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The coarse root systems of 24 Sitka spruce (Picea sitchensis (Bong.) Carr.) trees, from a 40-year-old plantation in west Scotland, were extracted, digitised in three dimensions, and root topology was recorded. Roots were from trees grown on a steep (ca. 30°) north-facing slope, and from an adjacent horizontal area with similar gleyed mineral soil. The prevailing wind was across-slope from the west. Analysis of below-ground parts of the trees in comparison with those above-ground revealed a positive linear relationship between coarse root volume and stem volume. Most non-directional characteristics of the root systems were similar between trees on the slope and on flat terrain. Allocation of root mass around trees was examined in relation to the slope and the prevailing wind direction. Trees on the horizontal area had more root mass in leeward sectors than other sectors, but trees on the slopes had more root mass in the windward sectors than other sectors. Centres of mass of the root systems from the horizontal part of the site were not significantly clustered in any direction, but root systems of trees on the slope had centres of mass significantly clustered across the slope in the windward direction. For trees on the slope, the mean direction of the largest sector without structural roots was 4° from north, i.e. downslope. The results are discussed in relation to soil characteristics and the biomechanical behaviour of trees on slopes.

International audience; Pour modéliser l'action du vent sur les structures, on génère des signaux représentatifs du vent à l'aide d'un modèle semi déterministe. Ce dernier est basé, d'une part, sur des réseaux de neurones artificiels, utilisant des données météo régionales, qui permettent de générer les fluctuations lentes, et d'autre part, sur un modèle classique de génération de processus stochastiques, utilisant des formules de densité spectrale empiriques, qui permet de générer les fluctuations turbulentes. Une procédure de vérification, basée sur la transformation en ondelettes continues, montre que seules les échelles de temps supérieures à 20000s (grandes échelles de temps) sont correctement reconstruites à l'aide des réseaux de neurones. Abstract : To compute wind action on structures, wind-speed time series are generated by using a semi-deterministic model. Artificial neural networks are used, with regional meteorological observations as input arguments, to generate the slowly varying wind speed component. Validation tests, using discrete wavelet transform, show that this model is only able to simulate timescales larger than 20000s. So the turbulent wind speed fluctuations are generated, as stochastic processes, by using a traditional method which uses analytical power spectrum formula.

This paper outlines the methods that have been used to determine the frequencies and modes of vibration of multistory buildings from their wind-induced vibrations. Three buildings of ten, thirty-eight and forty-seven stories were investigated. A simple theoretical model was used to calculate the frequencies of vibration of the buildings; the model was based on the assumption that there was no joint rotation in the building frames. A comparison of the theoretical and measured values of the frequencies showed that this simple model was a realistic representation of only the smaller building. It is concluded that a model that includes joint rotation would be more realistic for the taller buildings. Auto-correlation and power spectrum analysis of the vibration records were used to obtain an estimate of the damping characteristics of the buildings. The values obtained were 1 to 3 per cent of the critical amount of damping.

During 1960-62, DBR/NRC conducted air leakage measurements on two single-story houses built during the nineteen fifties using the tracer gas technique. It was followed several years later in 1967-68 by the measurement of the air leakage characteristics of their enclosures using the house pressurization technique. The results of these tests on the two houses were used to develop a procedure for calculating infiltration rates similar to the one recently developed for high-rise buildings. Also, research needs were identified so that the calculation procedure can be applied to houses of different design, construction and wind exposure., Presented at the 1979 ASHRAE Semiannual Meeting, Philadelphia, PA, USA, Jan 28-Feb 1, 1979

This report presents typical measurements of wind-induced movements in the Bank of Commerce Building in Toronto, Canada, part of a long-term project to assess the validity of current wind tunnel techniques in building design. Since current design procedures are based mainly on results from wind tunnel experiments, some full-scale verification is deemed essential. The report concludes with a preliminary assessment of the correlations between measured building movements, those predicted from wind tunnel tests performed for the building design, and displacements computed by the detailed procedure contained in Supplement No. 4 to the National Building Code of Canada, 1977 Edition., Proceedings of the 3rd Colloquium on Industrial Aerodynamics: 14 June 1978, Aachen, Germany

With the rapidly rising energy costs and a growing need to conserve energy, more and more buildings are being analyzed for energy effectiveness using sophisticated computer programs. One problem inherent in these programs is the lack of an accurate but simple method for estimating air infiltration rate, which is known to be a significant component of the energy consumption. To develop such a method, a computer study of air leakage characteristics was made for tall buildings using surface wind pressure data obtained in a boundary layer wind tunnel. The results for a fully exposed tall building in a suburban area were reported by Shaw and Tamura. This paper presents new data on pressure distributions over the faces of a tall building surrounded by lower structures of uniform height. The building and the surrounding structures are separated from each other by a distance equivalent to that of a street and sidewalks. Equations for predicting air infiltration rate have been derived using basically the same method as in the paper for fully exposed tall buildings. These equations are strictly valid only for a tall building surrounded by lower structures of approximately equal height. They may not be generalized for a tall building partially protected by another tall building unless the buildings are sufficiently far apart.

