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[EN] After the collapse of some heavy buildings and towers in Italy and elsewhere, the hypothesis of possible continuous damage to these structures due to the dead and cyclic loads (wind, temperature variations, etc.) has been formulated by the authors. The long term behaviour of historic masonry has also been detected by laboratory creep and cyclic tests. The results indicate that a laboratory and on site investigation together with analytical modelling are important peculiarly for tall bell-towers. The application of these procedures on the Bell-Tower of the Cathedral of Monza is here reported and discussed., [ES] Tras el colapso de varios edificios de fábrica y torres en algunos países como Italia, los autores han formulado la hipótesis de un posible deterioro continuo de dichas estructuras debido tanto a las solicitaciones derivadas del peso propio como de las cargas cíclicas (viento, variaciones de temperatura, etc). El comportamiento a largo plazo de la mampostería histórica ha sido también objeto de estudio mediante un seguimiento continuo de ensayos en laboratorio y la aplicación de pruebas cíclicas. Los resultados indican que una investigación, tanto en laboratorio e in situ, sumada a una modelización analítica puede resultar fundamental en casos de campanarios de cierta altura. A continuación, se propone la aplicación de dichos procedimientos en el Campanario de la Catedral de Monza., La investigación ha sido apoyada por el CNR-GNDT, MURST y la parroquia de Monza. Los autores desean agradecer a los Srs. P. Perolari, G. Ghilardi, M. Cucchi, M. Antico, C. Arcadi y M. Iscandri por su ayuda y colaboración en el trabajo experimental tanto in situ como en laboratorio.

The research is part of a larger project, within an international cooperation, supported by UNESCO, for the study, restoration, and revitalization of Byzantine and Ottoman monuments in Southern Albania. The project was carried out on the Saint Nicholas monastic complex located in the Mesopotam area (Albania) by a multidisciplinary group of researchers from different Italian universities. Using integrated surveying technologies, the diagnostic investigation focused on enhancing our knowledge of structural behavior as a qualifying element for future conservation and maintenance programs. The aim was to develop interpretive models able to connect thematic and geometric information to the history of the monument by reading and recognizing the constructive technologies that were employed. Hence, the term “surveying techniques” includes geometrical surveys by laser scanner and photogrammetry, stratigraphic analysis, crack pattern surveys, and crack monitoring. The study was carried out on the Church of Saint Ni...

Creep and the creep-fatigue interaction have shown to strongly influence the mechanical behaviour of ancient masonry and long-term heavy loads proved to cause a continuous damage. The problem of achieving a reliable life-time estimate of historic masonry toward the effects of persistent loading has been dealt with by a probabilistic approach. The results of pseudo-creep tests on ancient masonry of different ages and their interpretation through a probabilistic model are presented, aimed to the individuation of a random variable as a significant index of vulnerability, and to the solution of the classic problem of reliability in stochastic conditions.

This paper presents and discusses the results of investigations carried out by the authors on two castles that are considered as case histories within a project financed by the European Commission (project EVK4-2001-00091 ONSITEFORMASONRY), coordinated by C. Maierhofer of Bundesanstalt für Materialforschung und prüfung (BAM), Germany. An extensive investigation programme (including sonic, radar, flat-jack, coring, boroscopy, etc.) was planned to support the preservation and restoration actions of two ancient castles. The experience from this investigation shows the importance of the diagnosis project in selecting the most relevant strategies and tests for each specific problem.

A nonlinear finite element model was developed to simulate the nonlinear response of three-leaf masonry specimens, which were subjected to laboratory tests with the aim of investigating the mechanical behaviour of multiple-leaf stone masonry walls up to failure. The specimens consisted of two external leaves made of stone bricks and mortar joints, and an internal leaf in mortar and stone aggregate. Different loading conditions, typologies of the collar joints, and stone types were taken into account. The constitutive law implemented in the model is characterized by a damage tensor, which allows the damage-induced anisotropy accompanying the cracking process to be described. To follow the post-peak behaviour of the specimens with sufficient accuracy it was necessary to make the damage model non-local, to avoid mesh-dependency effects related to the strain-softening behaviour of the material. Comparisons between the predicted and measured failure loads are quite satisfactory in most of the studied cases.

