ADVANCED ANALYSIS OF STEEL FRAMES USING ELEMENT WITH INTERNAL PLASTIC HINGE BASED ON SECTION ASSEMBLAGE CONCEPT AND SECTION SPRING STIFFNESS

The yield function of an I or H section is derived by using the section assemblage concept, and an advanced analysis method of steel frames is proposed by assuming a spring with zero-length at the end and inner part of an element to consider the cross-sectional stiffness. It is demonstrated that the plastic hinge at the inner part of the element can be well predicted, based on the proposed method, by only using one element for the members subjected to distributed loads. The proposed element has the same nodal degree of freedom as a conventional element by condensing the non-nodal degree of freedom introduced in the derivation. In the proposed method, the stability function is used to consider the shear deformation and geometric nonlinearity, and the residual stress is considered in the initial yield function. Also, the reduced tangent modulus method is used to consider the influence of initial imperfections. Numerical analysis shows that the proposed method has a high accuracy and efficiency.