By applying the pressure data obtained from a wind tunnel model study to a computer model building, a simple procedure for calculating exterior wall pressure differences and air infiltration rates for various wind velocities and direction was developed. This study has indicated that the overall infiltration rate is governed by the larger of the two motive forces and that the exterior wall pressure differences at any level caused by wind and stack action are additive., Presented at the 1977 ASHRAE Annual Meeting, Halifax, NS, Canada, June 26-30, 1977

A computer study of smoke movement using a mathematical model of a 20-storey building is described. The model is based on measured air leakage characteristics of four tall office buildings. The results indicate the relative influence of a number of features governing smoke movement in buildings. Smoke concentration patterns caused by stack effect are determined for both steady and transient conditions., Reprinted from ASHRAE Transactions, vol. 75, Part II, 1969, p.81-92., 1969 ASHRAE Semi-Annual Meeting, June 30 - July 2, 1969, Denver, Colorado, USA

Air that leaks through the exterior envelope of a building is a significant component of the heating, cooling and moisture loads of heating, ventilating, and air-conditioning systems. The prediction of air migration routes and flow rates within a building is also important in relation to the control of contaminants, such as smoke and odours. This paper describes a procedure for calculating air flows and pressure differentials that will occur in a multi-storey building as a result of a combination of wind effect, stack effect, and operation of air-handling systems., 2nd Symposium on the Use of Computers for Thermal Environmental Engineering, 1974, Paris, France

The influence of wind and other factors on snow loads on roofs has been recognized in the National Building Code of Canada since 1965. Guidance for common types and shapes of roofs is provided in the 1970 edition of the Code in the Chapter "Coefficients for snow loads on roofs" in Supplement No. 4, Canadian Structural Design Manual. To assist with unusual types of roofs and conditions a collection of case histories, "Snow accumulations in Canada, Case histories: I" was published in January 1967 (NRC 9287). Case histories: II is an expansion and amplification of Case histories: I.

This series of five papers translated from Russian discusses the problems that face the designer of housing in northern areas of the USSR, which are not dissimilar from those occurring in Canada. Existing designs are appraised and their limitations discussed in terms of room layout, window arrangement and their general adaptability to local climatic conditions. The effect of wind in the winter on the thermal performance of housing and on snow accumulation around buildings has received particular emphasis, and methods of modifying these effects by proper design and ventilation are analyzed. Papers included are: "Plans of housing units for the Far East", "The special characteristics of planning and construction in the Far North", "Methods of construction for protection against the wind", "On a housing standard for the Arctic" and "The need for satisfactory sets of standard housing and design for regions with a severe climate".

La présent étude examine les emplois et les limites des mé thodes actuelles permettant d'évaluer l'imperméabilité à la pluie, de même que les études déjà menées par la DRB/CNRC en vue de recueillir des renseignements propres à amélior la pré vision de l'imperméabilité., Recherche à la Pratique : Le Défi de L'application. CIB 5e Congrès: 1971-06, Versailles, France

The current status of North and South American research on the prediction of tall building behaviour in response to wind is reviewed under the headings, meteorological research on wind structure and climate, full-scale tests, development of wind tunnel techniques, and simplified prediction formulae for gust effects. The need for cooperation in gathering and applying both full-scale and wind tunnel data is stressed. Over forty references published in the last ten years are given, arranged chronologically under each of the four main headings., International Conference on Planning and Design of Tall Buildings, August 1972, Pennsylvania, USA

In the event of fire in the lower levels of a high-rise building, the upper floors and escape routes can become contaminated with smoke very quickly and in less time than is required to evacuate the building. Control of smoke is therefore an important consideration in the design of buildings.

It is clear that climate has a direct influence on the performance of buildings and nowhere in Canada is this more evident than in the Atlantic Provinces. The Division of Building Research is correlating climatic data with all its building research work and will give special attention to this matter in all its future studies of buildings in this part of the country.

Pressure differences caused by chimney action and the operation of air supply and exhaust systems within a nine- storey office building were measured, for various outside temperatures, across the outside walls and vertical shafts and between floors. These pressure differences depend on the characteristics of air leakage through the building envelope and the interior partitions. Using these measurements, it was possible to determine the height of the neutral zone and the relationship between actual and theoretical pressure differences. If these two factors are known, the pressure differences across the building envelope due to chimney action can be calculated with confidence. The air leakage characteristics of the building envelope were determined by pressurizing the building with a known quantity of air. From these measurements, the amount of excess air required to produce a given pressure withon the building can be found. The air leakage characteristics of the test building indicated that there was a total equivalent leakage area far greater than that assessed for the door and window openings. The amount of excess air required to pressurize individual floors depends also on the resistance to air flow between floors. Pressurization of the first floor of the test building caused only a small increase on the pressure difference across the exterior walls of upper floors, since the separation between the first and second floors was relatively airtight., Presented at the 1966 ASHRAE Semiannual Meeting, Houston, TX, USA, Jan 24-27, 1966