Aim of this research was to evaluate the possible application of the AE technique to study the response of multiple leaf masonry repaired with different techniques. The results of shear tests carried out on three specimens repaired after failure are presented on an explorative basis; on two of them the acoustic emission (AE) technique was also used. Through a number of sensors and by triangulation, this technique makes it possible to identify the location of the damage, unknown initially, and subsequently to assess the stability of its evolution. Using the AE technique the area of the material where the cracks propagated during shear tests was identified. These analyses made it possible to evaluate the effectiveness of repair interventions through parameters other than stress and strain, and contributed to the identification of the most suitable methodology for their optimisation.

The paper analyses the most recent research carried out in Italy concerning the seismic behaviour of historic buildings. The last Umbria (Italy) earthquake in 1997 was an interesting on site test for the evaluation of the repair and prevention techniques applied to masonry building of historic centres in seismic areas, but also of the structural modelling. Most of the situations examined made important contributions to a general re-thinking of masonry evaluation and strengthening. The great importance in the mechanical behaviour of a building of building rules and of structural details, as well as transformation phases has been demonstrated.

The scope of Rilem Committee TC167-COM is the characterisation of old mortars, with respect to their repair. For damage analysis of historic buildings, the characterisation of the old mortars may represent an essential part of the investigations. This statement can also be inverted, keeping in mind the scope of the committee and more specifically the second part ‘with respect to their repair’. It is essential to have knowledge of the condition of the old mortar and of the causes of any decay that has occurred (VAN HEES et al., 2000). The aim of this article is to underline the importance of knowledge on the factors that influence the way in which degradation of materials- and especially mortars in monuments - occurs. The most common forms of degradation of mortar in monuments, as well as the type of investigation, which is necessary to understand the cause of the damage, are described. On the basis of the assessed decay form and decay process, the most adequate repair method and the most suitable repair mortar can be chosen. The diagnosis of the damage is very often forgotten in practice, even though this is a fundamental step to guarantee a compatible and durable restoration. Such negligence can lead to major incompatibility problems in the case of repair mortar application. The approach discussed in this document can result in a better understanding of the causes of incompatibility and in guidelines for compatible repair mortars, based on the specific conditions of the individual monument. This article describes the approach, as proposed by Rilem TC167-COM .

In the last 30 years, the restoration of our cultural heritage has become common practice. Initially, only very important monumental buildings were saved and restored, while the rest were demolished and replaced. Then historic centres and groups of buildings were protected, preserving all structures in a reaction to the previous systematic spoiling of the cultural heritage. Subsequently, it was recognized that all urban structures, including small dwellings, should be respected and preserved with great care. Nowadays, this respect for old buildings means finding out every detail of their architecture, fabric and structure. The importance of controlling the efficacy of the techniques of repair and improvement is appreciated[1]. This article attempts to provide a state-of-the-art review of the European, and in particular the Italian, attitude towards the reuse of historic buildings with the help of some case histories.

An experimental research on of masonry has been carried out. Thermal cycles and salt crystallization test were carried out on solid brick samples and small masonry assemblages, using bricks and mortars produced in Italy and in Poland. The specimens were strengthened with CFRP textiles or laminates in different configurations. To perform thermal accelerated ageing tests, specimens were subjected to a temperature variation ranging between −10 and +70 °C, applied cyclically. The procedure was validated during testing. The results showed the influence of the properties of the adhesive and of the strength of the brick in the failure of specimens. As for salt decay tests, a RILEM pre-standard procedure was followed to evaluate the resistance of tested materials to sulfates. Damage evolution was monitored by visual observation and by quantification, at each 4-week cycle, of material loss by a laser profilometer. The results showed the rising of salt from the uncovered surface as from the first week of observation, and also a concentration of stresses underneath the fibres. The pull-off test was chosen as reference test, in order to the loss of bond. The durability was also checked on reference unreinforced specimens. Pull off tests were carried out on the surviving specimens at the end of the tests. The results among the various series of specimens are compared. This costly repair technique can show adhesion problems due to humidity and high temperature.

The authors applied sonic tests to study the propagation of sonic waves through stone masonry walls. In particular, tests were made to study the effect of the joints and the influence of the characteristics of the stones surface, rough or smooth, on the measurement of the sonic velocities on granite masonry specimens. A series of direct, indirect, and impact echo sonic tests were performed on single stones and on columns of stones with dry and mortar joints to obtain P- and R-wave velocities. The results allowed a better understanding of the influence of the stones characteristics and the samples geometries, namely the number of joints, to the global response of the masonry to the propagation of sonic waves. This study also allowed verifying the complementarity of the different sonic test configurations and the interest to cross information from more than one technique to obtain more reliable information. Finally, significant results were also achieved concerning the relationship between the parameters obtained for P and R waves.

