Abstract
The paper presents research findings on the application of combined plastic mechanism and linear-elastic analyses to estimate the strength of a plain channel steel section subjected to a purely bending moment. In the plastic mechanism analysis, a plastic mechanism model that idealizes an actual failure mechanism model of the investigated section under the purely bending moment is plastically analysed. This analysis is based on the equilibrium between the external energy caused by the rotation of bending moment and the sum of energy dissipated at each plastic hinge of the idealized plastic mechanism model during deformation. From the energy equilibrium analysis, a moment carrying capacity of the section can be expressed in term of its mid-span deflection, which in turn can be used to establish a declining moment-deflection curve. In the linear-elastic analysis that is based on an elastically bending theory, an effective width concept is adopted to account for the effect of local buckling in compressive elements of the section. The utilization of the effective width concept will change section properties and these are used to formulate an elastic relationship of the bending moment and mid-span deflection of the section, which is subsequently shown in the form of an inclining moment-deflection curve. An intersection of the two different moment-deflection curves is assumed to be a theoretical moment capacity of the investigated section. In order to assess the accuracy of using this analytical model, its predicted results are compared to actual ones obtained from bending tests on a number of thin-walled plain channel steel section beams. The comparison indicates that the deviation of individual-predicted data from the experimental one is still scattered within an expected limit of ± 10%. A statistical analysis of the scattered data also shows that its mean value is relatively close to unity with the standard deviation of 0.0393 and this is of course the predicted result as expected.