International high-frequency base balance benchmark study

Holmes, John D.,Tse, Tim K.T. Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.18 No.4

A summary of the main results from an international comparative study for the high-frequency base balance is given. Two buildings were specified - a 'basic' and an 'advanced' building. The latter had more complex dynamic response with coupled modes of vibration. The predicted base moments generally showed good agreement amongst the participating groups, but less good agreement was found for the roof accelerations which are dominated by the resonant response, and subject to measurement errors for the generalized force spectra, to varying mode shape correction techniques, and different methods used for combining acceleration components.

Gust durations, gust factors and gust response factors in wind codes and standards

Holmes, John D.,Allsop, Andrew C.,Ginger, John D. Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.19 No.3

This paper discusses the appropriate duration for basic gust wind speeds in wind loading codes and standards, and in wind engineering generally. Although various proposed definitions are discussed, the 'moving average' gust duration has been widely accepted internationally. The commonly-specified gust duration of 3-seconds, however, is shown to have a significant effect on the high-frequency end of the spectrum of turbulence, and may not be ideally suited for wind engineering purposes. The effective gust durations measured by commonly-used anemometer types are discussed; these are typically considerably shorter than the 'standard' duration of 3 seconds. Using stationary random process theory, the paper gives expected peak factors, $g_u$, as a function of the non-dimensional parameter ($T/{\tau}$), where T is the sample, or reference, time, and ${\tau}$ is the gust duration, and a non-dimensional mean wind speed, $\bar{U}.T/L_u$, where $\bar{U}$ is a mean wind speed, and $L_u$ is the integral length scale of turbulence. The commonly-used Durst relationship, relating gusts of various durations, is shown to correspond to a particular value of turbulence intensity $I_u$, of 16.5%, and is therefore applicable to particular terrain and height situations, and hence should not be applied universally. The effective frontal areas associated with peak gusts of various durations are discussed; this indicates that a gust of 3 seconds has an equivalent frontal area equal to that of a tall building. Finally a generalized gust response factor format, accounting for fluctuating and resonant along-wind loading of structures, applicable to any code is presented.

Gust durations, gust factors and gust response factors in wind codes and standards

John D. Holmes,Andrew C. Allsop,John D. Ginger 한국풍공학회 2014 Wind and Structures, An International Journal (WAS Vol.19 No.3

This paper discusses the appropriate duration for basic gust wind speeds in wind loading codes and standards, and in wind engineering generally. Although various proposed definitions are discussed, the 'moving average' gust duration has been widely accepted internationally. The commonly-specified gust duration of 3-seconds, however, is shown to have a significant effect on the high-frequency end of the spectrum of turbulence, and may not be ideally suited for wind engineering purposes. The effective gust durations measured by commonly-used anemometer types are discussed; these are typically considerably shorter than the 'standard' duration of 3 seconds. Using stationary random process theory, the paper gives expected peak factors, gu, as a function of the non-dimensional parameter (T/ τ), where T is the sample, or reference, time, and τ is the gust duration, and a non-dimensional mean wind speed, U ̅.T /Lu, where U ̅. is a mean wind speed, and Lu is the integral length scale of turbulence. The commonly-used Durst relationship, relating gusts of various durations, is shown to correspond to a particular value of turbulence intensity Iu, of 16.5%, and is therefore applicable to particular terrain and height situations, and hence should not be applied universally. The effective frontal areas associated with peak gusts of various durations are discussed; this indicates that a gust of 3 seconds has an equivalent frontal area equal to that of a tall building. Finally a generalized gust response factor format, accounting for fluctuating and resonant along-wind loading of structures, applicable to any code is presented.

International high-frequency base balance benchmark study

John D. Holmes,Tim K.T. Tse 한국풍공학회 2014 한국풍공학회지 Vol.18 No.4

A summary of the main results from an international comparative study for the high-frequency base balance is given. Two buildings were specified – a 'basic' and an 'advanced' building. The latter had more complex dynamic response with coupled modes of vibration. The predicted base moments generally showed good agreement amongst the participating groups, but less good agreement was found for the roof accelerations which are dominated by the resonant response, and subject to measurement errors for the generalized force spectra, to varying mode shape correction techniques, and different methods used for combining acceleration components.

Effect of building volume and opening size on fluctuating internal pressures

John D. Ginger,John D. Holmes,Gregory A. Kopp 한국풍공학회 2008 Wind and Structures, An International Journal (WAS Vol.11 No.5

This paper considers internal pressure fluctuations for a range of building volumes and dominant wall opening areas. The study recognizes that the air flow in and out of the dominant opening in the envelope generates Helmholtz resonance, which can amplify the internal pressure fluctuations compared to the external pressure, at the opening. Numerical methods were used to estimate fluctuating standard deviation and peak (i.e. design) internal pressures from full-scale measured external pressures. The ratios of standard deviation and peak internal pressures to the external pressures at a dominant windward wall opening of area, AW are presented in terms of the non-dimensional opening size to volume parameter, , where as is the speed of sound, is the mean wind speed at the top of the building and VIe is the effective internal volume. The standard deviation of internal pressure exceeds the external pressures at the opening, for greater than about 0.75, showing increasing amplification with increasing . The peak internal pressure can be expected to exceed the peak external pressure at the opening by 10% to 50%, for greater than about 5. A dominant leeward wall opening also produces similar fluctuating internal pressure characteristics.

Effect of building volume and opening size on fluctuating internal pressures

Ginger, John D.,Holmes, John D.,Kopp, Gregory A. Techno-Press 2008 Wind and Structures, An International Journal (WAS Vol.11 No.5

This paper considers internal pressure fluctuations for a range of building volumes and dominant wall opening areas. The study recognizes that the air flow in and out of the dominant opening in the envelope generates Helmholtz resonance, which can amplify the internal pressure fluctuations compared to the external pressure, at the opening. Numerical methods were used to estimate fluctuating standard deviation and peak (i.e. design) internal pressures from full-scale measured external pressures. The ratios of standard deviation and peak internal pressures to the external pressures at a dominant windward wall opening of area, AW are presented in terms of the non-dimensional opening size to volume parameter, $S^*=(a_s/\bar{U}_h)^2(A_W^{3/2}/V_{Ie})$ where $a_s$ is the speed of sound, $\bar{U}_h$ is the mean wind speed at the top of the building and $V_{Ie}$ is the effective internal volume. The standard deviation of internal pressure exceeds the external pressures at the opening, for $S^*$ greater than about 0.75, showing increasing amplification with increasing $S^*$. The peak internal pressure can be expected to exceed the peak external pressure at the opening by 10% to 50%, for $S^*$ greater than about 5. A dominant leeward wall opening also produces similar fluctuating internal pressure characteristics.

Aspects of the dynamic wind-induced response of structures and codification

Tamura, Yukio,Kareem, Ahsan,Solari, Giovanni,Kwok, Kenny C.S.,Holmes, John D.,Melbourne, William H. Techno-Press 2005 Wind and Structures, An International Journal (WAS Vol.8 No.4

This paper describes the work of the International Association for Wind Engineering Working Group E -Dynamic Response, one of the International Codification Working Groups set up at the Tenth International Conference on Wind Engineering in Copenhagen. Comparisons of gust loading factors and wind-induced responses of major codes and standards are first reviewed, and recent new proposals on 3-D gust loading factor techniques are introduced. Then, the combined effects of along-wind, crosswind and torsional wind load components are discussed, as well as the dynamic characteristics of buildings. Finally, the mathematical forms of along-wind velocity spectra for along-wind response calculation and codification of acceleration criteria are discussed.