Advances in Wind Engineering

402 Pages·1989·39.585 MB·English

by  C. Kramer and H.J. Gerhardt (Eds.)

ADVANCES IN
WIND
ENGINEERING
Proceedings of the 7th International Congress on Wind Engineering
held under the auspices of the International Association for Wind Engineering
Aachen, F.R.G., July 6-10,1987
Parti
Edited by
C. Kramer and H.J. Gerhardt
Fachhochschule Aachen, F.R.G.
This material has also been published as a special issue of the Journal of
Wind Engineering and Industrial Aerodynamics, Vols. 28-30
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xi
INTERNATIONAL ASSOCIATION FOR WIND ENGINEERING
The International Association for Wind Engineering (IAWE) came
into being on 10 September 1975 through action of the Steering
Committee for the International Study Group on Wind Effects on
Buildings and Structures. According to the by-laws presented at
the 6th International Conference on Wind Engineering in Australia
in 1983 and ratificated at the 7th International Conference on
Wind Engineering in Germany in 1987 the primary purposes of the
I AWE are:
(1) Organization of international meetings
(2) Liaison with national and international
organizations working in similar fields.
After the first Conference in Teddington, England, almost 25
years ago, the second Conference has been held in Ottawa, Canada
(1967), the third in Tokyo, Japan (1971), the fourth in Heathrow,
England (1975), the fifth in Fort Collins, Colorado, USA (1979)
and the sixth at the Gold Coast, Australia and in Auckland, New
Zealand (1983). At this Sixth International Conference on Wind
Engineering the Steering Committee of the International Associa­
tion for Wind Engineering accepted an invitation from Germany to
host the 7th International Conference on Wind Engineering.
The minutes of the Steering Committee meeting of the Internation­
al Association for Wind Engineering held during the 7th Interna­
tional Conference on Wind Engineering are presented as an appen­
dix to these proceedings.
xiii
THE CONFERENCE
The 7th International Conference on Wind Engineering in Aachen
was held at a time when the 7th Colloquium of the biannual Collo­
quium on Industrial Aerodynamics should have taken place. The
organisers of the 7th International Conference were very proud to
host the International Conference instead of the Industrial Aero­
dynamics Colloquium. Two hundred and twenty six delegates from
twenty three countries took part in this conference.
More than 250 papers had been submitted for the Conference. These
were far more papers than could be presented at a conference with
no parallel sessions. Due to the high standard of so many papers
the Organizing Committee decided to have about 90 papers present­
ed in full length and, in addition, asked General Reporters to
summarize some interesting and valuable papers.
It was not easy to decide on which papers to select. Therefore,
the Organizing Committe gratefully accepted the assistance of
collegues with international reputation from the family of wind
engineers in various European countries. These collegues together
with members of the Organizing Committee formed the Paper Selec­
tion Committee. The members were:
P. Bearman, United Kingdom H. van Koten, The Netherlands
E. Berger, Germany J.R. Mayne, United Kingdom
G. Berz, Germany H.J. Niemann, Germany
N.J. Cook, United Kingdom D. Olivari, Belgium
I.R. Harris, United Kingdom E. Plate, Germany
J.A. Hertig, Switzerland H. Ruscheweyh, Germany
H. Hirtz, Germany H. Schroers, Germany
D.J. Johns, Hong Kong H. Sockel, Austria
Chairman: H.J. Gerhardt, Germany
The papers presented by their authors, the summaries of the
General Reporters and the Session Discussions and editorial com­
ments of the Session Chairmen are presented in these Proceedings
of the 7th International Conference on Wind Engineering.
XV
PROGRAM SUMMARY
The Conference Sessions were held at the EUROGRESS Congress
Centre in Aachen.
Monday, July 6
Morning Opening Adresses by
Prof. Dr.-Ing. C. Kramer, Chairman of the I AWE and
the Conference Organizing Committee
Prof. Dr. med. H.D. Ohlenbusch, Rektor of the Aachen
Technical University
Prof. Dipl.-Ing. R. Flossdorf, Rektor of the
Fachhochschule Aachen
Baudirektor Dipl.-Ing. H. Hirtz, Institut fiir
Bautechnik, Berlin
Session 1 Wind Characteristics and Description
Afternoon Session 2 Wind Environment
Session 3 Fundamental Studies
Evening Reception of the delegates by the Mayor of Aachen
Tuesday, July 7
Morning Session 3 Fundamental Studies (cont.)
