Constitutive Model of a Steel Strip subjected to Oscillatory Deformation with Buckling and its Ultimate Anti-Earthquake Strength

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 12650468
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 構造工学・地震工学
• Research Institution: TOHOKU UNIVERSITY
• Principal Investigator: IWAKUMA Tetsuo Tohoku University, Graduate School of Eng., Professor, 大学院・工学研究科, 教授 (60120812)
• Co-Investigator(Kenkyū-buntansha): GOTO Fumihiko Tohoku University, Graduate School of Eng., Research Associate, 大学院・工学研究科, 助手 (10261596)
• Project Period (FY): 2000 – 2002
• Keywords: Localization / Cyclic Loading / Elasto-Plasticity / Non-Coaxiality / Finite Element Method / Instability

Research Abstract

Behavior of a steel strip subjected to a model of earthquake vibration associated with buckling has been experimentally investigated to order to gather knowledge to create a new macroscopic constitutive law of such a strip under earthquake motions. The basic test results show that the toughness of the strip is likely to be reduced by experiences of plastic large deformation with buckling especially by many-cycle patterns of loadings.
While it has not been observed clearly, the macroscopic rigidity of the strip toward its tensile environment after the buckling is much smaller then the elastic stiffness but is much larger than the plastic hardening coefficient. This behavior in considered to occur during straightening of the buckled strip, and is not taken into account by a design using the so-called skeleton curves.
Furthermore, when the first cycle of loading buckles the strip as a loading model of the strong earthquake motion near or right above its epicenter, areas of the succeeding oscillatory loops due to the cyclic loadings with the same amplitude are rather largely diminished in comparison with those observed in standard cyclic loadings. This phenomenon may warn the method of design using the skeleton curves, because such curves are usually constructed under the standard loadings.
Of course, the skeleton curve may be useful in designing point of view. But our experiments show that further adjustment of constitutive laws may be required. Unfortunately comparison of the experimental results with numerical model cannot be carried out because of shortage of the number of experiments. We will continue similar tests, but we may change the purpose of the tests;i.e. such behavior of plastic large deformation with buckling may be useful to design a new device against fall-offs of bridge structures.