A.J. Minson

Doctor of Philosophy, Oxford University, Michaelmas 1993

Use of Laser Doppler Anemometer Measurements Near Model Buildings to Determine Wind Loading on Building Attachments

Summary

This thesis firstly reports the use of Laser Doppler Anemometry in an environmental wind tunnel to measure wind velocities near buildings, and secondly the development of an analysis technique, that uses these velocities in summarised form, to determine wind loading on building attachments such as sun-shades, sign-boards and walkways.

Laser Doppler Anemometry has only recently become a practical tool for wind engineers because of developments in miniature probes and signal processing. The Laser Doppler Anemometer (LDA) used for this work, is commercially produced by Dantec Electronic. It measures two orthogonal components using a single miniature probe. The anemometer was used in the 4m x 2m environmental wind tunnel at the University of Oxford. Instantaneous velocities were measured near different building models placed in simulated atmospheric boundary layers.

Since velocity information now available from use of the LDA is more detailed than before, current methods of determining wind loading on building attachments can give better estimates of loading. However they do not make the best possible use of the newly available velocity data. Therefore alternative methods have been investigated.

The quantity of velocity data that can be acquired for a particular location with the LDA is significant. A method that uses all this velocity information will produce the most accurate loading estimates possible. However it is prohibitive to adopt such a method because all the velocity information needs to be stored and be accessible to the design engineer. Alternative methods developed and compared in this thesis, use summarised velocity data in order that it is more easily stored and retrieved, but they do not estimate loading as accurately.

The recommended method best meets the criteria of accurately estimating wind loading using a manageable quantity of velocity data. It uses LDA velocity data summarised into the form of mode and dispersion of maximum speeds in directional sectors and formulae developed from the theory of extreme value analysis, in addition to aerodynamic characteristic data for a building attachment, to determine mode and dispersion of maximum wind loading.

(no thesis available)