CAD-supported preliminary column force calculations in multi-storey buildings
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006.
The predominately manual, time-consuming and error-prone procedure currently used in engineering offices for the calculation of preliminary column forces in multi-storey buildings constitutes the motive for the research described in this study. Identifying the current procedure as in need of improvement, techniques and prototype software posing a semi-automated alternative, are developed. Influence areas used for load-assignment are established with the use of a Voronoi diagram calculated for a specific floor geometry. The forces transferred to the columns are based solely on the size of the influence areas thus calculated. The definition of the floor geometry, as well as the definition of loads and other necessary input parameters, are performed in a CAD-system, into which the Voronoi functionality is integrated. The accuracy of the forces obtained with the implemented procedure and, consequently, the accuracy of the forces as they are calculated in current practice, is determined through comparison with the results of finite element analyses. The comparative analysis of a sample of typical floor geometries allows an evaluation of the results and the identification of tendencies observed regarding the errors obtained. It is concluded that calculating column forces based on influence areas, i.e. solving a geometrical problem without taking any stiffness properties into account, is unsafe. The implication hereof is twofold. Firstly, it serves as a warning concerning the technique currently used in practice and secondly, it steers the investigation in the direction of a finite element analysis: using the influence areas as a basis for automatic meshing, a semi-automated analysis can be performed relatively inexpensively, using plate elements.