Lateral Resistance Of Steel Clad Wood Framed Shear Walls With Openings PDF Download

"To enter into the construction market for mid-rise buildings, e.g. 5 to 8 storeys, the cold-formed steel (CFS) industry requires a solution to address the need to resist higher seismic shear forces. The proven performance of steel-sheathed shear walls is required to compete with hot-rolled steel lateral framing shear wall systems; i.e. all-steel shear wall configurations capable of carrying lateral loads in excess of 60 kN/m (4170 lb/ft). The American Iron and Steel Institute (AISI) developed a design standard for cold-formed steel lateral framing systems, i.e. the AISI S400-15. This standard contains design information for shear walls with shear resistance values up to 30 kN/m (2085 lb/ft). Various solutions exist to increase the shear resistance of a CFS framed shear wall to a level appropriate for mid-rise buildings. For example, in shear walls with sheathing placed on both sides of the wall, torsional loading on the framing members was avoided, and hence the shear resistance was significantly increased. However, the ductility of the walls was not improved compared to previously run tests due to the sheathing pulling over the screw fasteners.A configuration in which the sheathing is placed at the mid-line of the framing, denoted the “centre-sheathed” shear wall, was recently developed through a laboratory test program. These walls were configured to centrally confine the sheathing within the framing, which resulted in the removal of torsional forces on the chord studs and provided for a substantial increase in both shear resistance and ductility in comparison with walls having external sheathing on both sides. The initial test walls proved to have higher shear resistance, i.e. over four times that currently found in the AISI S400-15, and could maintain this resistance to drifts exceeding 6%. However, the high shear forces posed difficulties in designing the perimeter framing members and attachments to the foundation given that the structure is composed of CFS with a maximum thickness of 2.5 mm. This second laboratory-based study was conducted to configure centre-sheathed walls to attain intermediate shear resistances but maintain the ability to carry load at high drift levels. In addition, tests were carried out on the bare frame structure to identify the added shear capacity provided by the specially detailed CFS perimeter frame. Further, connection tests were completed to address the need to develop bearing design equations for the double shear 3-ply screw connections that connect the sheathing to the frame, which is not currently addressed in any design standard on cold-formed steel"--