Maria Pia Repetto

Dynamic alongwind fatigue of slender vertical structures

The wind-excited vibrations of structures induce fluctuating stresses around mean deformation states that lead to fatigue damage accumulation and can determine structural failure without exceeding design wind actions. This paper proposes a mathematical model aimed at deriving a histogram of the stress cycles, the accumulated damage and the fatigue life of slender vertical structures (e.g. towers, chimneys, poles and masts) in alongwind vibrations. The formulation, integrally in closed form, is based on a probabilistic counting cycle method inspired by narrow-band processes. An example illustrates the proposed procedure and shows, through the comparison with Monte Carlo simulations, the entity of the approximations involved by treating the response as narrow-banded instead of broad-banded.

A web-based GIS platform for the safe management and risk assessment of complex structural and infrastructural systems exposed to wind

Abstract This paper describes an extensive research activity, carried out at the University of Genova, aimed at developing an integrated web-based GIS platform for the safe management and risk assessment of complex port areas exposed to intense wind actions. This activity, carried out through the Projects “Wind and Ports” and “Wind, Ports and Sea”, financed by the European Territorial Cooperation Objective, Cross-border program “Italy–France Maritime 2007–2013”, includes the realization of a wide in situ monitoring network, specific numerical codes for the multi-scale simulation of wind and wave fields, wind and wave forecasting algorithms, and statistical wind climate analyses. All the results obtained are made directly available to the port operators through a web-based GIS platform integrated into a global system for the safe and operational management of the port areas involved in the above projects. In particular, the monitoring and forecasting systems work out operative results in continuous mode. The generality of the implemented platform makes it immediately suitable for applications to any port reality worldwide and, even more, to any complex structural and infrastructural system under wind actions.

General tendencies and classification of vertical structures under gust buffeting

Abstract The 3-D gust effect factor (GEF) technique is an efficient method to determine the maximum displacements and internal forces of vertical structures subjected to alongwind, crosswind and torsional gust-excited vibrations. All these effects and the related equivalent static forces may be evaluated through one non-dimensional quantity referred to as the 3-D GEF, whose expression was found in closed form. This property makes very attractive the use of functional analysis to establish general tendencies and classification strategies. Confirming some previous results limited to alongwind vibrations, this paper shows that such tendencies are mainly related to the shape of the fundamental modes of vibration. Structures are thus classified into homogeneous categories and general rules are provided to assess a priori the distribution of internal forces. Errors inherent the determination of internal forces by the classical gust response factor technique are also discussed. Among several aspects of engineering interest, those concerning wind actions on the foundation and the stress state for wind-induced fatigue deserve particular attention.

Closed-Form Prediction of the Alongwind-Induced Fatigue of Structures

AbstractWind-induced fatigue is a crucial topic in the design of wind-sensitive structures. Despite this, methods proposed in literature are mainly addressed to research, or they are too simplified for engineering applications. Thus, suitable engineering and standards procedures are almost totally lacking, which is a major shortcoming in structural and wind engineering. Starting from a closed-form solution (CFS) recently proposed by the authors, this paper develops a novel engineering approach to evaluate the alongwind-induced fatigue of structures and structural elements. This approach is based on a hierarchy of hypotheses that lead to a progressive simplification of the basic formulation. Two classes of formulas, referred to as Levels I and II CFSs, are obtained and critically discussed with special concern for input parameters. Level I CFS implies three further simplifications joined together by the common aim of providing refined approximations of the reference target solution. Level II CFS implies th...