Afternoon Session 4 High Rise Buildings
Evening IAWE Steering Committee Meeting
Wednesday, July 8
Morning Session 5 Low Rise Structures - Local Wind Loads
Afternoon Session 6 Low Rise Structures
- Wind Shelter and
Wind Drifting
Evening Conference Dinner
Thursday, July 9
Morning Session 7 Low Rise Structures - Wind Loading and
Flow Field
Afternoon Session 8 Engineering Structures - Bridges
Friday, July 10
Morning Session 9 Engineering Structures - Towers, Cables,
Wind Pressures and Fatigue
Afternoon Session 10 Codification
Session 11 Wind Engineering and Hazard
Besides the above program it was possible to visit technical
facilities of some laboratories. The program was completed by a
Guest Program with tours in the vicinity of Aachen.
xvii
ACKNOWLEDGMENTS
A large international conference like the Seventh International
Conference on Wind Engineering always requires, besides the
scientific preparation a high effort of organizational adminis­
trative work. At the Seventh International Conference on Wind
Engineering this work load had to be carried by only a rather
small group and I wish to express my sincere thanks to this group
for their excellent performance.
The Local Organizing Group was supported effectively by the
National Organizing Committee, the members of these two groups
are listed in the appendix. I give very special thanks to our
conference secretary, Ms. Margarete Hilgers, who was the most
active center point of all the preparations and organizational
affairs from the very first beginning of the conference organiza­
tion until finalizing of the conference proceedings.
I express my sincere thanks to the members of the Paper Selection
Committee and especially to my collegue Prof. H.J. Gerhardt as
Chairman of this committee. This committee performed a very dif­
ficult job to select only 90 presentations out of about 250
mostly very excellent papers.
Grateful acknowledgement and thanks are expressed to the follow­
ing sponsors who gave financial or moral support to the confer­
ence:
Fachhochschule Aachen
Aachen Technical University, Institut fur Stahlbau
Journal of Industrial Aerodynamics and Wind Engineering
U.S. National Science Foundation (NSF)
International Association for Bridge and Structural Engineering
Europaische Kommission fur Stahl
Deutscher Strahlbauverband
Institut flir Bautechnik, Berlin
Philipp Holzmann AG, Frankfurt
Mero Raumstruktur GmbH & Co. Wurzburg
Goldbeckbau GmbH, Bielefeld
C. Kramer
SESSION 1
WIND CHARACTERISTICS AND DESCRIPTION
CHAIRMAN
J. Wieringa
Koninklijk Nederlands Meteorologisch Institut
De Bilt, Netherlands
CO-CHAIRMAN
H. Ruscheweyh
Institut fiir Stahlbau
Aachen Technical University
Aachen, Germany
GENERAL REPORTER
A.J. Bowen
Mechanical Engineering Department
University of Canterbury
Christchurch, New Zealand
Journal of Wind Engineering and Industrial Aerodynamics, 28 (1988) 3-9 3
Elsevier Science Publishers B.V., Amsterdam — Printed in The Netherlands
REVIEW OF PAPERS FOR SESSION 1 : WIND CHARACTERISTICS AND DESCRIPTION
A.J. BOWEN
Mechanical Engineering Department, University of Canterbury, Christchurch
New Zealand.
It is my pleasure to introduce the first Conference Session on Wind
Characteristics and Description and to present a brief review of seven sub­
mitted papers which are unable to be presented in full at this Conference.
While browsing over the proceedings of the previous four Conferences on
Wind Engineering together with the present list of papers, it became apparent
that the general goals of most engineering-related investigations into wind
structure have not changed significantly over those sixteen years. However
the growing demand for less conservative and therefore more economic structural
designs has produced a strong need for improved accuracy in the prediction of
wind loadings. There is therefore an urgent need for a significant improvement
in the accuracy of the basic wind speed data and in the understanding of atmos­
pheric turbulence which is available to the practising engineer. Progress in
gathering more accurate models for the wind characteristics under any signifi­
cant climatic event must keep pace with the outstanding improvements evident
in our understanding of the distribution of pressure coefficients around a
particular building shape and in the dynamic loading prediction techniques.
The overall design is only as accurate as the accuracy of each of its parts,
including the information used to define the design wind characteristics.
Developments in our understanding of wind characteristics for engineer­
ing purposes have been aptly categorised by Professor Hans Panofsky at the 1975
Wind Engineering Conference at Heathrow, London and these categories are still
relevant today. The papers submitted to this Conference Session may also be
grouped into the same categories for the purpose of this discussion.
