EFFECTS OF CROSS-RAILS ON STEEL SHEET SHEAR WALLS WITH BURRING HOLES

Shear stiffness and large deformation behavior

Abstract

 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-high-walls is 2.73-m-long × 0.455-m-wide × 1.2mm-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. 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. The effects of cross-rails which are designed to strengthen the bearing capacities of the studs, on the shear walls were clarified by experiments and analyses.

 Shear stiffness of the wall was gradually decreasing according to the deformation increasing of the wall, even in the elastic region, regardless of cross-rails. 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. Ultimate strength of the wall depended on tension fields restrained by cross-rails.

 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 cross-rails. 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 studs restrained by cross-rails. The effect of cross-rails maintained wall strength stable in inelastic region. The tension in the interval between the burring holes was balanced with the compression resisted by burring holes and horizontal shear forces at screw connections created by studs and cross-rails. The design formula to evaluate the shear strength of the wall at a story angle of 1/200 to 1/100 was developed and the values obtained using the formula lie almost the same values obtained through experiments.