Tony Tschanz

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Wind tunnel testing is the only confident method of predicting the response of buildings to natural wind currently available. Modelling techniques are well developed, but rely in most instances on representation of the turbulent boundary layer in a wind tunnel, and complete modelling of all the structural parameters such as shape, mass, damping and stiffness. The resulting dynamic responses of the aeroelastic models can directly be scaled to full scale values. Aeroelastic models, however, are expensive, require much time before availability of results, and are specific to the structural parameters modelled.;The subject of this study is to directly measure the total dynamic modal forces, using a high frequency, balance-model system with a "flat" frequency response. The foam models are mounted on a sensitive, but rigid five-component balance which is described in detail. This balance is believed to represent the state of the art for the intended load ranges.;Practical applications of direct force measurements to estimate the response of structures are presented. Theoretical considerations, and comparisons of results with conventional wind tunnel experiments, show that the method is an economical alternative for many conventional structures. Advantages, in addition to a less costly and time consuming experiment, include the straightforward revisions of predicted responses for modifications to the structure. The modal forces are dependent only on the structure shape and not on its dynamic properties.;Knowing the dynamic force permits structures to be studied for non-linear behaviour. Forces can either be used directly as measured by the balance-model combination, or simulated with a digital computer. Low order auto-regressive processes are shown to give an efficient simulation of most forces. A collection of modal forces with computed parameters are presented, which are suitable for application in the frequency domain (linear problems) or time domain (non-linear problems).;Applications of simulated modal forces is illustrated with studies of simple yielding structures. Simulation studies provide useful information on building behaviour. Only a digital computer is necessary after initial measurements are conducted in a wind tunnel.



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