• Wind and Structures
• /
• 제8권4호
• /
• pp.283-294
• /
• 2005

This paper describes the work of the Working Group on wind pressure coefficients on low-rise structures, one of the groups set up by the International Association of Wind Engineering in 1999. General aspects of wind loading on low-rise structures are summarized. The definition, derivation and codification of loading coefficients is described. Comparisons of pressure coefficients on low rise structures are made between a selection of wind loading standards. Recommendations for consistency and for the harmonization of these coefficients are given.

• Wind and Structures
• /
• 제8권4호
• /
• pp.235-250
• /
• 2005

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.

• Wind and Structures
• /
• 제8권4호
• /
• pp.251-268
• /
• 2005

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.

• Wind and Structures
• /
• 제22권1호
• /
• pp.65-87
• /
• 2016

The wind velocity profile over the height of a structure in high intensity wind (HIW) events, such as downbursts, differs from that associated with atmospheric boundary layer (ABL) winds. Current design codes for lattice transmission structures contain only limited advice on the treatment of HIW effects, and structural design is carried out using wind load profiles and response factors derived for ABL winds. The present study assesses the load-deformation curve (capacity curve) of a transmission tower under modeled downburst wind loading, and compares it with that obtained for an ABL wind loading profile. The analysis considers nonlinear inelastic response under simulated downburst wind fields. The capacity curve is represented using the relationship between the base shear and the maximum tip displacement. The results indicate that the capacity curve remains relatively consistent between different downburst scenarios and an ABL loading profile. The use of the capacity curve avoids the difficulty associated with defining a reference wind speed and corresponding wind profile that are adequate and applicable for downburst and ABL winds, thereby allowing a direct comparison of response under synoptic and downburst events. Uncertainty propagation analysis is carried out to evaluate the tower capacity by considering the uncertainty in material properties and geometric variables. The results indicated the coefficient of variation of the tower capacity is small compared to those associated with extreme wind speeds.

• Wind and Structures
• /
• 제19권3호
• /
• pp.339-352
• /
• 2014

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.

• Wind and Structures
• /
• 제22권2호
• /
• pp.133-160
• /
• 2016

Hurricanes are among the most costly natural hazards to impact buildings in coastal regions. Building roofs are designed using the wind load provisions of building codes and standards and, in the case of large buildings, wind tunnel tests. Wind permeable roof claddings like roof pavers are not well dealt with in many existing building codes and standards. The objective of this paper is to develop simple guidance in code format for design of loose-laid roof pavers. Large-scale experiments were performed to investigate the wind loading on concrete roof pavers on the flat roof of a low-rise building in Wall of Wind, a large-scale hurricane testing facility at Florida International University. They included wind blow-off tests and pressure measurements on the top and bottom surfaces of pavers. Based on the experimental results simplified guidelines are developed for design of loose-laid roof pavers against wind uplift. The guidelines are formatted so that use can be made of the existing information in codes and standards such as American Society of Civil Engineering (ASCE) 7-10 standard's pressure coefficients for components and cladding. The effects of the pavers' edge-gap to spacer height ratio and parapet height to building height ratio are included in the guidelines as adjustment factors.

• Wind and Structures
• /
• 제8권4호
• /
• pp.269-281
• /
• 2005

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 and Structures
• /
• 제15권2호
• /
• pp.177-188
• /
• 2012

The meteorological events that cause most strong winds in Brazil are extra-tropical cyclones, downbursts and tornadoes. However, one hurricane formed off the coastline of southern Brazil in 2005, a tropical storm formed in 2010 and there are predictions that others may form again. Events such as those described in the paper and which have occurred before 1987, generate data for the wind map presented in the Brazilian wind loading code NBR-6123. This wind map presents the reference wind speeds based on 3-second gust wind speed at 10 m height in open terrain, with 50-year return period, varying from 30 m/s (north half of country) to 50 m/s (extreme south). There is not a separation of the type of climatological event which generated each registered velocity. Therefore, a thunderstorm (TS), an extra-tropical pressure system (EPS) or even a tropical cyclone (TC) are treated the same and its resulting velocities absorbed without differentiation. Since the flow fields generated by each type of meteorological event may be distinct, the indiscriminate combination of the highest wind velocities with aerodynamic coefficients from boundary layer wind tunnels may lead to erroneous loading in buildings.

• Wind and Structures
• /
• 제1권4호
• /
• pp.303-315
• /
• 1998

Full-scale measurements have been made to determine the increase in wind speed over two exposed embankments, one of $23^{\circ}$ slope and 4.7 m in height, the other of $24^{\circ}$ slope and 7.3 m in height. Measurements were made at heights of 5, 10 and 15 m above the upper edge of each embankment and at the same heights approximately 100 m upwind in the lower-level approach fetch. Despite the modest sizes of the embankments, the maximum recorded increase in mean wind speed was 28% and the minimum was 13%; these increase relate to increases in wind loads on structures erected at the top of the embankments of 64% and 28% respectively. The associated increases in gust speeds are estimated at 33% and 18%, which imply increases in gust loading of 77% and 39% respectively. These experimental results are compared with predictions obtained from a computational fluid dynamics (CFD) analysis, using three high Reynolds number eddy-viscosity models and estimates from the UK wind loading code, BS 6399: Part 2. The CFD results are generally in agreement with the experimental data, although near-ground effects on the embankment crest are poorly reproduced.

• Wind and Structures
• /
• 제37권2호
• /
• pp.105-115
• /
• 2023

Structural design includes calculation of the wind speed as one of the major steps in the design process for wind loading. Accurate determination of design wind speed is vital in achieving safety that is consistent with the economy of construction. It is noticeable that many countries and regions such as Hong Kong, Japan and Australia regularly make amendments to improve the accuracy of wind load estimations for their wind codes and standards. This study compares the latest Hong Kong wind code published in 2019, which is generally known as the Code of Practice on Wind Effects in Hong Kong - 2019, with the latest revision of the AIJ Recommendations for Loads on Buildings - 2015 (Japan), and the Australian/New Zealand Standard, AS/NZS 1170.2:2021. The comparisons include the variations between the design wind speed and the vertical profiles of wind speed multipliers. The primary purpose of this study was to show any differences in the basic design wind speed and exposure factor estimations among the three economies located in the Western Pacific Ocean. Subsequently, the reasons for such underlying variations between the three documents, are discussed, together with future development trends.