W. Alan DalglieshNational Research Council Canada | NRC · Institute for Research in Construction (IRC)
W. Alan Dalgliesh
M.Eng., P.Eng.
About
115
Publications
23,107
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650
Citations
Introduction
Expertise: Bldg Engineering, Wind Engineering,Glass Strength, and Cladding Durability
Research on: wind effects on high-rise buildings (surface pressures, accelerations, sway); wind pressure on cladding (e.g. pressure-equalized rain screen walls); wind-induced pressures inside buildings; durability of building facades: moisture control; structural design of glass; in-service glass strength and post-breakage behaviour; structural performance of laminated glass and multiply-glazed sealed units.
Additional affiliations
June 1959 - May 1994
Position
- Senior Researcher
Description
- Masonry walls, Wind loads on tall buildings, Strength of glass cladding , Durability of cladding under wind and rain loads. Director of Quality Assurance for a few years before returning to active research.
Publications
Publications (115)
This paper presents some of the background to the new Canadian General Standards Board (CGSB) standard on the structural design of glass for buildings. It also describes strength testing of window glass at the Institute for Research in Construction of the National Research Council of Canada using three different testing machines. Ce document expose...
Although the dangers of damage to roofs from hurricane winds are vaguely appreciated by most people, the nature and distribution of wind forces are not generally understood. The subject is complicated and some understanding of air flow around buildings is required as a basis for sound roof design. It is the purpose of this Digest to assist the read...
Rain penetration through the joints of a building can be prevented by controlling the forces which act to cause it. The main force causing rain penetration is an inward air pressure drop. It can be controlled by maintaining the air pressure of the space behind the wetted outside wall at a level equal to that outside. wind pressure, however, varies...
Cette note fournit aux concepteurs des méthodes pour les aider à se familiariser avec le commentaire B (surcharges dues au vent) du supplément du Code national du bâtiment du Canada, 1980. On devrait lire cette note avec le commentaire B. PRAC
The Commerce Court Tower was the subject of wind tunnel tests in 1969 and in 1977, and the building itself was monitored for various wind effects from 1973 until 1980. The first comparisons of mean and fluctuating pressure coefficients were presented in 1975 and a preliminary assessment of both wind tunnel and building code predictions of tip displ...
In many countries structural design procedures are undergoing changes toward recognition of "limit states", e. g., excessive deformation, unserviceability, collapse. The application of this philosophy has two prerequisites: first, design loads and material properties must be defined on a more realistic (probabilistic) basis; second, design safety r...
Effective moisture control in the building envelope is essential if acceptable service life is to be achieved for the built environment. Effective moisture control implies both minimizing moisture entry into the system, and maximizing the exit of moisture, which does enter, so that no component in the system stays 'too wet' for 'too long'. But what...
Design for moisture control has now become an established part of building envelope design. Hygrothermal modeling tools, capable of simulating moisture transfer in materials, are a key element of the design process. There are three principle methods of moisture transfer in envelopes. They are, in order of magnitude, capillary action, vapour convect...
This paper describes a small study carried out using a hygrothermal simulation tool to investigate the sensitivity of wall performance results to uncertainty in the amount of rain impinging on the wall, Design standards for hygrothermal analysis of proposed designs include methods for selecting appropriate moisture reference years and specify the a...
A building's durability depends on controlling heat and moisture within its envelope. Moisture diffuses through porous materials that may suffer mould growth and decay (if wood-based) when left moist and warm for too long. Designers try to keep vulnerable components dry, but materials can start to deteriorate before reaching the dew point temperatu...
The National Research Council of Canada, with partners from industry, has just completed a four-year project on the wetting and drying performance of exterior walls of low-rise wood-frame buildings exposed to a range of climate loads characteristic of North America. The Moisture Management in Exterior walls (MEWS) project activities included a revi...
Recent history has documented the premature failures of building envelopes in various regions—in North America most notably on the West Coast and the East Coast. The MEWS Consortium, a project undertaken by IRC and its partners, has addressed this issue in detail. The strategy for answering these questions was based on predicting the moisture manag...
The boundary layer wind tunnel (BLWT), which reproduces the increase of wind speed and the propagation of mechanically induced turbulence upwards from the ground, owes its development and validation to measurements of surface pressures, building motions, and other wind effects on full-scale structures. Computational fluid dynamics models are now co...