LONG-PERIOD WIND STATISTICS
The formulation of more accurate methods of analysis and the accumula­
tion of more accurate extreme wind speed statistics for the codified prediction
of Basic Wind Speeds are still necessary. There is lately an increased
interest in the extreme wind statistics of short term or local violent storms
not normally identifiable in mean wind data. For example, in the occurrence
4
of thunderstorms and their seasonal and directional dependence. Before proces­
sing, the wind speed data must be fully corrected for terrain and roughness
effects and indeed, some of today's papers address these aspects.
The first paper in this category by Riera and Nanni (1) reports the re­
sults of a pilot study of wind velocity data gathered over 25 years at four
stations in Southern Brazil. The main objective was the development of data
gathering and processing procedures to be used in the subsequent analysis of
records from about 80 other stations throughout Brazil.
The specific issues investigated were;
a) influence of storm type (storms generated by mature pressure,
systems as distinct from local intense thunderstorms),
b) influence of wind direction,
c) the feasibility of a scheme for regional predictions.
Thunderstorms were identified by the short duration of the intense wind
activity and from visual observations. Winds over 13 knots were classified as
an extreme wind event. The maximum 2-3 second average gust velocity was re­
corded for each event and corrected to standard site conditions.
The authors concluded that;
a) There was statistical evidence justifying the independent
processing of major storm and local thunderstorm events.
b) For individual sectors of direction and storm type, the
extreme type I (Gumbel) probability distribution presented
the best fit.
c) For combined wind events, the data departed significantly
from the type I distribution.
d) Regression techniques described in the paper appeared to
adequately account for the influence of geographical location
and wind orientation.
The second paper by Tamura and Suda (2) shows that the steady decrease
in the annual maximum wind speeds measured throughout Japan at the weather
stations may be attributed to the steady increase in ground roughness due to
long term building development rather than due to an overall decrease in the
number of severe typhoons afflicting that country. Data are presented show­
ing that the yearly values of both the daily maximum and annual mean wind
speeds have been dropping steadily since about 1960.
In contrast, the ground roughness around the weather stations is known
to have increased steadily. However, as there were no available data indica­
ting this trend in ground roughness in quantitative terms, an indirect method
was developed based on building density figures. The total floor areas of all
taxed buildings were obtained from the fixed property tax ledgers in the Public
5
Offices of each administrative area and the building density estimated using an
empirical relationship developed in an earlier reference. The effects of the
more steady natural background roughness were also discussed.
Close correlation was found between the variations of the annual maximum
wind speed and the building density averaged in Japan overall. Suitable correc­
tions for the increase in ground roughness were applied to wind data for the
whole country and for 12 chosen measurement sites. It was shown that the
corrected wind speeds fitted the return period wind speed type-I distribution
significantly better than the present uncorrected wind speeds in 8 cases. This
left 4 sites which had significant terrain features with no improvement.
The authors conclude that although the meteorological variation cannot
be denied, the effect of ground roughness variation with time is of the same
order of magnitude.
STRUCTURE OF WINDS OVER SIMPLE TERRAIN
The development in understanding and the collection of more accurate
wind turbulence data for quasi-static peak loads and dynamic wind load predic­
tions under strong-wind neutrally-stable conditions are continuing. However,
this is probably the only category where we are reasonably confident in the
adequacy of the existing available models.
The first paper in this category by Flaga and Wrana (3) gives an
assessment of the various empirical formulae describing the power spectral
densities of the three turbulent velocity components that are currently en­
countered in the literature and in common use in engineering practice.
Their critical review resulted in the following conclusions;
a) The values of particular component spectra are dispersed, both in
the range of frequencies significant to tall and slender structures
(0.1-5 Hz) and at the low frequency range. These significant
variations between model frequencies could cause errors of some
hundreds of percent when estimating the dynamic response.
b) In contrast to some early spectral models and codes, the spectra
must be a function of height, especially for the estimation of
tall building response.
c) Vertical and lateral velocity fluctuations are often neglected in
engineering practice as being insignificant, but for the higher
frequencies, spectra concerning these two components are comparable
in magnitude to the longitudinal velocity spectrum.
The second paper by Tieleman (4) is a review of the limited amount
of data available in the literature that provide reliable information on the
mean and turbulent flow in the surface layer over the ocean, with the wind