In conservation practice, operations aiming to restore structural functionality of historical buildings are of primary relevance. Partial rebuilding, the substitution of damaged bricks or blocks and the integration of deteriorated joints are, among others, interventions that require the introduction of new materials in a heterogeneous and aged masonry system. An appropriate durability of these interventions can only be assured if a deep knowledge of the original materials and of their state of conservation is combined with reliable understanding of the behaviour of new materials introduced. The present paper reports the results of the investigation of four commercial ready-mixed mortars based on NHL binders. The mineralogical composition of each product has been evaluated by XRD and polarization-and- fluorescence microscopy (PFM). The molecular composition of the mixes has also been evaluated by FTIR spectroscopy and the morphological features have been studied by SEM observations. The mechanical behaviour has been tested as well. Although supposedly comparable products, the mortars show different compositional features, microstructures, additives and mechanical behaviour. These are essential to evaluate compatibility with historic materials, and should be stated on the technical data sheets, or be determined. © 2009 WIT Press.

This paper describes a procedure, addressed to an articulated knowledge of the material, of the morphology and of the constructive aspects of the masonry structures, of the mechanical behaviour and of the possible failure mechanisms of complex buildings in Sulmona (AQ), an important historic centre in Central Italy. It is an area of great interest, not only considering its seismic history, but also because of the characteristics of its prestigious buildings, mainly made of multiple leaf stone masonry. The understanding of the historical buildings has made use of a direct survey of the constructions (based on a geometrical survey, on a survey of the materials and of their state of damage), of indirect information deduced by documentary sources, and of data collected through in-situ non destructive or minor destructive testing and laboratory investigation for a chemical, physical and mechanical characterisation of the masonry and of its components. Record templates and forms, some of them purposely set up, have been adopted and collected into a database for the damage and masonry quality assessment and the evaluation of the future vulnerability of the buildings to in-plane and out-of-plane actions according to damage abacuses previously produced.

To apply conservation principles to archaeological remains is a difficult task, especially when they are in a state of ruin due to destructive events, such as earthquakes, floods, storms, etc. or, even worse, wars. This was the case of the Hindu temples of the archaeological site of My Sơn (Vietnam); the temples were built by the Cham people from the 5 th to the 14 th century A.D., partially destroyed during various invasions from China and during wars between the Chams and the Kmers and finally badly damaged by shells during the Vietnam war.

Masonry presents some inadequacies due to its almost total lack of tensile strength. Typical damage to multiple leaf walls during earthquakes is the loss of bond between the leaves with consequent collapse of the external leaf. Retrofitting or repair of this damage is a very difficult task. In many cases grout injection or wall jacketing fail due to incompatibility with the construction technique of the walls.\ud \ud A complementary technique to the grouting has been proposed by the authors. Experimental results and applications of the technique on site have shown positive characteristics and the results of tests carried out on site show, in some cases, increases in shear strength and stiffness of the masonry walls.

Strategies and methodologies for the assessment of historic masonry structures based on non-destructive and minor-destructive testing methods were developed in the European Research Project ONSITEFORMASONRY and were successfully applied to assess the structure and material properties of selected structural elements in the Altes Museum in Berlin-Mitte. For the planning of a broad reconstruction within the framework of a master plan concerning the whole of Museum Island in Berlin, several questions arose which are also typical for other historic structures in general, thus the Altes Museum was chosen as a pilot site for the validation of non-destructive testing methods.

In view of preserving the historical heritage, the deterioration processes of masonry materials and the long term damage of multiple leaf historic buildings is studied from an experimental and a numerical point of view. Durability tests and pseudo-creep tests have been carried out and interpreted through probabilistic models for the service life prediction. The precocious recognition of structural critical states will allow to design repair and strengthening interventions and to prevent total or partial failure of the constructions.

A finite element model was developed to analyse the Byzantine Basilica of San Vitale in Ravenna (Italy); modelling is intended to help understanding the origin of a diffused crack pattern in the building. In the structural analyses, account was taken of the permanent loads and the seasonal thermal changes. Owing to the complexity of the geometric model, a simplified (linearly elastic, isotropic) constitutive law had to be assumed to keep the computing time within reasonable limits. Accordingly, the adopted constitutive law cannot fully explain the surveyed crack pattern, which is influenced by the brittleness and the anisotropy of the constituent materials; thus, the performed analyses constitute only a first step towards the understanding of the structural behaviour of the Basilica. It is shown, however, that the self-weight alone is largely responsible for the current state of damage in the Basilica. The numerically predicted seasonal change in displacements agree fairly well with the measurements of a monitoring network taken every six months, which proves the reliability of the finite element model.

