The purpose of this study is to estimate strength of frames against impulsive loads in relation to local strength of ships subjected to wave impact. In particular, discussed is dynamic lateral buckling of thin walled T -shaped beam through the experiments in a pendulum type testing machine by systematically changing geometrical parameters of specimens as well as impact loading conditions. In order to investigate details of dynamic behaviors, the FEM code is also developed, and compared with the experimental results.

INTRODUCTION

It is important to clarify the impact strength of beam for the design of structures. Although we can cite much research work for dynamic strength of structures, few works for dynamic lateral buckling was found except the studies of Goda et.al. (1985, 1986). In the present paper, we discuss on dynamic lateral buckling of the thin-walled beam through the experiments for dynamic lateral buckling and pure bending by changing geometrical parameters of test specimens as well as impact loading conditions. Impact force is applied at the mid-span of flange of the specimen by a pendulum-type testing machine, and measured are impulsive load, bending and lateral deformations, and strains. Static tests are also carried out to compare with dynamic tests, and observed is the second mode of lateral buckling, since lateral deformations are restrained at the mid-span of the specimen. Numerical analysis based on the ordinary FEM procedure, for example, by Kawai (1975) using beam elements is carried out to compare and investigate details of the experiments. This FEM code can take account of collision between the weight and the beam, large deformations due to lateral buckling and material nonlinear effects of plastic deformations and increase of yield stress due to high strain rate. The collision is expressed by a simple model with a spring and a damper, which is the so-called Voigt model.

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