This thesis is concerned with inferring static, self-equilibrating, axial forces in redundant space frames from knowledge of their natural frequencies and associated mode shapes. Accordingly, it is necessary to have a mathemati cal description of the physical frame in an eigenproblem parameterised with variables accounting for load. Newton's method provides an iterative means of minimising the difference between the eigenvalues and eigenvectors and the measured frequencies and mode shapes they respectively represent forces are thus inferred from the converged eigenproblem. Rather than updating all member forces, models are formulated on force distributions and scalars re lating to the extent of loading form the updating parameters. Enforcing such equilibrium constraints beneficially minimises the order of Newton's method. For multiply redundant frames, it is necessary to formulate the model on a number of force distributions and any state of equilibrium can be described by their linear superposition. The ways in which load affects the dynamic characteristics are investigated thoroughly. Frequencies are shown to coa lesce and exchange places in the spectrum, leading to non-smooth functions since the eigenvalues are numerically ordered. Mode tracing strategies, which utilise eigenvector consistency across coalescence points to conserve function smoothness, are investigated. This consistency, however, is observed to dete riorate if the eigenvalues exhibit veering. Measures facilitating mode tracing when consistency is deficient are explored. Special treatment is required at eigenvalue degeneracy in order to observe eigenpair differentiability, which is necessary for Newton's method. Numerical simulations demonstrate success of force identification in a variety of contexts. Newton's method is effectively applied to identify load in actual, physical frames with single and multiple force distributions. Offset and length parameters supplement load to sta bilise and improve the accuracy of solution. For complicated frames, it is shown that starting iteration in the eigenvector, as well as eigenvalue, neigh bourhood is crucial for convergence to result.

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Since a statistical approach to the wind loading problem was proposed in the early 1960's, there have been a number of gust response approaches developed. However some simplification or approximation employed in those approaches seems to lead to inaccurate predicted results in some circumstances. An improvement of the gust response approach has been attempted in this work. Firstly a flexible mathematical model of natural turbulence characteristics has been suggested as a result of reviewing recent works. Formulae suggested include various parameters which allow the height dependence of power spectral density and co-coherence of the longitudinal turbulence component to be taken into account. For mathematical convenience the height dependence of wind characteristics has been expressed in terms of a power law profile. These height dependent expressions with appropriate parameters have been incorporated with a method for gust response prediction. Secondly the dynamic along-wind force coefficient concept has been employed to improve the conventional stochastic prediction theory for gust response. The coefficient has been evaluated experimentally by using a two-dimensional single degree of freedom system model in a partial boundary layer wind tunnel. Experimental results for the static drag coefficient showed some relevance to previous works. Experimental results for the dynamic along-wind force coefficient have been reduced into an empirical form, with the section aspect ratio and the reduced wind speed as variables, in terms of its ratio to the static drag coefficient. A computer program for the gust response prediction has been developed and convenient chart diagrams have been presented for practical applications. Effects of the variation of parameters used in the wind characteristics' model have been examined numerically and the significant role of the dynamic along-wind force coefficient in the gust response prediction discussed.

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