A NONLINEAR ANALYSIS METHOD OF STEEL FRAMES USING ELEMENT WITH INTERNAL PLASTIC HINGE

A nonlinear analysis method of steel frames using element with internal plastic hinge is proposed. This method can analyze the frame member applied with laterally-distributed loads only using one element even that a plastic hinge appears within the member. By dividing the member into two segments at the location of the maximum moment, the incremental stiffness matrix of the two segments from time t to t + dt are derived, then the beam element stiffness equation with internal plastic hinge after the static condensation can be obtained. What's more, this method also considers the influences of some geometrical and material nonlinear factors including second-order effect of axial forces, shear deformation, cross-sectional plastification, residual stress and initial imperfection. This method not only overcomes the time-consuming disadvantages of plastic zone method of frame members because of the fine mesh discretization but also makes up for the problem of the traditional plastic hinge element that plastic hinges must form at the elemental ends. Analysis results show that the proposed method is satisfactory.