Emerging issues and new frameworks for wind loading on structures in mixed climates

Giovanni Solari 한국풍공학회 2014 Wind and Structures, An International Journal (WAS Vol.19 No.3

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.

Proper orthogonal decomposition in wind engineering. Part 1: A state-of-the-art and some prospects

Giovanni Solari,Luigi Carassale,Federica Tubino 한국풍공학회 2007 Wind and Structures, An International Journal (WAS Vol.10 No.2

The Proper Orthogonal Decomposition (POD) is a statistical method particularly suitable and versatile for dealing with many problems concerning wind engineering and several other scientific and humanist fields. POD represents a random process as a linear combination of deterministic functions, the POD modes, modulated by uncorrelated random coefficients, the principal components. It owes its popularity to the property that only few terms of the series are usually needed to capture the most energetic coherent structures of the process, and a link often exists between each dominant mode and the main mechanisms of the phenomenon. For this reason, POD modes are normally used to identify low-dimensional subspaces appropriate for the construction of reduced models. This paper provides a state-of-the-art and some prospects on POD, with special regard to its framework and applications in wind engineering. A wide bibliography is also reported.

Proper orthogonal decomposition in wind engineering - Part 1: A state-of-the-art and some prospects

Solari, Giovanni,Carassale, Luigi,Tubino, Federica Techno-Press 2007 Wind and Structures, An International Journal (WAS Vol.10 No.2

The Proper Orthogonal Decomposition (POD) is a statistical method particularly suitable and versatile for dealing with many problems concerning wind engineering and several other scientific and humanist fields. POD represents a random process as a linear combination of deterministic functions, the POD modes, modulated by uncorrelated random coefficients, the principal components. It owes its popularity to the property that only few terms of the series are usually needed to capture the most energetic coherent structures of the process, and a link often exists between each dominant mode and the main mechanisms of the phenomenon. For this reason, POD modes are normally used to identify low-dimensional subspaces appropriate for the construction of reduced models. This paper provides a state-of-the-art and some prospects on POD, with special regard to its framework and applications in wind engineering. A wide bibliography is also reported.

Investigation of wind actions and effects on the Leaning Tower of Pisa

Solari, Giovanni,Reinhold, Timothy A.,Livesey, Flora Techno-Press 1998 Wind and Structures, An International Journal (WAS Vol.1 No.1

This paper describes wind investigations for the Leaning Tower of Pisa which were conducted as part of an overall evaluation of its behaviour. Normally a short, stiff and heavy building would not be a candidate for detailed wind analyses. However, because of extremely high soil pressures developed from its inclination, there has been increasing concern that environmental loading such as wind actions could combine with existing conditions to cause the collapse of the tower. The studies involved wind assessment at the site as a function of wind direction, analysis of historical wind data to determine extreme wind probabilities of occurrence, estimation of structural properties, analytical and boundary layer wind tunnel investigations of wind loads and evaluation of the response with special concern for loads in the direction of inclination of the tower and significant wake effects from the neighboring cathedral for critical wind directions. The conclusions discuss the role of wind on structural safety, the precision of results attained and possible future studies involving field measurements aimed at validating or improving the analytical and boundary layer wind tunnel based assessments.

Modal transformation tools in structural dynamics and wind engineering

Solari, Giovanni,Carassale, Luigi Techno-Press 2000 Wind and Structures, An International Journal (WAS Vol.3 No.4

Structural dynamics usually applies modal transformation rules aimed at de-coupling and/or minimizing the equations of motion. Proper orthogonal decomposition provides mathematical and conceptual tools to define suitable transformed spaces where a multi-variate and/or multi-dimensional random process is represented as a linear combination of one-variate and one-dimensional uncorrelated processes. Double modal transformation is the joint application of modal analysis and proper orthogonal decomposition applied to the loading process. By adopting this method the structural response is expressed as a double series expansion in which structural and loading mode contributions are superimposed. The simultaneous use of the structural modal truncation, the loading modal truncation and the cross-modal orthogonality property leads to efficient solutions that take into account only a few structural and loading modes. In addition the physical mechanisms of the dynamic response are clarified and interpreted.

