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Highlights • Historical timber-framed wall system was investigated under cyclic loads. • Damage progression and post-elastic behaviour was analysed by image-based tracking method. • Plastic deformations and local damage occurred in some joints. • Observations are important for the design of strengthening or repair interventions. Abstract The scope of this paper is to analyse local phenomena associated with the damage progression and post-elastic behaviour of a historical timber-framed wall system under cyclic loads. It was assessed on series of points identified on the wall by processing time-resolved sequences of images. Dedicated methodology of image-based tracking method was developed to analyse local phenomena, such as relative displacements, rotations and deformations in the wall. It was possible to deduce that plastic deformations and local damage occurred in some joints. This type of observation is important for the design of rigorous strengthening or repair interventions. [ABSTRACT FROM AUTHOR]

Timber structures can undergo alteration during their service life, which can be caused by mechanical, environmental or biological agents (bacteria, fungi and insects), because of the biological nature of the material. On site characterization of timber members is a very challenging task, especially assuming that both, the structure itself and material used for construction have to be evaluated. Current assessment procedures are limited to visual inspection, occasionally supported by a few instrumental analyses (such as wood moisture content measurement and drilling resistance tests). However, a clear tendency for the application of various non-destructive techniques is observed nowadays. The paper presents an overview on the current applications of infrared spectroscopy for the characterization of various alteration phenomena in wooden artefacts. A literature review is complemented by a series of results, reported from experimental campaigns carried out by the authors. The aim of the paper is to demonstrate the applicability of the proposed method for the analysis of different degradation processes occurring in timber members, with a special attention on wood aging, weathering, biotic decay by fungi and waterlogging. Examples of spectra evaluation as well as limitation of proposed methods are presented. Case studies including classification of decay type, analysis of the weathering dynamic and characterization of waterlogged wooden samples are briefly illustrated. Practical application of spectroscopy within timber structure assessment is considered as a very important supplement to the typical information collected during ordinary tests. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The use of wood-based connectors as a possible substitute of metal fasteners, for specific applications, in modestly loaded and moderately dense timber components, in new timber assemblies as well as for restoration works, is discussed. The densification technique has been used to obtain a wood-based material with higher mechanical performance with respect to the natural wood. A dedicated research has been carried out to monitor the compression behaviour of the wooden nails. The progress of pushing force during insertion of the wooden nails into wood samples was analysed and served for insertion process control. 600 compression tests were carried out to evaluate the mechanical behaviour of densified wooden nails, obtained from four different hardwood species and with different densification ratios. Beech, densified at 0° ring angle, 60% densification ratio, was selected for the further experimental campaign on the joints. Ten push-out tests have been performed on timber-to-timber joints. Results in terms of rigidity, resistance and post-elastic behaviour are discussed. The observed variability (slip modulus CoV = 26.7%, maximum load CoV = 23.7%) is mainly dependent on the occurrence of geometric flaws during nail insertion. Ductility exhibited by a group of joints was given by nail embedding into the wood before failure as well as by the bending resistance of the nail. The choice of an optimized technology for wood densification and for nail insertion is considered as a key factor for the optimal employment of the novel connectors. [ABSTRACT FROM AUTHOR]

On site characterization of wood members is a very challenging task, after consideration of all the variables affecting the material used for the construction and the complexity of the structure itself. Current procedures are limited to few characterizations; in general based on visual inspection supported by the localized drilling resistance analysis and moisture content estimation. The goal of this work was to highlight the potential of the infrared spectroscopy as a tool capable of providing complementary information for the expert inspector assessing the timber structures. The paper presents several examples of successful application of mid and near infrared spectroscopy as used for prediction of physical and mechanical properties of wood. Requirements for implementation of mid and/or near infrared spectroscopy in routine assessment protocols are also provided. [ABSTRACT FROM AUTHOR]

The proper timber structure assessment is of great importance to assure safe service of buildings as well as to preserve cultural heritage objects for future generations. However, due to peculiar anatomic structure of wood, anisotropy and heterogeneity, its characterization is a problematic task. Several methods are used nowadays for improving existing structure assessment routines, including also continuous monitoring of the structure performance. Current trend for using multiple sensors simultaneously is more favorable than a single sensor approach due to superior representation of the real-world cases. Moreover, the availability of novel statistical tools to handle many variables concurrently is another motivation for rapid changes within the field of measurement technology. It is important, therefore, to assure proper pre-processing of the signals from sensors, appropriate data fusion and optimal data analysis. The integrated use of non-destructive testing methodologies and data handling techniques to assess, monitor and predict properties of wood within structures and buildings is briefly described in this work. Examples for successful applications of the different data analysis techniques on the assessment and monitoring of civil engineering constitutions are reported. Multi-sensor approach may be a very attractive alternative to the conventional assessment and can provide supplementary data to be considered when inspector decision is made. It is assumed that, after additional developments, such methodologies can serve as assisting tools for non-destructive assessment of the wooden structures, service life prediction of structural elements and to support selection of optimal conservation process. [ABSTRACT FROM AUTHOR]

The manuscript presents the application of NDT imaging techniques as complementary tools to be used during visual inspection. NDT imaging can be used to map inhomogeneity and to identify the areas at the highest risk for damage in timber structures. The paper highlights the potential of imaging techniques accepted and practiced for the assessment of timber structures. Multi-sensor approaches are presented and recommended for multi-scale, multi-resolution correlated information, which allow the non-destructive, reliable and fast assessment of damage and risk level in the existing timber structures. [ABSTRACT FROM AUTHOR]

The goal of this work was to understand and model the combined effect of time, geographical location, and exposure on the physical–chemical mechanisms of wood weathering in structures. Series of wooden samples were exposed to natural weathering in seven locations varying in climatic conditions, including Italy and north Germany. The set of samples was exposed for 4 years, collecting representative samples each year. Four exposure directions (north, south, east, and west) were investigated. Measurements of samples included: photogrammetry, near and mid infrared spectroscopy, color, gloss, roughness, and elemental composition (x-ray fluorescence spectroscopy). Results showed that the surface degradation mechanisms caused by weathering were affected by the site of exposure. The wood samples weathered in the Italian sites, in Udine and Macerata, were most degraded. The most significant changes were observed in samples exposed to the south direction. The original algorithm for calculation of “the weathering indicator”, by merging the multi-sensor data and linking these to the surface performance indicators was developed. Finally, the subjective visual assessment by the expert person was compared with parameters obtained by measuring the weathered surfaces with various sensors. A good correspondence between weathering indicator Windand subjective quality index was established. [ABSTRACT FROM PUBLISHER]

Since trees record all the environmental factors in the wood, many wood properties are related to the site characteristics. Despite of this fact, identifying the origin of a timber has always been considered a difficult task, and no effective tools are presently available for this purpose. The goal of this study was to verify whether significant differences among groups of the same wood species due to the provenance can be detected with Fourier transform near-infra-red spectroscopy (FT-NIR). Spruce ( Picea abies L. Karst.) samples collected from stands in Finland, Northern and Southern Poland and Italy were analyzed using two different approaches: for the first approach samples were collected from four provenances scattered in a wide area throughout Europe, while for the second approach the samples were collected from provenances located in a narrow area within the same region in Italy. For the first approach, all the specimens were clearly divided into groups by using statistical methods. The separation among groups from the narrow local area was actual; even though less significant than in the previous case. It was concluded that trees growing in various locations have somewhat different chemical composition, and FT-NIR is sensitive enough to detect such differences. The presented method could be used for tracking wood provenances and as a technical tool for detecting logs harvested illegally from protected areas. [ABSTRACT FROM AUTHOR]