Predicting the behaviour of multiple-leaf masonry walls is a challenging issue, given the influence of a wide range of factors as the mechanical properties of the leaves, the leaves dimensions and the way the leaves are connected to each other. In the present paper, novel experimental results in large three-leaf wallets subjected to shear and compression are introduced together with a careful numerical interpretation. Two types of collar joints (with and without shear keys) and two types of stone (weak limestone and strong sandstone) are considered in the tests. The influence of the boundary conditions on the numerical response is thoroughly investigated and good agreement with the experimental results is found. Moreover, a discussion on simplified calculations for practical assessment of existing walls is addressed., Portuguese Foundation for Science and Technology - SFRH/BD/5002/2001., MURST - cofin. 2000/2002.

The Cathedral of Noto, one of the most important baroque monuments that has given notoriety to the town of Noto, collapsed in the 13th of March 1996, approximately 5 years after the earthquake of ‘Santa Lucia’ that took place in December 13th 1990. The collapse has pointed out serious deficiencies in constructive materials of pilasters, even in their capacity to support vertical loads. That is why the earthquake of 1990 has acted as ‘the last blow’, coming after a long period of fatigue. Instead, the geometry of the church results to be ‘good’, and for this reason the reconstruction design consists merely in new pilasters, well made with local material, the well known ‘pietra di Noto’ and the replacement is going to take place both on the right, in the place of the collapsed pilasters, and on the left, in substitution of the old pilasters, really not adaptive for restoration. In this way, and with few other interventions, the ‘new’ church should result capable to resist to earthquakes similar to the one that occurred in 1693.

[EN] Restoration of heritage masonry buildings was in the past, until the sixties, a job for a few experts. Damage to historic buildings due to earthquakes and decay due to lack of maintenance and ageing have now implicated a large number of architects and engineers in restoration design; as a consequence there is a great need for guidelines and codes for testing and application of various techniques for preservation as well as for training and teaching. On the following pages, the main recomendations, existing codes∫, development and future necessities are presented., [ES] La restauración de edificios históricos de obra de fábrica, fue, hasta los años setenta, algo reservado para unos pocos expertos. El deterioro de este tipo de construcciones, debido a los últimos sismos, a la carencia de mantenimiento y a su propia antigüedad, ha involucrado en la restauración a un gran número de arquitectos e ingenieros; como consecuencia, se plantea una gran necesidad de guías y códigos para la realización de ensayos, la aplicación de técnicas para la conservación, así como la práctica de la enseñanza. A continuación se presentan las principales recomendaciones, los códigos existentes, el desarrollo y las necesidades de futuro.

A cable (such as in a submarine energy-transmission line) is supposed to be subjected to given transversal loads and a given tension force, in the vicinity of a frictionless rigid ground of known profile. The search for its equilibrium configuration is a contact (unilateral support) problem of a special kind. The problem is studied here with reference to a finite difference discretization of the system, under the small deformation hypothesis. On this basis its formulation becomes a linear complementarity problem or, alternatively, a quadratic, strictly convex program. Extremum properties of the solution are established and interpreted in mechanical terms. A general monotonicity property of the equilibrium configuration under proportional loading is pointed out; precisely, it is proved that, despite the nonlinearity of the system, whatever the load distribution, as the load factor increases, in any point of the cable the possible contact reaction and the vertical distance from the obstacle will never decrease. Among the mathematical programming algorithms presently available, Cryer's systematic overrelaxation is found to be efficient for the numerical solution of large-size problems of the type in question. Some numerical experience is presented.

Masonry structures subjected to aggressive environment may suffer degradation during their service life; the decay strongly depends on type of the component materials and the technique of construction. This can lead the structure to high states of damage even if not failure. The great randomness connected with the occurrence of critical attacks suggests approaching the deterioration process of masonry under a probabilistic point of view. Following this way, the deterioration process L(t) of stone masonrics has been carried out. It has been approached as: 1) L(t) time dependent stochastic process of the random variable (r.v.) l. 2) L(t) time dependent stochastic process of the r.v.τ.