SHEAR RESISTANCE MECHANISMS OF STEEL SHEET WALLS WITH BURRING HOLES: Shear stiffness and large deformation behavior

Shear walls in which sheets with burring holes aligned along the vertical direction are fastened to frame members, are applied to multi-story buildings in seismically active regions. A sheet for the standard 2.73-m-high-walls is 2.73-m-long × 0.455-m-wide × 1.0-mm- or 1.2-mm-thickness with seven cold-formed burring holes with the diameter of 200mm, which are created by cold pressing a sheet with small-radius holes. A burring hole contains rib (curvature radius: 10mm and 5mm height cylinder) to make edge-stiffened circular hole. A configuration with burrs on the inside and smooth on the outside enables the construction of omitting the machining of holes for equipment and thinner walls of simplified attachments of finishing. In-plane shear experiments and finite element analyses revealed that the walls that receive the in-plane shear force allow shear stress to concentrate in intervals between the burring holes. The walls changed from the elastic to plastic region and maintained stable strength. The walls at 1/300 story angle had stress concentrations at the intervals between the holes. The walls at 1/100 story angle experienced out-of-plane deformation at the all intervals simultaneously. The deformations were limited in the intervals and a large out-of-plane waveform in a sheet was effectively prevented owing to the ring-shaped ribs of the holes. Shear stiffness of the wall was gradually decreasing according to the deformation increasing of the wall, even in the elastic region. The burrs of steel sheets on the one side of the sheets created the asymmetry and the directions of principal stress flows on the sheets varied in three dimensions. Therefor out of plane deformations occurred on the sheets and inclined tension fields occurred in the intervals between the burring holes like post shear buckling behavior that Dr. Basler proposed for plate-girder designs. In this paper, new design methods are proposed for evaluating the stiffness of the walls using the idea of decreasing the band-width of the inclined tension fields with the effect of the thickness of the steel sheets. The design formula to evaluate the shear strength of the wall at a story angle of 0 to 1/200 was developed and the values obtained using the formula lie almost the same values obtained through experiments. The large deformation behavior was also depended on the tension fields on the intervals between the holes. The shear strength at a story angle of 1/200 to 1/100 was increased by the stu