Premature failures of building envelopes in the 1990s, notably in coastal areas of North America, point to problems with Moisture management by Exterior Wall Systems (MEWS)¹. The MEWS Consortium sought to combine field experience with lab testing and hygrothermal modeling to understand and deal with these problems. The method proposed in this paper...
Premature failures of building envelopes in the 1990s, notably in coastal areas of North America, point to problems with Moisture management by Exterior Wall Systems (MEWS)1. The MEWS Consortium sought to combine field experience with lab testing and hygrothermal modeling to understand and deal with these problems. The method proposed in this paper...
s"- for the purpose of investigating water entry rates into the stud cavity and the drying potential of the wall assemblies under different climate loads. Since the project was a first step in investigating a range of wall hygrothermal responses in a parametric analysis, no field study of building characteristics was performed to confirm inputs suc...
The MEWS (Moisture Management for Exterior Wall Systems) project produced an integrated methodology for assessing the long-term performance of exterior wall systems with regard to moisture management. The methodology includes the integration of information from a review of field practices, extensive measurements of hygrothermal properties of buildi...
The design of exterior walls in a building envelope for optimum moisture management is a challenging task. Many conventional methods or local practice guidelines are available for this purpose, based primarily on regional traditions and with limited performance assessment records. In recent years, new wall systems and unconventional materials have...
By 1997, several field surveys in North America had indicated that rain penetration in exterior walls and poor construction detailing contributed to the shortening of the service life of recently built exterior walls of low-rise buildings in climates with high exterior moisture loads. There was a movement in industry to rethink the ways that exteri...
Task 4 - Environmental Conditions consisted of two main objectives: the first objective was to provide input for the parametric simulation phase of Task 7- Hygrothermal Analysis and the rain penetration test portion of Task 6 - System Performance; the second objective was to develop a method for classifying for US and Canadian climates with respect...
The objective of this report is to communicate, in a very concise form, some of the accomplishments of the MEWS (Moisture Management for Exterior Wall Systems) project. This will be done in terms of the research methodology adopted, as well as the outcome of its application to the first type of walls analysed in the project - Stucco-clad exterior w...
Building damage caused by a moderately strong tornado in the Pilon subdivision of Aylmer, Quebec on Thursday, August 4, 1994 is described. Atmospheric Environment Services classified this tornado as "Force 3" (on a scale of 0 to 5) with winds as high as 270 kmlh. The most severe structural damage observed, however, seems to indicate peak speeds in...
Description
In recent years the design of exterior walls has incorporated more diverse materials and complex building technology than ever before. The use of metal, glass, stone, concrete, and masonry in the building facade challenges architects, engineers, manufacturers, and contractors to better understand materials and systems. STP 1034 reflects...
Wind pressure differences were measured across the rain screen and across the air barrier assembly of precast open rain screen wall panels. Twelve panels were instrumented mostly on the west, north and east walls of the 24th floor of a 27 storey office building in Montreal, U.S.A. The maximum load measured on the rain screen in one year of continuo...
Wind increases the external pressure on windward walls, and decreases it on side and leeward walls. The walls have leakage paths through which air flows either in or out, depending on whether the internal pressure is lower or higher than the external pressure. Internal pressure adjusts to make inflow equal outflow, and depend on the size and locati...
The growing use of glass as a cladding material finds many designers unfamiliar with its structural behaviour, which includes a sensitivity to rate and duration of loading. Prior to 1979, manufacturers' recommended glass thicknesses for any desired area were based almost entirely on the results of previous load tests, but in that year a set of char...
Several years of observations of accelerations during moderate to high wind at the Commerce Court Tower in Toronto, Canada, are presented and the effect of torsion in the upper stories is shown. Model and full-scale observations of the standard deviation of acceration correlate well for most wind directions. Implications for structural design using...
Des révisions importantes ont été apportées au Commentaire B du chapitre 4 du Supplément du Code national du bâtiment du Canada, édition de 1980, en ce qui a trait aux bâtiments de faible hauteur. Ces changements sont le résultat d'une série de mesures prises en vue de rationaliser le calcul des surcharges dues au vent. Ils sont fondés sur des essa...
This note provides background procedures to help designers become familiar with Commentary B.- the 1980 Commentary on Wind Loads, a supplement to the National Building Code of Canada 1980. The note should be read in conjunction with Commentary B. PRAC
Full-scale pressure coefficients obtained from a 57-storey building in Toronto and wind tunnel results from tests in the 9 m by 9 m wind tunnel at the National Research Council of Canada are compared and demonstrate good agreement where sufficient full-scale data exist. A method of treating peak pressures is proposed based on the fit of an exponent...
