The Alan G. Davenport Wind Loading Chain

Alan G. Davenport Wind Load Chain

By Nicholas Isyumov | June 20, 2013

The technical and scientific communities celebrate their greatest sons by attaching their names to their outstanding works. This distinction honors achievement and serves as a reminder and inspiration for future generations. References to such achievers are particularly abundant in wind engineering, which is a blend of meteorology, fluid mechanics, aerodynamics, structural engineering, structural dynamics, statistics and probability theory.

Its technical terminology is studded with famous names attached to important ideas and concepts. These include such important non-dimensional quantities as the Richardson, Rossby, Reynolds, Mach, Jensen, Cauchy, Froude, Keulegan-Carpenter; Strouhal, Scruton and Tachikawa numbers; the Monin-Obukhov stability parameter; the Coriolis parameter; the Bernoulli, Euler and Navier-Stokes equations; the Prandtl mixing length; Taylor’s statistical theory of turbulence; the Kolmogoroff’s inertial sub-range; the Beaufort, Saffir-Simpson and Fujita scales of wind speed; the Gaussian, Poisson, Raleigh, Weibull and Gumbel statistical distributions; Lieblein’s method of fitting extreme values; Rice’s up-crossings rate; the Helmholtz resonator;  the Raleigh method for determining natural frequencies of structures; and many others.  

Honouring Alan G. Davenport      

On July 12, 2011 during 13th International Conference for Wind Engineering (ICWE-13) in Amsterdam, the General Assembly of the International Association of Wind Engineering (IAWE) unanimously added the “Alan G. Davenport Wind Loading Chain” to the wind engineering terminology.This describes Alan Davenport’s approach to the evaluation of wind loads and wind-induced responses for buildings and structures. Many engineers remember Alan G. Davenport’s name in connection with specific aspects of wind engineering.These include his power law wind profiles; his spectrum of turbulence; his admittance and joint acceptance functions, which describe the spatial and temporal properties of turbulence as required in the evaluation of dynamic wind action; his gust effect factor; his pioneering use of wind tunnel model studies to chart the dynamic properties of buildings and structures; his statistical methods for predicting maximum values of extreme winds and their effects of wind on buildings and structures; and his criteria for judging the acceptability of the wind-induced effects.

Notwithstanding, the importance of these individual contributions, Professor Davenport’s greatest legacy is his rational approach or “chain of thought” for evaluating the action of wind. His wind loading “chain” is described as follows: 

Alan G. Davenport Wind Load Chain Graphic

Central to Professor Davenport’s method for determining the action of wind is the equation which relates the wind loading on a particular building or structure to the combined effects of the local wind climate, which must be described in statistical terms; the local wind exposure, which is determined by the terrain roughness and topography; the aerodynamic characteristics of the building shape; and the potential for load increases due to possible wind-induced resonant vibrations.

His wind loading chain also requires that clear criteria must be put in place in order to  judge the acceptability of the predicted wind action. The effects of wind on the integrity of the structural system and the exterior envelope are foremost concerns. Serviceability considerations, such as the wind-induced drift and the effects of wind-induced motion on occupant perception and comfort are also important. Not to be overlooked are the effects of wind on pedestrians in outdoor areas.

In his papers Alan referred to this entire process as the wind loading chain. This was in recognition that the evaluation of wind loading and its effects relies on several interconnected considerations, each of which requires scrutiny and careful assessment. With analogy to a physical chain, the weakest link or component of the process determines the final outcome. Little is gained by embellishing strong links but much is lost by not paying attention to the weak ones. It is most fitting that the IAWE chose to posthumously honor Professor Alan G. Davenport by adding the “Alan G. Davenport Wind Loading Chain” to the wind engineering terminology. This was done in recognition of Alan’s many contributions to the development of wind engineering and with the expectation that the use of this terminology to describe Alan’s approach to the wind loading process will keep both the man and his works in our memory. The introduction of this new terminology bestows honour on faculty, staff and students who had the opportunity to interact with the late Professor Davenport. Also, it adds distinction to the Laboratory which he founded, the Faculty of Engineering of which he was a member and to Western University.    

About the Author
Nicholas Isyumov is a Consulting Director and Former Professor and Research Director at Western's Boundary Layer Wind Tunnel Laboratory.