Giuseppe Piccardo

Probabilistic 3-D turbulence modeling for gust buffeting of structures

Literature on turbulence modeling is rich in empirical, semi-empirical and theoretical spectral equations whose parameters assume deterministic values. Starting from a critical review of the state of the art, this paper proposes a unified model of atmospheric turbulence especially suited to determine the 3-D gust-excited response of structures. Unlike classical models, all parameters are assigned through first and second order statistical moments derived from a wide set of selected experimental measurements. A general discussion is also provided about model errors and other sources of randomness. Due to these properties the model proposed is suitable for carrying out reliability analyses which take into account the propagation of the uncertainties.

A complete dynamic approach to the Generalized Beam Theory cross-section analysis including extension and shear modes

A simple and efficient ‘complete dynamic approach’ is proposed, and named GBT-D, to evaluate a suitable basis of modes for the elastic analysis of thin-walled members in the framework of Generalized Beam Theory (GBT). The basis includes conventional and non-conventional modes, the latter accounting for transverse extension and membrane shear strain of the plate elements forming the cross-section, which identically vanish in the former set. The method relies on the solution of two distinct eigenvalue problems, governing the in-plane and the out-of-plane free oscillations of a segment of a thin-walled beam. Both the eigenvalue problems, differential in origin, and defined on a one-dimensional spatial domain, are transformed into an algebraic problem by means of a discretization carried out at the cross-section middle line. Numerical examples are then presented to outline the ease of use of the proposed method considering a single plate, an open cross-section and a partially closed one. Member analyses are also performed for the simplest boundary conditions, to validate the accuracy of the proposed GBT-D approach against finite element method results and analytical solutions, highlighting the importance in including the non-conventional modes.

3-D gust effect factor for slender vertical structures

Original studies on gust factor buffeting dealt with the alongwind displacement of structures. Research on this topic carried out since the nineties followed two distinct lines: the first determines the maximum effects due to the alongwind response; the second extends the original method from the alongwind response to crosswind and torsional responses. This paper represents the junction point of these research lines with reference to cantilever slender vertical structures. It derives the most relevant effects associated with the three-dimensional (3-D) wind-excited response of this structural type and shows that a suitable definition of one non-dimensional quantity, referred to as the 3-D gust effect factor, provides such effects at any level through a wide set of experimental, numerical and analytical procedures. A new definition of a 3-D equivalent static force consistent with this method is also introduced and critically compared with previous analogous statements.

A Continuous Approach to the Aeroelastic Stability of Suspended Cables in 1 : 2 Internal Resonance

This paper proposes a continuous perturbation treatment of the nonlinear equations of a cable, which is characterized by possible aeroelastic instability and internal resonance conditions. The objective is to evaluate the influence of stable modes (called passive) usually ignored when discretizing the model. The first step concerns the description of the structural equilibrium path under the action of the mean wind forces. Then, a multiple scale perturbation analysis of the integro-differential equations of motion is performed. Analyzing the stability of the reduced system, the existence of some limit cycles and of successive bifurcations is investigated. The comparison with previous papers, developed in the discrete field, allows clarification of the actual influence of the static equilibrium path and the contribution of passive modes.

Closed form prediction of 3-D wind-excited response of slender structures

Abstract This paper provides a concise, logical and operative scheme of a general procedure aimed at evaluating the alongwind, crosswind and torsional response of slender structures and structural elements. It also illustrates its application to the calculation of the 3-D wind-excited response of structures previously subjected to wind tunnel tests and full-scale measurements. The comparison between analytical and experimental results highlights the reliability of the procedure discussed herein.

A numerical algorithm for the aerodynamic identification of structures

High-frequency force balance wind tunnel tests involve the problem of determining the actual behaviour of the full-scale structure starting from the measured reactions at the base of its model. The literature is rich in approximate methods to derive the fundamental components of the modal wind actions. This paper proposes an alternative procedure to identify the Lagrangian components of the aerodynamic forces by a numerical algorithm.

A methodology for the study of coupled aeroelastic phenomena

Abstract A global model is identified inclusive of any whatsoever aeroelastic phenomenon, the linearization of which allows study of incipient aerodynamic instability through a solution methodology falling within the domain of the poles. With the variation of the mean stream velocity, study is made of the systems critical points and the form of the incipient instability represented by the same. Two structural examples are provided of the application of the methodology outlined.

A refined model for calculating 3-D equivalent static wind forces on structures

This paper describes the progress made in a research aimed at generalizing the gust factor technique from the sector of the alongwind response towards the 3-D wind response of structures. A unitary framework is given to the alongwind, crosswind and torsional vibrations of slender flexible cylinders. General expressions, based on a refined definition of the 3-D gust response factor, are derived for calculating the equivalent static wind forces. The possibility of solving the problem in closed form and the prospective of extending this formulation to three-dimensional bodies are also discussed.

Statistical analysis of high return period wind speeds

Abstract This paper demonstrates that in the range of high return periods different extreme wind speed distributions tend to agree or to diverge due to the parameters of the parent distribution. General criteria are therefore established to select a priori the most reliable or prudential model. Approximate relationships are also derived, for evaluating the parameters of a given model assuming as known the parameters of another.

Statistical analysis of extreme wind speeds in the Straits of Messina

Abstract This paper illustrates the methods for the statistical analysis of extreme wind speeds, drawn up on the occasion of the preliminary design for the construction of a bridge over the Straits of Messina. The studies are based on two alternative approaches, each one constituting a verification and control element for the other, leading to sound and generally reliable assessments. With the possibility existing for further improvement, the actual quality of the results obtained suggests that the procedures established could be applied to any situation.