The shear flexibility of diaphragms consisting of profiled steel sheeting can be calculated by means of the ECCS-Recommendations TC7 TWG 7.5. The main component of the shear flexibility accounts for sheet deformation, which consists of profile distortion c_(1,1) and shear strain c_(1,2). The dominant part c_(1,1) is proportional to K_i. The factor K_i = K_1 applies with fasteners in every trough and K_i = K_2 applies with fasteners in alternate troughs. Both K_1 and K_2 depend on the ratios l/d and h/d of the cross section dimensions d=pitch of the corrugations, h=height of the sheeting profile and l=width of the top flange. For vertical webs K_1 is larger than K_2. This means that larger profile distortion is predicted with fastening in every trough than with fastening in alternate troughs. This is in contradiction to reality. Finite-Element calculations show that the K_2-values given in ECCS-Recommendations TC7 TWG 7.5 are wrong. The correct values for K_2 are given as result of this investigation.
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