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Windborne debris and damage risk models: a review
J.D. Holmes 한국풍공학회 2010 Wind and Structures, An International Journal (WAS Vol.13 No.2
This review paper discusses research from the last few years relating to windborne debris risk models and the essential elements of engineering damage prediction models. Generic types of windborne debris are discussed. The results of studies of debris trajectories that are relevant to damage models are described - in particular the horizontal component of debris velocity as a function of distance travelled. The merits of impact momentum versus impact kinetic energy as a relevant parameter for predicting damage are considered, and how published data from generic cannon impact tests can be used in risk models. The quantitative variation of debris impact damage with wind speed is also discussed. Finally the main elements of previously-proposed debris damage models are described.
Extreme wind prediction and zoning
Holmes, J.D.,Kasperski, M.,Miller, C.A.,Zuranski, J.A.,Choi, E.C.C. Techno-Press 2005 Wind and Structures, An International Journal (WAS Vol.8 No.4
The paper describes the work of the IAWE Working Group WGF - Extreme Wind Prediction and Zoning, one of the international codification working groups set up in 2000. The topics covered are: the international database of extreme winds, quality assurance and data quality, averaging times, return periods, probability distributions and fitting methods, mixed wind climates, directionality effects, the influence of orography, rare events and simulation methods, long-term climate change, and zoning and mapping. Recommendations are given to promote the future alignment of international codes and standards for wind loading.
Wind structure and codification
Holmes, J.D.,Baker, C.J.,English, E.C.,Choi, E.C.C. Techno-Press 2005 Wind and Structures, An International Journal (WAS Vol.8 No.4
The paper describes the work of the Working Group on Wind Structure, one of the International Codification Working Groups set up by the International Association of Wind Engineering in 1999. The topics of terrain and exposure, shielding and shelter, topographic effects, tropical cyclone and hurricane wind structure, and thunderstorm wind structure, are described with emphasis on their codification in wind loading codes and standards. Recommendations from the working group are given.
A forensic study of the Lubbock-Reese downdraft of 2002
J. D. Holmes,H. M. Hangan,J. L. Schroeder,C. W. Letchford,K. D. Orwig 한국풍공학회 2008 Wind and Structures, An International Journal (WAS Vol.11 No.2
This paper discusses engineering aspects of the rear-flank downdraft that was recorded near Lubbock, Texas on 4 June 2002, and produced a gust wind speed nearly equal to the design value (50-year return period) for the region. The general characteristics of the storm, and the decomposition of the time histories into deterministic ‘running mean’ and random turbulence components are discussed. The fluctuating wind speeds generated by the event can be represented as a dominant low-frequency ‘running-mean’, with superimposed random turbulence of higher frequencies. Spectral and correlation characteristics of the residual turbulence are found to be similar to those of high-frequency turbulence in boundary-layer winds. However, the low-frequency components in the running-mean wind speeds are spatially homogeneous, in contrast to the low-frequency turbulence found in synoptic boundary-layer winds. With respect to transmission line design, this results in significantly higher ‘span reduction factors’.
A forensic study of the Lubbock-Reese downdraft of 2002
Holmes, J.D.,Hangan, H.M.,Schroeder, J.L.,Letchford, C.W.,Orwig, K.D. Techno-Press 2008 Wind and Structures, An International Journal (WAS Vol.11 No.2
This paper discusses engineering aspects of the rear-flank downdraft that was recorded near Lubbock, Texas on 4 June 2002, and produced a gust wind speed nearly equal to the design value (50-year return period) for the region. The general characteristics of the storm, and the decomposition of the time histories into deterministic 'running mean' and random turbulence components are discussed. The fluctuating wind speeds generated by the event can be represented as a dominant low-frequency 'running mean' with superimposed random turbulence of higher frequencies. Spectral and correlation characteristics of the residual turbulence are found to be similar to those of high-frequency turbulence in boundary-layer winds. However, the low-frequency components in the running-mean wind speeds are spatially homogeneous, in contrast to the low-frequency turbulence found in synoptic boundary-layer winds. With respect to transmission line design, this results in significantly higher 'span reduction factors'.
J. Riedel,D. G. Holmes,B. P. McGrath 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Dual Active Bridge (DAB) converters offer an unmatched capability to transfer energy in either direction between two DC sources, while also providing galvanic isolation and high conversion efficiency. However, to operate at high efficiencies, the bridges must operate with Zero-Voltage-Switching (ZVS) over as wide an operating range as possible. The conventional approach to determine ZVS operation uses time domain analysis with ideal AC coupling inductances, which only approximately identifies the ZVS boundaries. This paper proposes a new approach using frequency domain analysis of the bridge switching patterns, which accurately predicts the ZVS boundaries over a full range of operating conditions while also accommodating more complex AC coupling structures and practical impedance non-idealities. An exact theoretical analysis is presented for two level modulation of the two bridges coupled through a general impedance structure. An analytical solution is then presented for a single coupling impedance, while boundaries for more complex coupling structures and practical impedances are solved by numerical integration. ZVS boundaries for selected systems are validated by matching simulation and experimental results.
Windborne debris and damage risk models: a review
Holmes, J.D. Techno-Press 2010 Wind and Structures, An International Journal (WAS Vol.13 No.2
This review paper discusses research from the last few years relating to windborne debris risk models and the essential elements of engineering damage prediction models. Generic types of windborne debris are discussed. The results of studies of debris trajectories that are relevant to damage models are described - in particular the horizontal component of debris velocity as a function of distance travelled. The merits of impact momentum versus impact kinetic energy as a relevant parameter for predicting damage are considered, and how published data from generic cannon Impact tests can be used in risk models. The quantitative variation of debris impact damage with wind speed is also discussed. Finally the main elements of previously-proposed debris damage models are described.