This thesis presents an approximate method for analysis of dense spaceframes. The approach is based on transforming a dense spaceframe into a similar structure with lower density. The reduced structure is analysed in the usual manner and the results are employed to obtain an approximation to the behaviour of the actual structure. To assess the accuracy and limitations of the proposed method, a number of practical examples are analysed. The influence of irregularity of loading and support conditions have also been investigated. A comparison of the results obtained by the method with those obtained by the exact analysis has shown that the accuracy of the method is satisfactory for design purposes. In generating data and organising graphical output for the examples, the concept of formex algebra together with its programming language Formian have been utilised. The application of the method has been extended to composite spaceframes, consisting of skeleton double layer grids combined with concrete slabs. The proposed method is a natural engineering approach. It preserves almost all the particulars of the original structure but allows the analysis to be performed with much smaller systems of simultaneous equations. The method has the potential of being extended in many directions for analysis of other space structures. Also, it would be of interest to extend the idea to the dynamic response calculations and non-linear analysis of spaceframes.