Effect of axial deformation on the flexural behavior of one-bay multi-storey building frame

Abstract

Most structural analysts assume in their analysis of multi-storey frames that axial deformations are negligible compared to flexural deformations. The result of this assumption is that such analysts ignore the effects of axial deformation on their analysis by treating both beams and columns as flexural elements. The present study investigated the effect of axial deformation on the flexural behavior of a one-bay multi-storey frame. In adopting the stiffness method for this study, two different element stiffness matrices were used for beam elements and beam-column elements respectively, and Visual BASIC computer program was used in the analysis. The comparison was based on the base moment of the ground floor, which represented the worst condition for design. It was found out that the percentage difference in the base moments increased from 3.4% for four-storey frame to 10.53% for a ten storey frame. This trend implied that the difference in the case of fifty storey frames will be about 51%. It is hereby recommended that columns in frames above three storeys should not be designed as pure flexural members but as beam-columns.

Keywords: Axial deformation, flexural behavior, stiffness matrix, multi-storey frame

International Journal of Natural and Applied Sciences, 5(4): 351-356, 2009