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Free-standing lattice towers are structures used for various purposes such as radio and television broadcasting, electric power and microwave transmission, meteorological measurements, wind energy production and so on. Due to their properties, they are mainly sensitive to wind loads. A longstanding discussion on the wind loading effects on this structural type has been carried out in the literature. This paper investigates the alongwind load effects on free-standing lattice towers by introducing specific influence functions of displacements, shear forces, bending moments and axial forces in leg elements. Such influence functions are first derived, calibrated and validated for the most typical structural types, then they are used within the framework of the gust effect factor technique. Comparative studies with reference to both the traditional use of cantilever beam approaches and finite element methods point out the role of the bracing pattern and, more precisely, of the level of the crossing of diagonals in tower panels. All the applications developed here refer to real structures with different properties. Results are interpreted and compared with those provided by previous studies on this structural type. Engineering and design issues are discussed focusing on the most critical aspects concerning dynamic wind loads. [ABSTRACT FROM AUTHOR]

Abstract: This paper analyzes the fatigue collapse of two slender structures due to wind-induced vibrations. The analysis is based on a complete procedure for the wind-induced fatigue analysis proposed by the authors. The application of the proposed method, compared with the real cases examined, leads to accurate fatigue life prediction; moreover, it gives a complete picture of the stress state and damage of the structures, furnishing useful information on the structural behavior and a key for the interpretation of collapses and damage causes. In particular, the analysis highlights the critical aspects of the aerodynamic behavior of the considered structures and suggests some remarks on the current state-of-the art on design against wind-induced actions. [ABSTRACT FROM AUTHOR]

Abstract: Wind-induced fatigue is a crucial topic in the design of several structural types. Despite this, the methods proposed in the literature have been developed mainly for research purposes. As a consequence, reliable engineering and standard methods for wind-induced fatigue analyses are still very limited and mainly addressed to the crosswind-induced fatigue caused by vortex shedding. Based on these considerations, this paper proposes a novel approach to evaluate the alongwind-induced fatigue of slender structures and structural elements. Starting from the procedure recently proposed by the authors, a hierarchy of hypotheses is introduced and critically discussed, which leads to a progressive simplification of the basic formulation. Two levels of formulae are derived, namely a closed form solution and an approximated closed form expression of the wind-induced damage; these represent a solid base from which to derive suitable methods for engineering calculations and standards. Application of the proposed solutions shows good agreement with numerical results. [Copyright &y& Elsevier]

Since the pioneering studies developed by Alan G. Davenport, the equivalent static actions on structures are a key topic of the wind engineering research. Two main methods have been proposed. The former, referred to as the gust factor (GF) technique, defines wind actions through a unique load distribution scaled by a non-dimensional coefficient eventually depending on the effect considered. The latter, referred to as the load combination (LC) technique, defines wind actions, till now in the alongwind direction, as a combination of three distinct load distributions associated with the static, quasi-static and resonant parts of the response. This paper provides a rational scheme and a generalisation of these procedures with reference to cantilever vertical structures. As for the GF technique, also the LC technique is initially extended to the 3-D response, discussing critically a set of alternative models for the quasi-static part of the loading. A new method is also proposed, referred to as the global loading technique, where equivalent static wind actions are assigned as a unique load distribution independent of the load effect considered. All problems dealt with in this paper are solved in closed form. [Copyright &y& Elsevier]

This paper illustrates and discusses the progress and the prospects of analytical methods for estimating the wind-induced response of structures, with special regard to cantilever vertical structures. Also in this era of large facilities and super-computers, closed form solutions, eventually assisted by user-friendly numerical programs, electronic sheets and symbolic calculus tools, imply relevant significance and great potentialities. Their use may be divided into two operative lines, referred to as direct applications and integrated procedures. Direct applications concern those analyses that pursue their aims by applying analytical methods autonomously; they comprehend two broad classes of procedures addressed, respectively, to solve specific engineering problems and to assess general tendencies. Integrated procedures concern those analyses that pursue their aims through articulated flow-charts whose logical blocks imply analytical methods, numerical algorithms and experimental measurements; embedded in such a context, analytical methods are powerful tools to establish reliable procedures for the aerodynamic identification of structures and to solve complex wind engineering problems, among which the propagation of uncertainties, structural reliability and wind-induced fatigue, otherwise almost prohibitive. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]