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TW Catalogue EN Int. 03-2015

2703/2015 11 5/6 Basic information on the design aid The basic principles of calculation in the foregoing design aid are explained below. This information can also be used to calculate coupling points with other roof pitch angles. Screw forces Screw 1 is always decisive, i.e. the maximum loading of the coupling point is reached when the tensile force in screw 1 is equal to its load-bearing capacity. Arrangement Remarks – Longitudinal forces in linked rafters (e.g. in roof structures) cannot be transferred with this coupling point layout. – Appropriate action must be taken to ensure that the angle of insertion is maintained. – All calculations must be verified and signed off by the planner in charge before the work is performed. Verification In the event that a combination of loads arising from loads acting only vertically is applicable, i.e. K acts vertically, the following applie Kz = K · cos () Ky = K · sin () α Kz Ky Ky K Kz K=Kv Lot F1,d nef · FRd <_ 1 with kmod · FRk M FRd = oder <_ 1 Kz,d + Ky,d 2 · nef · FRd Proofs for this instance can therefore also be written as follows cos () + sin () 2 · nef · FRd Kd · <_ 1 The verification equation in the case of vertical loading is therefore as follows with FK,Rd = Kd FK,Rd <_ 1 nef = n0,9 factor for taking the effectiveness of the fasteners into account nef = 1,0 for a pair of screws nef = 1,87 for two pairs of screws nef = 2,69 for three pairs of screws Fax,Rk characteristic pull-out resistance (see table page 6) The screws are always arranged to that they cross at half rafter height in the shearing plane between the two rafters. see table page 4 Kz Ky Ky, Kz: coupling force in the y and z directions F1, F2: resulting forces in the screws The screw forces are the product of: Kz + Ky 2 F1 = (positive tension, negative compression) Kz – Ky 2 F2 = Combinations The following values are listed in the load-bearing capacity tables 2 · nef · Fax,Rk cos () + sin () F1,Rk = WT Joining timber raftersTechnical documentation and data sheets 11.11.

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