Masashi Iura

Experimental and numerical study on cyclic behaviour of steel beam-to-column joints

Ten specimens are tested to investigate the cyclic behavior of beam-to-column joints of steel frames with joint panels. The performances of the joints with respect to strength, rigidity, and hysteretic performance are examined. Three different load-carrying mechanisms can be identified. Panel resistance ratio (Rp) is presented for predicting the buckling patterns. The validity ofRp is confirmed through the present experimental results. On the basis of the experimental results of steel beam-to-column moment joints, 3-D nonlinear finite element models are established to analyze the mechanical properties of these connections. The load-displacement curves of the finite element analysis are in good agreement with those of the tests in terms of strength and unloading stiffness. A shear lag phenomenon was captured in the beam flanges by not only experimental results but also numerical analysis. Parametric studies are conducted on the connections under monotonic loading to investigate the influences of connection dimension, resistance ratio on the connection behavior. It was found that the failure modes are influenced by the resistance ratio, while the thickness of joint panels resulting in large effects on the strength and stiffness under shear failure mode.

A generalized variational principle for thin elastic shells with finite rotations

Abstract Entirely Lagrangian nonlinear theory of thin elastic shells with finite rotations is developed. Without restriction to small strains, accurate equilibrium equations and boundary conditions are derived, utilizing the modified irrational tensor of change of curvature. The introduction of variations of displacement vectors in place of variations of displacement components makes it possible to reduce computational efforts for deriving the shell equations. With the aid of the present shell equations, the Hu-Washizu variational functional including the effects of finite rotations at the shell boundary is generated.

Flexible translational joint analysis by meshless method

Element free Galerkin method (EFGM) is used to analyze a flexible translational joint. A moving constraint condition is a major concern for the translational joint analysis. It is shown that the EFGM is well suited for an analysis of flexible translational joint. Original shape function in the EFGM is modified so that essential boundary conditions are imposed by the same way as that of finite element method (FEM). The modified shape function possesses physical values at both ends of the element. The completeness of the modified shape function is discussed. Employing the present modified shape function makes easy to implement the moving constraint condition. Numerical examples for a static cantilever beam are presented for a comparison between the penalty method, the Lagrange multiplier method and the present one. As second example, a large deformation problem is solved for a comparison between the FEM and the EFGM. Finally, a simulation of flexible translational joint is shown.

Variational Integrators for Dissipative Systems With One Degree of Freedom

Variational integrators are developed for dissipative systems with one degree of freedom. The dissipation considered herein is of simple Rayleigh dissipation type. The present formulation is based not on the Lagrange-d’Alembert principle, but on Hamilton’s principle. A benefit for using variational integration techniques is stressed in this paper. The discrete algorithms are obtained by a stationary condition of action integral, in which the Lagrangian is directly discretized. Unlike the existing algorithms, a coupling term between mass and dissipation exists in the present algorithms. A mixed method, in which a velocity is independent on a position coordinate, is presented for dissipative systems. In order to investigate an accuracy of numerical integrators, we introduce a new parameter in addition to the energy decay. Numerical examples show that the present variational, integrators are available for not only highly but also weakly dissipative systems.Copyright

Accuracy of Corotational Formulation for Timoshenko’s Beam under Finite Displacements

On the basis of the polar decomposition theorem, the relative deformation is described by using the moving coordinate system, referred to as the corotational formulation. The use of the corotational formulation is motivated by the assumption of small strains in the beam. In spite of using the small-strain assumption, satisfactory numerical results have been obtained with increasing the number of elements. Goto, Hasegawa and Nishino [1] and Iura [2] have discussed the accuracy of finite element solutions for Bernoulli-Euler’s beam. Iura [2] has pointed out that even if the linear theory is used for describing the relative deformation, the numerical solutions obtained converge to the solutions of the finite-strain beam theory with increasing the number of elements. In the case of Timoshenko’s beam, however, there has been few studies for the accuracy of finite element solutions.