake and the simulation results put in evidence the reliability of the numerical analysis. On the basis of the detected seismic deficiencies of the damaged building, a structural reinforcement intervention of masonry walls has been designed by means of either FRP strips or steel ones. Finally, a parametric analysis by varying the material and the geometrical configuration of the FRP intervention (width and spacing of the strips) has been performed with the purpose to identify, through a cost-to-benefit comparison, the optimal retrofitting solution.

This International Conference, MuRiCo5, was organized by AICO under patronage and sponsorship of DICAM Department of University of Bologna and patronage of University IUAV of Venice, University of Roma Tre, University of Wroclaw and University of Miami. It represents a forum to promote and exchange latest theoretical, computational and experimental research works finalised to the design of structural strengthening of historic masonry constructions.

In this paper, preliminary results of an experimental campaign carried out on masonry triplets subjected to weathering cycles in salt solution are presented. Weathering cycles are constituted of a wetting phase by capillary rise of a sodium chloride solution and a drying phase in oven. At the end of the last conditioning cycle, triplets are shear tested in order to quantitatively assess the effects of salts on their mechanical behaviour, in particular on the Mohr-Coulomb relationship. To this aim, three levels of pre-compression are applied during the shear tests. For comparison purposes, unconditioned triplets are also tested under the same loading conditions.

In this study, confined masonry specimens with regular arranged openings are tested in order to study the influence of different enhancements of the columns on seismic failure modes. In particular, five brick masonry walls and three half-scale two-storey masonry structures are tested under quasi-static loads. The experimental results show that increasing column ratio improves the seismic behavior of the wall specimens to some extent, but an excessive reinforcement ratio of the columns decreases the ductility. The global failure mode of the two-storey masonry structures is modified by inserting iron wires in the mortar bed joints, improving the structural collapse resistant capacity effectively.

Fiber-reinforced cementitious matrix (FRCM) composites have been recently employed as a strengthening system to retrofit historic masonry structures, since they are more compatible with masonry, less subject to ageing, and compliant with conservation criteria for cultural heritage than fiber-reinforced polymer composites. However, the durability of FRCMs, such as the resistance to salt attack, has not been deeply investigated yet. In this paper, the mechanical behavior of steel FRCM strips bonded to fired-clay brick masonry blocks is studied experimentally. Single-lap shear tests are conducted in laboratory on control FRCM-masonry joints and on additional joints that underwent artificial weathering cycles in a solution of sodium sulfate decahydrate. Peak loads, slips at failure at the loaded end as well as failure modes are investigated. Pore size distribution of the constituent materials and the amount and distribution of salt within the specimens are reported and discussed in order to evaluate the transport and crystallization mechanisms of sulfate in masonry elements strengthened with externally bonded FRCM strips.

In this paper, a literature review on diagonal compression tests conducted on masonry elements reinforced by means of structural repointing technique is presented. This strengthening technique usually consists of placing in the mortar bed joints, high-tensile strength materials in the form of rods, strips, laminates or bars to increase the ductility and the overall mechanical performance of the structure. Being the reinforcing materials completely hidden after application, this system is particularly suitable for fair-faced masonry structures and historic buildings. In this paper, the main advantages and limits achieved by using reinforced repointing technique as shear strengthening system are investigated.

ESR spectroscopy has been used to study the interaction of para-pentylbenzyl hydroxyalkyl nitroxide with the monolayer of water-soluble protected gold clusters having a core diameter ranging from 1.6 to 5.3 nm. The solubilization of the nitroxide probe in the more hydrophobic environment of the monolayer strongly depends on the size of the gold core. In particular, the partition equilibrium constant increases as the nanoparticle diameter decreases. These results have been attributed to the different packing of the chains in the monolayer resulting from the different radius of curvature of the investigated nanoparticles. This represents, to the best of our knowledge, the first report demonstrating that the core size of metallic nanoparticles affects the solvating properties of the protective organic monolayer.