Long term persistence in daily wind speed series using fractal dimension

In the assessment of wind turbines installations efficiency long series of wind speed data are necessary. Such data are not usually available it is then important to generate them. In this paper we examine the long-term persistence of daily wind speed data with many years of record using the fractal dimension. The persistence measures the correlation between adjacent values within the time series. Values of a time series can affect other values in the time series that are not only nearby in time but also far away in time. For this purpose, a new method to measure the fractal dimension of temporal discrete signals is presented. The fractal dimension is then used as criterion in an approach we have elaborated to detect the long term correlation in wind speed series. The results show that daily wind speed are anti-persistent

Optimization of design for floors, roofs and vaults

Typical horizontal elements in historic buildings are represented by timber floors and roofs and masonry vaults. All these components have a crucial role in seismic area, as they are required to resist under lateral loads, to improve the global behaviour through effective connections and to distribute forces, with proper in-plane stiffness, to the shear walls. Niker project, by the Work Package 5 (WP5) “Optimization of design for floors, roofs and vaults”, gave the opportunity to compare various strengthening solutions applied to representative components present in existing buildings, taking into account the variety of types on a regional scale, and considering as priority the selection and use of compatible techniques and materials and/or minimum interventions. These solutions are intended to preserve the existing horizontal elements by improving their mechanical performance, as needed to keep their structural contribution on the overall behaviour, thus avoiding generalized substitutions. The validation of strengthening techniques applicable to existing buildings was carried out by means of comprehensive laboratory experimental campaigns, the results of which were used to calibrate numerical models. Materials characterization and on-site investigations provided additional data to increase knowledge and calibrate models. On the basis of these results, parametric studies were performed, to support the design and assessment of strengthening components. In the paper, the main results obtained on strengthened horizontal components are described