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 de...
Recent experience with wind-induced glass breakage in high-rise office towers has demonstrated the difficulty of pin-pointing potential problem areas on a building and hence the need for a better understanding of the magnitude and nature of cladding loads.Results of surface wind pressure measurements made simultaneously at 32 points on a 57-storey...
A study is made of the behaviour of ductile (metal) and brittle (glass) panels under dynamic wind loading. The results show that the effect of such factors as dynamic amplification, rate of loading and ductility can generally be neglected. Failure risks implicit in North American codes are compared; some changes in design rules are suggested, inclu...
Design methods based on a statistical approach to the prediction of dynamic effects of wind on frameworks of tall buildings are steadily gaining acceptance. Similar concepts can be applied to wind loads on cladding, although there are important differences such as exposure, size, and dynamic properties of the elements considered. Wind pressures and...
Wind pressure measurements made over a 4-year period on a 34- story building in downtown Montreal were used to obtain data for checking and improving wind tunnel techniques of modelling flow characteristics of wind and aerodynamic behaviour of buildings. Comparisons with model measurements are made on the basis of mean pressures, rms pressures, pow...
Design details often lack tolerances, causing problems in construction. Though standards and codes may supply them, tolerances are uncoordinated from trade to trade, and are usually neither mandatory nor enforceable. Designers should allow for them, but to do so rationally, must know what variations occur in practice. This information is often not...
Two standards widely used in North America for strength design of architectural glass rely on a failure prediction model (FPM) that has been fitted to data from tests to failure of full-sized rectangular plates under uniform load. For non-rectangular units or non-uniform loads, however, rational analysis and limiting tensile stress or engineering a...
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 gath...
This paper describes a method for simulating the natural wind boundary layer in a conventional, short working section, aeronautical wind tunnel. The boundary layers, which may be as thick as one-half of the working section height, are generated by spires at the working section inlet. This approach has been used to measure mean wind pressures and pr...
The use of a standard one-turn potentiometer to measure wind direction can create a problem because of the discontinuity in the potentiometer signal when the sliding contact passes from the maximum output level across the gap to the lowest output level, or vice versa. This results in an error in the calculation of the mean. This Note discusses a me...
The objective of this report is to communicate, in a very concise form, some of the accomplishments of the MEWS (Moisture Management for Exterior Wall Systems) project. This will be done in terms of the research methodology adopted, as well as the outcome of its application to the first type of walls analysed in the project - Stucco-clad exterior w...
Uncontrolled moisture accumulation in the building envelope reduces the structural integrity of components through mechanical, chemical and biological degradation. Damage induced by moisture includes rotting of wood studs and other wood-based products, efflorescence and spalling of masonry systems, and rusting of wall fasteners. Also, excessive moi...
Premature failures of building envelopes in some North American locations appear to be climate related. An IRC-led research consortium called MEWS (Moisture Management of Exterior Wall Systems) developed a method using hygrothermal modelling to identify locations where walls may experience moisture related problems. The method classifies climates b...
Les toits des maisons sont exposés au danger d'endommagement lorsque le vent souffle avec une violence d'ouragan. La plupart des personnes ont une notion vague de ce fait, mais ignorent la nature et le réparition des forces engendrées par le vent. La question est complexe; une étude correcte de toit doit cependant reposer sur une connaissance suffi...
Task 4 - Environmental Conditions consisted of two main objectives: the first objective was to provide input for the parametric simulation phase of Task 7- Hygrothermal Analysis and the rain penetration test portion of Task 6 - System Performance; the second objective was to develop a method for classifying for US and Canadian climates with respect...
One approach to controlling rain penetration into walls is to design them using the pressure-equalized rain screen principle. This design minimizes the wind pressure difference across the exterior cladding (rain screen), thus reducing the predominant force that drives rain into the wall. A pressure-equalized rain screen wall is essentially a cavity...
This paper describes the philosophy and formulation of the simple and detailed procedures for wind loading of the NBC 1970. Predictions of dynamic drag response and cladding pressures are compared with full scale measurements on several tall buildings. It is concluded that the predictions of drag response and windward pressure are satisfactory. Are...
