Cyclic behavior of beam-column joints with various yielding modes

Abstract This paper discusses the yielding mode of a beam-column joint and proposes a mode classification system. The yielding mode can be classified into six categories, including panel yielding, panel yielding dominated, beam yielding, beam yielding dominated, column yielding, and column yielding dominated. The mode can be determined by the column-to-panel strength ratio and the beam-to-panel strength ratio. Four beam-column joint specimens composed of wide-flange beams and square tube columns were tested. Two specimens were subjected to a high axial force, and the other two were not. The specimens were originally designed with various yielding modes. However, due to the unexpected high yield strength of the steel, the calculated strength ratio indicated that all specimens would exhibit the panel yielding dominated mode. Experimental results showed that the panels of all specimens dissipated the most energy, which is consistent with the characteristics of the panel yielding dominated mode. Despite exhibiting this mode, specimens that were subjected to high axial forces eventually failed by local buckling of the column. Moreover, one of the beam-column joint specimens developed severe column-to-diaphragm weld fractures, although the column had very small rotation. Finite element (FE) analysis was conducted on a series of beam-column joints with various strength ratios and a typical plane steel moment frame, and this approach also verified the concept of yielding mode classification. The FE analysis results indicated that the unexpected column-to-diaphragm weld fracture in one specimen resulted from the out-of-plane deformation of the extended diaphragm.