Sheet-to-purlin fasteners arrangement and the value of rotational restraint of cold-formed Z-purlins

The method of fastening the trapezoidal sheeting to the supporting beams has a significant influence on their rotational restraint, and thus their buckling resistance. Commonly one fastener is placed in each trough of the sheeting. In this paper the arrangement of two fasteners located near the trapezoidal sheeting webs in every second trough was investigated. Such an arrangement, with the same number of fasteners along the purlin, increases the value of the rotational stiffness CD and in a consequence favorably affects the bending resistance of cold-formed Z-purlins. Such conclusions were based on the results from 28 experimental tests and the results from the corresponding numerical models built in the Abaqus software. The numerical investigation was also extended to the additional 8 models, which had not been tested experimentally. Finally, the buckling resistance of cold-formed Z-purlins restraint by the trapezoidal sheeting, according to Eurocode 3-1-3, for two of the most encountered static schemes of purlin were calculated with the use of rotational stiffness CD values obtained for two arrangements of the sheet-to-purlin fasteners.