229 research outputs found
Forze sociali e globalizzazione. Lo scontro sulle multinazionali nei lunghi anni settanta
No full text
Grandi Speranze. L'ONU negli anni Settanta
No full textDelinea le vicende dell'ONU negli anni Settanta: il segretariato di K. Waldheim; il declino del peacekeeping; l'ascesa del Terzo Mondo; le nuove tematiche: ambiente e diritti delle donne
Effects of Modelling Parameter Uncertainty on the Structural Response of Offshore Wind Turbines
No full textThe design of complex structures like Offshore Wind Turbines (OWTs) is commonly based on the results of deterministic structural analyses, carried out on finite element models of the structural system. However, the assessment of the structural response is affected by significant uncertainties, due to the random variability of both the environmental actions and the geometric and mechanical properties of the structure. An efficient procedure to deal with the uncertainty of modeling and loading parameters requires the characterization of the probability distribution functions of the parameters of the models of the actions and structural response, and the assessment of the probability distributions of the response parameters. Neglecting pertinent sources of uncertainty can lead to an incorrect evaluation of the stochastic structural response, and to an improper risk assessment. This paper focuses on the effects on the structural response of an OWT induced by the uncertainty of the parameters used to describe the environmental actions and the finite element model of the structure (referred to as the modeling parameters). A proper probability characterization of the parameters is assumed, and the relevance and the propagation of the uncertainty to the response are investigated. Reference is made to an OWT with a jacket support structure. Analyses are carried out in frequency domain by adopting a linear elastic finite element model, and the response uncertainty is estimated by using a sampling technique. The results presented in this paper are considered useful for the preliminary design phase, where upper and lower bounds of the stochastic structural response have to be estimated in order to select the design configuration. © 2010 ASCE
Structural Offshore Wind Turbines Optimization
No full textOffshore Wind Turbine (OWT) requires demanding and costly support structures. The conception, the design and the assessment of this kind of construction must consider several interacting and controversial aspects: there is a harsh design environment, relatively wide spectrum functional requirements, and exceptional scenarios. In fact, different aspects and various performances under several load conditions have to be investigated for this type of structures. This paper shows an optimization process related to the preliminary design of support structures for an OWT farm projected in the Mediterranean Sea showing the decision criteria considered. A strutted scheme is introduced and optimized with main reference to Ultimate Limit States (ULS) to obtain a baseline design. © 2010 ASCE
Performance-based design of structures under Aeolian Hazard
No full textIn this study, a probabilistic procedure for the performance-based design of tall buildings subject to wind actions is illustrated and applied to an example case: the assessment of the occupant comfort requirement for a 74 storey building. The occupant comfort is related to the perception of building vibrations under wind actions. The central objective of the procedure is the assessment of the adequacy of the structure through the probabilistic description of a set of Decision Variables (DVs): a DV is a measurable attribute that represents a specific structural performance. In the example case, DV is the peak value of the across-wind acceleration at the top of the building, and the risk is conventionally expressed by the probability that DV exceeds proper threshold values, defined as a function of the fundamental period of vibration of the structure. © 2011 Taylor & Francis Group, London
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