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Methodology for the analysis of complex historical wooden structures
Abstract
This paper deals with several items concerning the restoration of historical wooden structures. Firstly general problems related to the identification of the material and of the whole structural complex are faced. They are mainly influenced by either wood defects and degradations or past technologies for construction. An overview of the possible upgrading intervention is also introduced. Therefore the paper has been focused on a study case of historical roofing structure. In particular the detailed geometrical and mechanical surveys are presented. The main aspects of the structural modeling are evidenced and the results of the structural analysis are discussed. On the bases of the structural behavior pointed out, the appropriate retrofitting intervention has been illustrated.
... Wood is principally composed of cellulose microfibrils embedded in a matrix composed of lignin and hemicelluloses. The effect of fungi or/and weathering on wood cell wall components and the process involved have been clarified to a great extent (Mazzolani et al. 2005;Pedersen et al. 2015;Srebotnik and Messner 1991). Depending on the factors connected with the environment and atmosphere, wood cell wall components are degraded differently; oxidation, hydrolysation, depolymerization and other chemical processes (Blanchette 2000). ...
An important traditional load bearing member in oriental ancient timber structure buildings, i.e. Huagong (flower arm), was selected to explore the alterations in cell wall components and hygroscopic properties of wood during long time ageing. This archaeological poplar (Populus spp.) wood with cal. BP 690: BP 790 was studied from the wood surface and inwards by means of imaging FTIR spectroscopy, X-ray diffraction and dynamic vapour sorption. The deterioration of the archaeological wood mainly displayed a depolymerization of glucomannan and lignin as well as a hydrolysis of the glucuronic acid of xylan and of the aromatic C–O groups in the condensed lignins or lignin–carbohydrate complexes. Furthermore, the degradation promoted the rearrangement of the cellulose molecules in adjacent microfibrils. The cellulose crystallites in the archaeological wood were therefore packed more tightly and had larger diameter. The structural alterations of wood cell wall components and a decrease in crystallinity contributed to an increase in the number of moisture bonding sites and led to an increase in both the equilibrium moisture content of the archaeological wood in the entire RH range as well as an increase in hysteresis.
... El método del elemento finito encuentra su aplicación en la verificación de resultados experimentales y la validación de enfoques teóricos en los problemas de secado de madera, así como para resolver problemas de plasticidad, de fractura y de análisis no lineal de estructuras (Mackerle, 2005y COST Action FP0802, 2011. Estos argumentos han sido validados por Marzo (2006) y Magnus (2008, quienes evalúan la capacidad portante de estructuras de techos, empleando el método del elemento finito en estudios de caso de edificios históricos de madera. ...
Las tipologías arquitecturales encontradas en el contexto del análisis estructural de construcciones con significado histórico y cultural son complejas. El modelado numérico es propuesto como una solución para diagnosticar la seguridad estructural de estas edificaciones. En esta investigación se realizaron pruebas de flexión estática y se calcularon los módulos de elasticidad y de ruptura en vigas antiguas de P. abies. La densidad de la madera fue de 422 kg/m3 para las vigas con un contenido de humedad de 12 %. El módulo de elasticidad promedio fue de 9,059 MPa y el módulo de ruptura fue de 29.18 Pa. Los módulos presentaron una variabilidad aceptable. Los resultados experimentales se contrastaron con las predicciones numéricas empleando el método del elemento finito. Las predicciones numéricas en los dominios lineal y no lineal mostraron buena aproximación con los resultados experimentales.
... El método del elemento finito encuentra su aplicación en la verificación de resultados experimentales y la validación de enfoques teóricos en los problemas de secado de madera, así como para resolver problemas de plasticidad, de fractura y de análisis no lineal de estructuras (Mackerle, 2005y COST Action FP0802, 2011. Estos argumentos han sido validados por Marzo (2006) y Magnus (2008, quienes evalúan la capacidad portante de estructuras de techos, empleando el método del elemento finito en estudios de caso de edificios históricos de madera. ...
The architectural typologies found in the context of the structural analysis of constructions with historical and cultural meaning, are complex. Numeric modeling is proposed as a solution to diagnose the structural safety of the edifices. In this research, static bending tests were performed and the moduli of elasticity and of rupture corresponding to old beams of Picea abies wood were calculated. The wood density was of 422 kg/m3 for beams with a moisture content of 12 %. The average modulus of elasticity was of 9,059 MPa and the modulus of rupture was 29.176 MPa. The moduli of elasticity and of rupture of the beams presented an acceptable variability. The experimental results were contrasted with the nu-meric predictions employed by the finite element method. The numeric prediction in the linear and nonlinear domains showed a good approximation with the experimental results.
... They present a study case where they contrast experimental results with numerical predictions. Marzo (2006) implemented a 3D finite element model to analyze a historical wooden structure case study. The author recommends that the numerical simulation should be strongly related and adapted to the particularities of the ancient wooden structural elements. ...
... Relativamente à capacidade resistente da madeira reutilizada, Marzo (2006) indica que os elementos de madeira antiga analisados apresentam geralmente diminuição do módulo de elasticidade em cerca de 25%, resultante de vários fatores, tal como envelhecimento do material, excentricidades resultantes de fraca execução, ligações deficientes, entre outros. Por sua vez, Pilt et al. (2009) consideraram a ocorrência de diminuição da capacidade resistente da madeira antiga de cerca de 15%. ...
In Portugal, the house building industry has mostly adopted reinforced concrete framed structures and clay brick-wall. The use of other structural materials, such as steel, timber, and stone-wall is still rather limited in this sector. Moreover, the use of earth-based construction techniques and solutions still remains limited to individual cases. Within this context, this paper describes an investigation on sustainable structural solutions for a typical single family house using natural materials. Three different structural solutions were compared, namely a reinforced concrete frame solution, a solution based on CEB (compressed raw earth blocks) masonry and timber structures for floors and roof, and a solution based on reusable materials, such as timber originated from the demolition of buildings. These alternative structural solutions were compared in terms of building costs, energy consumption and CO2 emissions. The study confirmed that the sustainable solutions had most advantages, particularly with regards to the environment.
... Pine wood is of course a species that has been extensively analysed following several years of direct exposure to weathering. In the same context, Marzo [2006] concluded that ancient timber elements may have their original modulus of elasticity decreased by approximately 25% and as a result of several factors, such as: material aging, poor construction labour, weak connections, among others. Meanwhile, Pilt et al. [2009] concluded that the ancient timber may have its strength capacity decreased by approximately 15%. ...
... As principais manifestações patológicas estruturais comummente identificadas nestes elementos são a existência de grandes fissuras, a existência de nós e o apodrecimento dos extremos dos elementos (zonas de apoio). Relativamente à capacidade resistente da madeira reutilizada: os elementos de madeira antiga analisados no seu estudo apresentaram geralmente uma diminuição do módulo de elasticidade em cerca de 25%, resultante de vários factores, tal como envelhecimento do material, excentricidades resultantes de fraca execução, ligações deficientes, entre outros (Marzo, 2006 ...
... In particular, for the design of connectors, reference is made to a composite wood-steel-concrete beam floor to be realised for the structural restoration of an ancient historical timber floor [5,8,9]. The design values of the shear force to be transferred (F 0 ) and the required stiffness (K 0 ) are 24 kN and 55 N/mm 2 , respectively. ...
This paper deals with the study of an innovative reversible type of connection system for a composite timber beam-concrete slab floor purposely conceived for the application to ancient timber floors. Refined numerical models of different configurations of such a connection system are set-up through the nonlinear code ABAQUS in order to evaluate their performances by means of push-out analyses. The comparison among solutions in terms of strength and stiffness has provided useful indications for the optimization of the system in terms of both geometrical and mechanical characteristics, as well as for its use as reversible intervention for seismic retrofitting purposes.
Salix psammophila has been extensively used as a sand barrier material for various desertification control applications over the years. Thus, elucidating the long-term degradation processes of this sand barrier in desert environments is of great importance. In this study, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and chemometric methods were used to evaluate and compare the structure and performance of the S. psammophila sand barrier during degradation. The results clearly showed that the structure and performance of the S. psammophila sand barrier varied in the different vertical sections of the barrier. With the increase in the setting period of the sand barriers, the atmospheric exposure section (AES) and stable sand buried section (SSBS) exhibited deterioration and decay, respectively. The mass loss rate was SSBS>AES>ASDI, which also exhibited different degrees of decrease in mechanical properties such as in the modulus of rupture, ultimately resulting in lodging, damage, and the loss of the function of the S. psammophila sand barrier in preventing wind-sand movement and fixing quicksand. Microstructural changes showed that after eight years of setting, the vessel and parenchyma cells were severely damaged and the corresponding chemical components, such as cellulose, hemicellulose, and lignin, were degraded to a certain extent. The decrease in the crystallinity index values based on the XRD analysis confirmed the deterioration and obvious changes in the crystallinity, which affected the strength of the S. psammophila sand barrier. The FT-IR analysis indicated that several characteristic peaks of cellulose, hemicellulose, and lignin in the AES and SSBS sections disappeared or were weakened compared with the ASDI section. Comprehensive analysis showed that the primary reason for the serious deterioration in AES was the aging caused by exposure to continuous UV radiation in the atmospheric environment, while the serious decay of SSBS was mainly caused by microbial and fungal activity in the sandy environment, ultimately leading to the degradation of the S. psammophila sand barrier. Our findings suggest that it is necessary to further strengthen the anti-aging and anti-corrosion measures in the resource utilization process of the S. psammophila sand barrier in the future.
