| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 2000: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1999: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
When moment resisting steel frames are subjected to severe earthquake, high shear stress occurs in the panel zones of column-to-beam connections. The shear deformation of panel zones may induce secondary stress into the beam flange at the connection, and may cause the brittle fractures at the beam end In this study, loading tests were carried out to investigate the effects of the shear deformation of panel zones on the beam flexural behavior. Further, for the purpose of examining the strain distribution at the connection, numerical elasto-plastic analyses were carried out by using the finite element program. The Mowing conclusions can be made :
1. The shear deformation of panel zones induces secondary stress into the beam flange at the connection, and increases the strain concentration at the beam flange.
2. If the fracture toughness of the beam flange material is high, the brittle fracture of the beam flange cannot occur in early stage. So, the shear yielding of the panel zone can relieve the amount of plastic deformation that must be accommodated in the beam. As the result, the deformation capacity of frames increases as the panel to beam strength ratio decreases.
3. In the case of the beam flange with low fracture toughness, the brittle fracture of the beam flange occurred, even if the panel to beam strength ratio was 0.85. In these tests, the fracture mode (ductile or brittle) depends on the test temperature rather than the panel to beam strength ratio. Therefore, although the panel yielding precedes the beam yielding, it is necessary to avoid the use of the beam flange with low fracture toughness, or to improve the connection detail in order to keep out the occurrence of shear cracks.
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