Aeroelastic instability and wind-excited response of complex lighting poles and antenna masts Cung Huy Nguyen, Andrea Freda, Giovanni Solari, Federica Tubino ⇑ Department of Civil, Chemical and Environmental Engineering (DICCA), University of Genoa, Via Montallegro, 1, 16145 Genoa, Italy article info Article history: Received 21 February 2014 Revised 6 November 2014 Accepted 9 December 2014 Keywords: Aeroelastic instability Antenna mast Buffeting Lighting pole Vortex shedding Wind-excited response Wind tunnel tests abstract This paper presents analytical and experimental investigations aimed at evaluating the aeroelastic instability and wind-excited response of slender vertical cantilever structures, in particular complex lighting poles and antenna masts with distributed eccentricities. The application of the methods herein presented to a real structure emphasizes the significance of aerodynamic eccentricities, upper vibration modes and coupling between the translational components of the motion. In such a framework, partic- ular sets of the parameters and specific structural configurations may cause very low critical galloping velocities. Additionally, the hypothesis of polar symmetry commonly used in technical calculations may lead to relevant underestimations of the wind-excited response. From this point of view, this paper provides possible interpretations for a number of damage and collapses of this structural type without clear and suitable explanations. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Lighting poles and antenna masts may appear as simple struc- tures that can be modelled, very easily, by slender vertical cantile- ver beams with one or more concentrated masses usually at their top; these are often the concepts that inspire engineering calcula- tions. A deeper reflection on this structural type points out totally different characteristics. These structures are built in such a large and growing number as to represent a relevant economic problem in spite of low single cost. They are characterized by increasing height, lightness, slenderness and complicated shape (Fig. 1) that make them extremely sensitive to complex aeroelastic phenomena and wind-excited vibrations, such as to require refined analyses in order to capture their physical behaviour. An impressive number of damage and collapses that increasingly involved these structures, often due to wind-excited fatigue [1–6], but in many cases not so well understood, emphasizes their susceptibility to wind actions and their potentially dangerous role in the anthropogenic territory. A dominant property that joins engineering calculations and research investigations is the idealization of lighting poles and antenna masts as polar symmetric structures. This is not correct due to several peculiar features such as stairs, cable bundles and/ or solar panels, frequently applied to the shaft of these structures, lighting devices, top balcony, antennas and/or parabolas, often put eccentrically with respect to the axis of the shaft, and cylinder hulls, which ever more frequently cover the transmission devices being endowed with non-circular sections due to construction imperfections. One or the whole of these elements gives rise to mass and shape eccentricities, which make these structures com- plex both in mechanical and aerodynamic terms. Such an aspect greatly contributes to make lighting poles and antenna masts sen- sitive to potential instabilities caused by aeroelastic phenomena and exposed to intense and non-conventional wind-excited vibrations. In spite of a large number of investigations on slender vertical cantilever structures, e.g. [7] and [8], literature review shows that there are few theoretical and experimental studies concerning the role of eccentricities. Caracoglia and Jones [2] studied the galloping behaviour and the buffeting response of poles with a luminaire at the top; the effect of eccentric aerodynamic loads at the level of the luminaire was taken into account, but the pole shaft was consid- ered as polar symmetric. Chang et al. [3,4] investigated the vortex shedding and buffeting response of luminaire poles in which aero- dynamic parameters were determined by wind tunnel tests carried out on dodecagonal cross section. Solari and Pagnini [9] formulated the problems of the wind-excited response and galloping behav- iour of lighting poles and antenna masts with concentrated masses and different modes, without considering eccentricities. http://dx.doi.org/10.1016/j.engstruct.2014.12.015 0141-0296/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +39 010 353 2501. E-mail address: federica.tubino@unige.it (F. Tubino). Engineering Structures 85 (2015) 264–276 Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct