Advanced Materials Research Vols. 133-134

Abstract: Compact Diagnostic Test (CoDiT) procedure allows one to test mechanical properties of historic materials in a minor destructive way using micro-cores drilled out of a masonry wall. CoDiT procedure applied to brick masonry gives insight into the non-homogeneity of material properties both at a brick and a wall scale level. The test site was the orthodox monastery in Supraśl, north-east of Poland. Micro-cores of 6 mm in diameter were drilled out using diamond core drill bits. The micro-core samples were used to prepare specimens for optical, mechanical and ultrasonic testing of brick properties. Material parameters were measured, including tensile, bending and compressive strengths and longitudinal wave velocity together with optical analysis of sample inhomogeneities. It is shown that all these measurements can be done using specimens made of a single micro-core. The correlation between various measured parameters and applicability of CoDiT to measurement of old brick strength are also discussed.

Abstract: One of the most well-known non-destructive methods for inspection and diagnosis in historical masonry walls is the flat-jack testing. Although it gives qualitative and valuable results about the local stress level and the deformability of the masonry material, when testing on irregular masonry walls, or walls with larger stone units, experimental and practical problems might occur, leading to inaccurate or useless results. In addition, the testing apparatus is labor, with difficulties in sawing task. Another limitation is the difficulty to test multi-leaves walls. To overturn these problems and to achieve more reliable information, an enhanced type of jacks is proposed in the paper. The new testing system consists of tube-jacks instead of the usual flat-jacks. As part of the preliminary research, analyses with FE models to simulate the differences between the conventional and the enhanced method are presented in the paper. The advantages and disadvantages of both methods are discussed and further research steps are presented.

Abstract: An automatic diagnostic monitoring system can guarantee the safety and integrity of a historic building. In this paper, we describe the long term application of a wireless sensor network (WSN) for permanent health monitoring in the Torre Aquila, a historic tower in Trento, Italy. The system consists of accelerometers, thermometers and fiber optic sensors (FOS) with customized wireless modules and dedicated software designed for wireless communication. The whole system was completed and started operation in September 2008, and data from the various sensor nodes are collected continuously, save during periods of system maintenance and update. Based on the first 1.5 years of operation in assessing the stability of the tower, the WSN is seen to be an effective tool. Modal analysis indicates that the tower has two independent structural parts. A comparison between the acquired long term deformation measurements and simulated numerical results shows good agreement. Monitoring of ambient vibration suggests that such vibration is not now a source of concern for the stability of the tower.

Abstract: A combined reaction of hydration and carbonation takes place in hydraulic lime and lime-pozzolana mortars. Hydration reactions are the first reaction and carbonation of lime is the complementary reaction in the strength gain. Competition between these two reactions can occur in lime-pozzolana mortars if the pozzolanic material has low reactivity with lime, leading to the consumption of lime by carbonation reaction. The degree and the order of these reactions are strongly influenced by the moisture content. Hydration reactions are enhanced under moist conditions while carbonation is delayed. Curing under dry conditions does not sufficiently increase their strength because the hydration reactions are slowed down or even terminated by the full carbonation of lime in lime-pozzolana mortars. The consequence of this on the mechanical properties of the mortars is remarkable while the same impact is not observed in their porosity. Such mortars require moist conditions to ensure sufficient strength development.

Abstract: The paper focuses on the structural analysis of monumental buildings, particularly upon the relationship between both instrumental measurements and the preliminary studies and the general comprehension of the construction history of each single building, including e.g. the historical evolution, materials, decay. A couple of case – study in the north of Italy are presented: the Trostburg Castle in South Tyrol and the S. Agata Church in Brescia. In these cases, cracks have been controlled by a long - time monitoring to investigate if structural damages could be influenced by the construction of underground galleries just near their foundations. The study focuses on the structural analysis of monumental buildings, particularly upon the relationship between both instrumental measurements and the preliminary studies and the general comprehension of the construction history of each single building, including e.g. the historical evolution, materials, decay. Collected data are discussed in comparison with the different approaches related to the knowledge of buildings, in order to evaluate limits and possibilities of proposed methods. Results underline how a deep investigation of an ancient and complex building, usually made up by a long time process of transformations and stratifications, allows to better understand the general structural behaviour. The strong comprehension of the constructive history of each single structure and a carefully discussed cracks board can provide a wider support to plan and make the diagnostic and structural investigation, e.g. this method helps in the choice of the type of tests and instrumentation to be employed and helps to localise where measurements should be taken, empowering the effectiveness of the results. Moreover, it allows to control and to understand results.

Abstract: Laser-induced fluorescence (LIF) is a powerful remote analysis tool that has been successfully applied to the real-time diagnosis of historical artworks, allowing the observation of features invisible to the naked eye, as pigment composition, biological attack and restoration technique. This paper presents a LIF-based optical radar and reports on the results of its deployment during a field campaign conducted in February 2010 in Seville, Spain.

Abstract: Historic masonries of the cultural heritage are aged and heterogeneous systems which are subjected to long-term exposition to the external environment. In such conditions, they can easily come in to contact with a consistent range of damaging agents, including water and salts sources. The related salt-induced damage is widely considered as one of the most dangerous decay process for their preservation. Conservative operations become therefore necessary and are performed with new materials that must fulfil specific requirements regarding their compatibility with the original ones and their resistance to damaging agents, especially in term of salt-resistance. The use of ready-mixed mortars in the restoration field has become a common practice and the number of commercial products currently available in the market is increasing. The present work reports the investigation on four types of ready-mixed mortars based on NHL binders and on two commercial NHL binders, together with the preliminary laboratory tests to assess the durability of mortar specimens to salt decay. The investigation provided useful information on the relationship between compositional and microstructural features and damage.

Abstract: This paper presents investigations of the wooden ceiling in the Leopoldinum Auditorium at Wrocław University (Poland). The investigations included: material, moisture content, mycological, resistographic, thermographic and dynamic load tests. The causes of damage to the valuable poly-chrome have been identified. A concept of conserving and strengthening the ceiling and the false vault is proposed.

Abstract: Timber is an intriguing structural material and the only one that is truly renewable. Being biodegradable, hygroscopic and non-isotropic, it presents special challenges when assessing its integrity in structures. The presented paper outlines the major issues related to in-situ evaluation of structural timber and summarizes the work of the RILEM Technical Committee 215-AST “In-situ assessment of structural timber”. The committee was established in 2005 to bring together leading scientists and practitioners in the field of evaluation of timber in existing structures. Timber structures have been investigated for decades using numerous techniques that have been either developed specifically for the material or were transferred from other fields of investigation. A state-of-the-art report describing existing and emerging technologies and methods was prepared by the RILEM committee. The report describes the principles, the applications and the limitations of major evaluation techniques for in-situ assessment of timber. A brief discussion of codes standards and future research needs shows that much needs to be done in this area. As a present activity, harmonized test procedure recommendations are being prepared that will provide the engineering community with valuable guidance when evaluating timber structures.

Abstract: The paper is related to the San Torcato Church, in Guimarães, Portugal. At the moment, the church has significant structural problems due to soil settlements. Cracks can be observed on the main and the lateral façades, the bell-towers are leaning, and the arches in the nave exhibit a failure mechanism with cracks and vertical deformations. Non-stabilized phenomena are present in the structure. To stabilize the damage, a structural intervention is planned to occur soon and the church is already monitored to follow the intervention. The paper clearly presents the problem with emphasis to the dynamic analysis carried out before the structural strengthening, namely: the experimental tests with output-only techniques for frequencies, damping and mode shapes estimation, FE model updating analysis and dynamic monitoring