Elastic And Plastic Analysis Of Flexural Bracing-Frame

This paper presents an analysis of the elastic-plastic stability of frames braced by flexural bracings. Because of the inherent complexity of the problem, a simplified model is used in the present paper in which the frame is replaced by a leaning column and the flexural bracing is modeled as a vertical column. Horizontal forces and vertical loads are exerted on the system, and equations for determining the required cross-sectional rigidity of the cantilever columns are established. It is found that the required cross-sectional rigidity under combined actions of horizontal loads and vertical loads is greater than the summation of the required rigidities under horizontal loads and vertical loads separately.A notional load for flexural bracing frames is proposed to avoid in the design of steel structures to determine the effective length of columns. Notional loads are applied on the frame stories, with second-order elastic analysis, considering the material nonlinearity, residual stress and initial geometric imperfections, flexural bracing frame model under variety of geometry and load conditions and a series of the ultimate bearing capacity are analyzed, and then the notional load coefficient and the approximate formula of the notional load are proposed. It is found that the results with finite element results are in good agreement no matter with or without horizontal load, and no matter cross-section or variable cross-section.