Second Order Inelastic Analysis of Steel Space Frames Subjected to Span Loads

This work provides a new model for the advanced analysis of steel frames subjected to span loads. The proposed model tries to overcome many issues of the analysis. A one element per member concept is used. Large deflection effects are considered by employing fifth order displacement function that takes member lateral loads into consideration. The interaction between the axial force effect and flexural actions is taken into consideration including the actions due to span loads. Plasticity spread along the member span is traced and modeled by monitoring number internal section along the span, then plasticity effects at these sections are merged in the one element stiffness matrix. This model helps to overcome limitations related to one element approach, as most one element models allow nodal loads only, or concentrated plasticity. The accurate representing of plasticity spread in the present model enables the model to take into consideration the variation in fixed end forces due to material yielding. A finite element program is prepared based on the proposed model. Many steel frames are solved and the results are compared with solutions by other researches or by solutions from fine mesh analysis. The proposed model presented high accuracy without much calculation cost.