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TW Catalogue EN Int. 03-2015

36 03/2015 11 WT / WR Dowelled purlins 2/5 Remarks – The calculation process is an approximation, i.e. it is only suitable for preliminary design calculations. – The fasteners must be arranged so that half their length is in each structural component. – Spacing e can be adjusted in accordance with the shearing load curve. – If there is a layer of board between the purlins, this can be regarded for simplicity’s sake as having no structural effect. However, it must be ensured that there is no gap between the board and the purlins, so that the compression component can be absorbed without deformation. – All calculations must be verified and signed off by the planner in charge before the work is performed. Proposal of design Cross-section values The following calculation method is an approximate calculation for dowelled purlins derived from two to three identical cross-sections. Coefficients of diminution Structure of the purlin Moment of resistance  Moment of inertia  two-parts 0,85 0,65 three-parts 0,60 0,33 Source: SIA Standard 265 Spannungen: 12 b σef τef hh Fuge 1010 >> 5d5d >> 5d5d >> 5d5d >3d>3d>>5d5d>3d>3d ee ee ee D t 45 t 45° hhhh l/2l/2 l/2l/2 Design h = hi hges =  hi Wy,ef =  · Wy,starr =  · h² ges · b/6 Iy,ef =  · Iy,starr =  · h³ ges · b/12 e < eerf = 2 · hges · Fv,Rd 3 · Vd 2-part cross-section e <_ eerf = 3 · hges · Fv,Rd 4 · Vd 3-part cross-section e selected distance between fasteners eerf required maximum distance between fasteners h = hi height of a part cross-section hi > hmin = hges height of the total cross-section l length of selected fastener Vd calculated shearing force Fv,Rd characteristic shearing load-bearing capacity of a fastener (s. table on page 4 and 5) F1,Rk Pull-out resistance from timber F2,Rk Tensile load-bearing capacity of the fastener The coefficients of diminution take into account the flexibility of the fastener in the shearing joint. Dowelling is designed on the assumption of a rigid joint. l (2·2) Stresses: Joint Fv,Rd = F1,Rk · kmod M M = 1,3 M (GL)= 1,25 WT-T Fv,Rd = min M1 =1,3 M2 =1,3 F1,Rk . kmod M1 F2,Rk M2 ( ) WR-T M1 (GL)=1,25 Technical documentation and data sheets 11.11. 3603/2015 two-parts 0,850,65 three-parts 0,600,33

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