Stress/Strain Distributions and Role of Sheathing in Partition Wall Panels Subjected to Compression

摘要

Built upon a companion study on the load carrying capacity of cold-formed steel wall panels, the stress/strain distributions in each constituent of a panel ― middle and side studs, top and bottom tracks, boards, and screws ― are examined in detail with extensive use of strain gauges. These are subsequently synthesized to analyse the structural performance of the panel as a whole. Panels with 1-side sheathing and one middle stud were tested under vertical compressive loading. The main variables considered are screw spacing (300 mm, 400 mm, or 600 mm) in the middle stud, board type (oriented strand board ― OSB, cement particle board―CPB, or calcium silicate board ― CSB), board number (no sheathing, one-side sheathing, or twoside sheathing), and loading type (1 or 3-point loading). The test results show that, at a given cross-section of the stud, the strains and stresses experienced by the flanges are significantly different from those in the web. Along the vertical direction, the stresses in the stud are not uniform, decreasing as the bottom track is approached. Screw connections between stud and board not only restrain the lateral displacement of the stud, but also support and re-distribute a portion of the machine load to the board and then to the bottom track. The axial forces experienced by the screws are negligibly small during the initial stage of loading, increasing slowly as the load is further increased until substantial stud buckling occurs. Buckling drastically increases the forces acting on a screw, often resulting in its pulling-out from the board and studs/tracks. The results also show that the role of board in a partition wall panel is multi-fold. It acts as a shearing member to steady the whole structure, as a supporting member to enhance the overall and local buckling performance of middle and side studs, and as a structural member to support part of the machine load. It is important account for the contributions of load-sharing boards (via screw connections) when designing cold-formed steel wall panels against minimum weight.