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This paper presents a numerical analysis of large displacement responses of elastic-plastic plane frames under static and dynamic loads, by applying the vector-form intrinsic finite element method. The VFIFE method defines the structure into a number of mass points, and applies Newton's second law and the internal force equilibrium to describe the motions of each mass point. By tracing the motions of all the mass points, it can analyze the large geometrical and material nonlinear changes during the motion of the structure without using the geometrical stiffness matrix and iterative procedures. Three different numerical examples are presented to demonstrate both the capability and the accuracy of the VFIFE method in a nonlinear dynamic analysis of frame structures with extremely large displacement.CR formulation based on a convected material frame. All of these methods are rather effective for analyzing the transient responses of structures made of inelastic materials and large deformation characteristics [9]. For nonlinear material structures, most of the existing nonlinear material models can be classified into two main categories: lumped and distributed plasticity models. The lumped model is an efficient way to represent inelasticity in frames. A typical finite element method (FEM) considering the geometrical and material nonlinearities requires iterations at each incremental step to achieve the equilibrium [10]. This method encourages flexural yielding and can ensure that plastic hinge rotation will occur at the member ends rather than along the column length. The second-order plastic hinge concept based on the use of stability interpolation functions has been proposed for frame structure analysis [11][12][13][14][15][16][17]. Marante et al. [18] proposed a general criterion of localization and two plastic hinges at the end of the frame member. Some researches improved the lumped plastic hinge method, such as for example the distributed plasticity model (also called plastic-zone model), which allows for the gradual spread of yielding within the member. In the distributed plasticity model, the frame element stiffness can be computed by using either the displacement [19] or the force-based approach [20][21][22]. This allows plastic hinges to form at any location in an element. In addition, the element cross-section can be a fiber section using different stressstrain models for different fibers within the cross-section. Without properly taking into account the internal forces due to pure deformations, most of these studies may not be able to simulate inelastic structural responses of moving structures subjected to extremely large displacements or deformations.Another type of method, the discrete numerical method is suitable to study large deformation, cracking and failure of structures. For example, the rigid-body spring model (RBSM) was proposed by Kawai and Kondou [23]. In this model, each element consists of rigid bodies with two springs, called normal and shear springs which allow the restoring forces to be ...

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