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Thunderstorms winds are localized and transient phenomena characterized by three-dimensional non-stationary velocity fields. While numerous studies investigated the wind loading on cantilevered structures under thunderstorm downburst winds, there is a lack of fundamental research on the behavior of simple circular cylinders subjected to downburst-like outflows. This paper investigates the pressure distribution and aerodynamic coefficients of two cylinders with different diameters immersed in three different types of wind: (1) isolated downburst (DB); (2) downburst embedded in an atmospheric boundary layer (ABL) wind (DBABL); and (3) steady ABL wind. The focus of this study is to provide a comparative analysis between aerodynamic coefficients (drag and lift) and surface pressures that result from these three different wind systems. The ABL winds caused a higher drag on the thinner cylinder than the two DB-like outflows. The lift coefficients during the primary vortex passage in the DB-like outflows were negative at the base of the cylinders and approached zero or to slightly positive values close to the cylinders' top. The location of the cylinders in DB-like outflows is the dominant factor for their aerodynamics. [ABSTRACT FROM AUTHOR]

Summary: A number of river bridges collapse worldwide every year during flood events, due to combination of actions including traffic loads, water and wind load, riverbed degradation, and accumulation of debris. Incidence of failure is higher for relatively old bridges that may have been designed without adequate consideration for some of such actions, in particular the scour potential at piers and abutments; in this case, consolidation of bridge foundations may be required. As an alternative to structural rehabilitation, we propose here real‐time management as a nonstructural risk‐mitigation measure: Data from a monitoring system aid the bridge managers to decide whether a bridge should be partially or totally closed to traffic in the case that forecasted environmental conditions indicate that the structure may exit its safe operational domain. A peculiar feature of the present proposal is that the monitoring system focuses on the evaluation of the environmental actions on the structure rather than on the health state of the structure itself: Such choice allows sufficient lead time for bridge closure. Bridge management may not prevent the damage of the structure but should avoid casualties. The methodology is presented with reference to the field case of a bridge over the river Po (Italy); its generalization to a larger variety of conditions is also discussed. [ABSTRACT FROM AUTHOR]

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]

Starting from an overview on the research on thunderstorms in the last forty years, this paper provides a general discussion on some emerging issues and new frameworks for wind loading on structures in mixed climates. Omitting for sake of simplicity tropical cyclones and tornadoes, three main aspects are pointed out. The first concerns the separation and classification of different intense wind events into extra-tropical depressions, thunderstorms and gust fronts, with the aim of improving the interpretation of the phenomena of engineering interest, the probabilistic analysis of the maximum wind velocity, the determination of the wind-induced response and the safety format for structures. The second deals with the use of the response spectrum technique, not only as a potentially efficient tool for calculating the structural response to thunderstorms, but also as a mean for revisiting the whole wind-excited response in a more general and comprehensive framework. The third involves the statistical analysis of extreme wind velocities in mixed climates, pointing out some shortcomings of the approaches currently used for evaluating wind loading on structures and depicting a new scenario for a more rational scheme aiming to pursue structural safety. The paper is set in the spirit of mostly simplified analyses and mainly qualitative remarks, in order to capture the conceptual aspects of the problems dealt with and put on the table ideas open to discussion and further developments. [ABSTRACT FROM AUTHOR]

The wind-excited vibrations of structures induce fluctuating stresses that lead to fatigue damage accumulation and may determine structural failure without exceeding ultimate strength. This paper proposes a mathematical model aimed at deriving the histogram of the stress cycles, the accumulated damage, and the fatigue life of slender vertical structures exposed to simultaneous alongwind and crosswind vibrations. Wind climate is modeled by the joint density function of the mean wind velocity and direction. Wind-induced actions consist of aerodynamic forces on the stationary structure and of aeroelastic forces due to the structural motion. Aerodynamic actions on the stationary structure are caused by the turbulence of the oncoming flow, dealt with through quasisteady theory, and by the vortex wake, considered as independent from turbulence. Aeroelastic forces are aimed at reproducing the lock-in phenomenon. The static and the quasistatic parts of the structural response are evaluated by the influence function technique, taking all modes of vibrations into consideration. The resonant part of the response is related to the fundamental alongwind and crosswind modes only. The probabilistic accumulation of damage due to aerodynamic actions on stationary structures is estimated by a counting cycle method inspired by narrow band processes. The damage in lock-in conditions is superimposed by counting stress cycles deterministically. The examples illustrate the application and the effectiveness of the proposed procedure, focusing attention on the role of upper modes and wind directionality. [ABSTRACT FROM AUTHOR]

Presents the results of an analysis of Proper Orthogonal Decomposition (POD) applied to the wind loading of a stationary and vibrating bridge deck box section by means of wind tunnel tests. Background on POD; Use of the method Covariance Proper Transformation or Spectral Proper Transformation to investigate the characteristics of the wind induced excitation; Explanation on the different excitation mechanisms detected at different wind speeds.