Characteristics of thunderstorms relevant to the wind loading of structures

Solari, Giovanni,Burlando, Massimiliano,De Gaetano, Patrizia,Repetto, Maria Pia Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.6

"Wind and Ports" is a European project that has been carried out since 2009 to handle wind forecast in port areas through an integrated system made up of an extensive in-situ wind monitoring network, the numerical simulation of wind fields, the statistical analysis of wind climate, and algorithms for medium-term (1-3 days) and short term (0.5-2 hours) wind forecasting. The in-situ wind monitoring network, currently made up of 22 ultrasonic anemometers, provides a unique opportunity for detecting high resolution thunderstorm records and studying their dominant characteristics relevant to wind engineering with special concern for wind actions on structures. In such a framework, the wind velocity of thunderstorms is firstly decomposed into the sum of a slowly-varying mean part plus a residual fluctuation dealt with as a non-stationary random process. The fluctuation, in turn, is expressed as the product of its slowly-varying standard deviation by a reduced turbulence component dealt with as a rapidly-varying stationary Gaussian random process with zero mean and unit standard deviation. The extraction of the mean part of the wind velocity is carried out through a moving average filter, and the effect of the moving average period on the statistical properties of the decomposed signals is evaluated. Among other aspects, special attention is given to the thunderstorm duration, the turbulence intensity, the power spectral density and the integral length scale. Some noteworthy wind velocity ratios that play a crucial role in the thunderstorm loading and response of structures are also analyzed.

Emerging issues and new frameworks for wind loading on structures in mixed climates

Solari, Giovanni Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.19 No.3

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.

Brâncuşi Endless Column: A Masterpiece of Art and Engineering

Solari, Giovanni Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.3

The Endless Column by Constantin Brancu?i is "the most radical sculpture in the history of classic modernism", "the only one of modern times that can be compared with the great Egyptian, Greek and Renaissance monuments". It "is not only an artistic masterpiece, but also an extraordinary feat of engineering", the greatest example of collaboration between a sculptor and an engineer. This article illustrates the path that led the artist to conception of the column, its planning and construction, the investigations on preservation of the monument and its restoration, the aerodynamic tests in the wind tunnel, the modeling of the wind and the structure in virtue of which the aeroelastic instability, dynamic response and fatigue life were investigated. The conclusions discuss the column's role in the panorama of the great works of modern engineering.

Characteristics of thunderstorms relevant to the wind loading of structures

Giovanni Solari,Massimiliano Burlando,Patrizia De Gaetano,Maria Pia Repetto 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.6

“Wind and Ports” is a European project that has been carried out since 2009 to handle wind forecast in port areas through an integrated system made up of an extensive in-situ wind monitoring network, the numerical simulation of wind fields, the statistical analysis of wind climate, and algorithms for medium-term (1-3 days) and short term (0.5-2 hours) wind forecasting. The in-situ wind monitoring network, currently made up of 22 ultrasonic anemometers, provides a unique opportunity for detecting high resolution thunderstorm records and studying their dominant characteristics relevant to wind engineering with special concern for wind actions on structures. In such a framework, the wind velocity of thunderstorms is firstly decomposed into the sum of a slowly-varying mean part plus a residual fluctuation dealt with as a non-stationary random process. The fluctuation, in turn, is expressed as the product of its slowly-varying standard deviation by a reduced turbulence component dealt with as a rapidly-varying stationary Gaussian random process with zero mean and unit standard deviation. The extraction of the mean part of the wind velocity is carried out through a moving average filter, and the effect of the moving average period on the statistical properties of the decomposed signals is evaluated. Among other aspects, special attention is given to the thunderstorm duration, the turbulence intensity, the power spectral density and the integral length scale. Some noteworthy wind velocity ratios that play a crucial role in the thunderstorm loading and response of structures are also analyzed.

3-D wind-induced effects on bridges during balanced cantilever erection stages

Schmidt, Stefan,Solari, Giovanni Techno-Press 2003 Wind and Structures, An International Journal (WAS Vol.6 No.1

Nowadays balanced cantilever construction plays an essential role as a sophisticated erection technique of bridges due to its economical and ecological advantages. Experience teaches that wind has a great importance with regard to this construction technique, but methods proposed by codes to take wind effects into account are still rather crude and, in most cases, completely lacking. Also research in this field is quite limited and aimed at studying only the longitudinal shear and the torque at the pier base, caused by the mean wind velocity and by the longitudinal turbulence actions over the deck. This paper advances the present solutions by developing a new procedure that takes into account all wind effects both on the deck and on the pier. The proposed model assumes the mean wind velocity as orthogonal to the bridge plane and considers the effects produced by all the three turbulence components and by the vortex shedding. The applications point out the role of each loading component on different bridge configurations and show that disregarding the presence of some effects may imply oversimplified results and relevant underestimations.