Historic buildings composed of timber vaults with planked arches are an important part of European and Latin-American heritage. However, research on the structural assessment of timber planked arches has so far assumed the arches as continuous. In this paper, the nailed joints of the arches are realistically modelled using springs of finite stiffness and the importance of their simulation to the whole structural response of the vaults is discussed. The approach is used to simulate the three-dimensional seismic behaviour of the timber vault of the Cathedral of Ica, which was severely damaged by the 2007 Pisco earthquake. The numerical results and analytical models currently available in Eurocode 5 are used to explain the failure of the nailed joints of the arches of the cathedral in shear parallel to the grain and tension perpendicular to the grain . An assessment procedure of timber planked vaults by means of numerical modelling, from input parameters’ validation to diagnosis, is presented with a relevant and complex case study, which can be applied to other similar constructions.
The paper deals with the study of the ancient timber structures of the Royal Palace of Naples. The attention is focused on the complex covering of the Guard Room (XXIX) of the Historical Apartment. Firstly, geometrical and mechanical in situ surveys are presented. Then, the capacity of the structure in terms of deformation and resistance is evaluated through numerical analyses on purposely set up 3D FEM models.
Timber joints are usually considered as perfectly pinned or stiff against rotation during the calculations of engineering timber structures. However the semi-rigid behavior the joints cannot be avoided in case of accurate calculations. In this paper the rotational stiffness and the full moment-rotational behavior of dowel-type timber joints were analyzed using computer algorithm validated by finite element analysis. Based on the numerical calculation and the experimental results the paper describes the influences of the joint geometry, the grain direction and the number and position of connectors on the moment-rotational behavior.
Instead of high value willow-poplar galleries and ash-oak-elm galleries stands of non-indigenous species are present at many sites of the flood plain of Danube in the Béda-Karapancsa Region of the Danube Drava National Park. According to the Act of Nature Conservation in Hungary minders of the territories are obligated to change non-indigenous tree species to natural tree species in all forest stands (e.g. monocultures), that are on protected areas. Change of forest structure has to be determined by the recent type of stand, the future stand and the site; its speed is fitted to the whole territory. The affects of water regulation works on the area must be taken in regard. It is necessary to monitor the results of the changes of forest structure by indicators of naturalness. It can be done by the method of naturalness value of forest stands (TERMERD).
Modeling timber joints it is essential to know the stiffness of the connections. In some cases the prescriptions of the standards contain only general approach without considering significant effects. The presented paper analyzes the load-slip behavior of dowel-type timber joints. A computer calculation method is presented, which is able to take into account the geometrical and stiffness parameters as well as the different joint arrangements.
Before the 1960s the ductility notion was used only for characterizing the material behaviour. After Baker's research on plastic design, this concept has been extended to the structural level. This paper provides a general overview of ductility. The paper examines the behaviour of material ductility, cross−section ductility and member ductility separately, then it studies how the sum of the effects of all these ductilities affect the structural ductility. The effect of the different ductilities can be built into the structural behaviour through an interactive hinge model. The model of the interactive hinge also takes into consideration the effects of the residual stresses and deformations, the strain hardening and the plate buckling.
Em Portugal, a indústria de construção habitacional tem recorrido essencialmente às estruturas de betão armado e de alvenaria de tijolo cerâmico. As estruturas metálicas, de madeira e de alvenaria de pedra têm tido expressão reduzida nesse setor da construção, e são muito pontuais as aplicações da terra crua como solução construtiva. Nesse contexto, pretende-se estudar soluções construtivas mais sustentáveis, recorrendo a materiais de construção naturais. Para o efeito, foram estudadas para uma habitação unifamiliar com tipologia típica três soluções estruturais: estrutura porticada de betão armado e lajes aligeiradas pré-fabricadas; solução estrutural à base de materiais naturais; e solução que contempla a reutilização de madeira proveniente de demolições habitacionais. As soluções estruturais com recurso a materiais naturais estudadas são definidas por paredes resistentes de bloco de terra comprimida (BTC) e estrutura de madeira nos pavimentos e cobertura. Essas soluções estruturais são comparadas em termos de custo, gastos energéticos e teor de emissão de CO2 associados à construção. Verificou-se que as soluções mais sustentáveis são muito mais vantajosas no que diz respeito a esses três aspectos.
TTABSTRACT: The paper deals with the ancient timber structures of the Royal Palace of Naples (1600), which represent unique study cases of complex timber roofs and beam floors. The structural identification of some of them, in particular the roofing structures of the Royal apartments, has been achieved through the following subsequent levels of investigation: 1) in situ surveys, for getting both geometrical and mechanical features, through visual inspection combined with Non Destructive techniques, aimed at detecting defects and degradations; 2) FEM analyses on approximated structural models, for providing the stress distribution and deformation state of members, thus evidencing the critical parts of the structures and the residual strength. The selection and design of appropriate retrofitting interventions, where necessary, have been enabled by the acquired deepen knowledge of the timber structural systems.
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