Focuses on the integrated procedures in wind engineering. Background on the growth of procedures and methods in the field of wind engineering; Proposal for a general scheme of the basic concepts for estimating the reliability of structures under wind loads; Discussion on modern algorithmic tools aimed at making the reliability analysis conceptually correct and operatively possible.

Wind actions are crucial for the safety and sustainability of structures. The wind climate of Europe and many other parts of the world is dominated by synoptic extra-tropical cyclones and mesoscale thunderstorms. Thunderstorms are frequent events that cause wind speeds and damage often greater than those of cyclones. This paper describes a wide research activity including an extensive monitoring network, an unprecedented database of transient wind speed recordings, a broad spectrum of numerical tools for elaborating data and extracting their statistical properties relevant to the wind loading of structures, the development of wind tunnel tests and CFD simulations, investigations on weather scenarios and damage surveys aiming to complete the information provided by field measurements. Based on these resources, a new generation of wind loading models is being developed – response spectrum technique, time-domain integration, evolutionary spectral density - robustly coherent with measured data and intrinsically coherent with each other. These studies are being carried out in the framework of the project THUNDERR, funded by the European Research Council (ERC) with an Advanced Grant 2016 in order to produce outcomes physically correct, transferable to design and standards, suitable to modify the current wind loading format and make constructions wind-safer and cost-efficient. • THUNDERR project studies thunderstorm outflows and their impact on structures. • Outflows are studied by real measurements, CFD simulations and wind tunnel tests. • New wind loading models are being developed to account for thunderstorm effects. • Design practices will benefit of THUNDERR outcomes to make constructions wind-safer. [ABSTRACT FROM AUTHOR]

With the development of mountain areas, more wind-sensitive infrastructures are constructed. In the design of these infrastructures, the wind loading cannot be accurately obtained from the code based on the flat area. Hence, it is of great importance to study the mountain wind characteristics. In this study, the wind field measurement was initiated in a mountain area of western China. After the examination of the measured data, two typical wind events including the thunderstorm wind and thermally developed wind are highlighted. To extract and separate these wind events, an automatic classification method is proposed. The thunderstorm wind is analyzed in order to capture the rapid variation of its maximum wind speed, mean temperature and mean humidity through the boxplot method while the analysis of thermally developed winds relies on the correlation between the mean wind speed and mean temperature. Since the thunderstorm wind is relatively more important for wind engineering, its wind characteristic is focused hereafter and analyzed in detail based on the ultrasonic anemometer data. The characteristics of the thermally developed wind and other wind will be the matter of further studies and investigations. Results show that the characteristics of the thunderstorm wind measured in the mountainous area have no significant difference in comparison with those in the flat area. Due to the limited data, the above results deserve further investigations when more measurements become available. • Field measurement was conducted to study intense wind characteristics in mountain. • Thunderstorm and thermally developed winds (TW, TDW) are spotted in mountain. • TW and TDW are separated out by the proposed automatic classification method. • Transient characteristics of TW in mountain area are well discussed. • Characteristics of TW in mountain area are found to be similar to those in flat area. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the statistical characterization of the wind velocity in complex terrains based on the measured data from unevenly spaced long-term anemometric stations. Three crucial issues are considered: (1) the incompleteness or discontinuity of the long-term datasets and its effects on the statistical analysis; (2) the consistency of the data transfer procedure from a reference site to a target site based on numerical simulations of the wind fields; and, (3) the techniques to transfer and interpolate data from concurrent anemometric datasets to a target site. These aspects are discussed considering, as a reference pilot test case, the wind climate of five port areas in the High Tyrrhenian Sea, namely Genoa, Savona, La Spezia, Livorno and Bastia, studied in the framework of the European project “Wind and Ports”. [Copyright &y& Elsevier]