This paper describes the preliminary results of an ongoing research activity involving Maritime Pine Cross-Laminated Timber (CLT) panels, aimed to exploit the potentialities of this native species of Sardinia. The modulus of elasticity (MOE) is a key parameter for grading wooden products and evaluating the overall mechanical properties of panels. Free Vibration tests can be an effective method to assess the dynamic MOE of wooden products; the method is based on the direct measurement of the first vibration mode frequency of the specimens and the indirect determination of the elastic parameters. The present work shows a straightforward approach to evaluate the dynamic MOE of cross-laminated panels by choosing suitable boundary conditions depending on the specimen sizes. For this purpose, various experimental tests were conducted on different configurations aiming to evaluate the dynamic MOE for the considered cases. Furthermore, the relationship between global vibrational behaviour of panels and original boards MOE has been investigated. The dynamic MOE obtained by vibration testing method has been compared with the static MOE evaluated by bending tests in order to find a correlation. A linear relationship between dynamic and static MOE was found, with the dynamic MOE being slightly higher than the static MOE, as expected. The dependence of the correlation upon the applied methodology was determined and regression equations were derived and are provided in the paper.
Vol. 17, n° 2, pp. [105][106][107][108][109][110][111][112][113][114] 2018 Revista UIS Ingenierías AbstractIn this project, a historic masonry building in Sardinia, Italy has been considered as a case study for the comparison of two approaches for modeling, static and seismic analysis. Two software with different modeling approaches were employed with the purpose of comparing and discussing the results. SismiCad12 was used to simulate the structural behavior of the historic masonry building. SismiCad12 uses the Finite Element Method (FEM) that allows to model and analyze most types of 3D structures, and it is suitable for masonry structures. On the other hand, a different and innovative modeling approach called Frame Macro Elements (FME) was also applied using the 3Muri software, specially designed for assessing the linear, nonlinear, and seismic behavior of masonry structures.Assuming the same hypothesis to construct the 3D model of the structure in each code, the results of the static analysis show a different distribution of the vertical loads in the structure, which are more realistic in the FEM modeling. This different criterion of evaluation of the vertical loads carries a mechanism of "soft floor" in the pushover analysis in the FEM modeling, and therefore, a lower ultimate displacement corresponding to the collapse of the structure. On the other hand, in dynamic analyzes, FME modeling is more receptive to reality, involving a massive percentage of masses participating in the first vibration modes.Keywords: macro-elements; historic structures; pushover analysis. ResumenEn este proyecto se ha considerado como caso de estudio un edificio histórico de mampostería en Cerdeña, Italia, cuyo modelado, análisis estático y sísmico han sido desarrollados. En este estudio se han empleado dos programas informáticos con distintos enfoques de modelización con el propósito de comparar y discutir los resultados. Como primer simulador del comportamiento de la estructura en mampostería se ha elegido SismiCad12, que es una suite de Elementos Finitos (FEM, por sus siglas en inglés) que permite modelar y analizar la mayoría de los tipos de estructuras 3D y es adecuado para estructuras de mampostería. Por otro lado, se ha aplicado un método de modelado diferente e innovador denominado Frame Macro Elements (FME) con el software 3Muri, diseñado específicamente para evaluar el comportamiento lineal, no lineal y sísmico de las estructuras en mampostería.Suponiendo la misma hipótesis para construir el modelo 3D de la estructura en cada código, los resultados de los análisis estáticos muestran una diferente repartición de las cargas verticales en la estructura, las que son más realísticas en el modelado FEM. Este diferente criterio de evaluación de las cargas verticales lleva un mecanismo de "piso suave" 106M. Saba, D. Meloni en el análisis de pushover en el modelado FEM, y por lo tanto un desplazamiento ultimo inferior correspondiente al colapso de la estructura. Por lo contrario, en los análisis dinámicos el modelado FME es má...
In the case of old existing structures where the cultural value is very high, structural health analyses and investigations would be better performed without damages or service interruptions. Thus, modal analysis aimed at identifying eigenfrequencies and eigenmodes represents a very effective strategy to identify structural characteristics. In this paper, an innovative strategy to identify structural parameters exploiting the modal information obtained from operational modal analysis is proposed. The importance of the structural modeling in the problem formulation is highlighted. In the case of a simply supported beam, it was possible to assess the beam steel elastic modulus, while in the case of a cantilever beam, some constraint characteristics have been evaluated as well. In the steel frame case, the focus was on the constraint conditions of the structure determining the flexural stiffness of the springs representing the column base constraints. The method performances are promising for applications in larger structures such as bridges and buildings.
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