IEC 61400-1 pdf download

IEC 61400-1 pdf download.Wind turbines – Part 1: Design requirements
The approach in 7.6.1 .1 , where the partial safety factor for loads is applied to the load response, assumes that a proper representation of the dynamic response is of prime concern. For foundations or where a proper representation of non-linear material behaviour or geometrical non-linearities or both are of primary concern, the design load response S d shall be obtained from a structural analysis for the combination of the design loads F d , where the design load is obtained by multiplication of the characteristic loads F k by the specified partial load factor γ f for favourable and unfavourable loads,The load responses in the tower at the interface (shear forces and bending moments) factored with γ f from Table 3 shall be applied as boundary conditions. For gravity foundations, the limit states considering overall stability (rigid body motion with no failure in soil) and bearing capacity of soil and foundation shall be regarded and calculated according to a recognized standard. In general, a partial safety factor of γ f = 1 ,1 for unfavourable permanent loads and γ f = 0,9 for favourable permanent loads shall be applied for foundation load, backfilling and buoyancy. If it can be demonstrated by respective quality management and surveillance that the foundation material densities specified in the design documentation are met on site, a partial safety factor for permanent foundation load γ f = 1 ,0 can be used for the limit states regarding bearing capacity of soil and foundation. If buoyancy is calculated equal to a terrain water level, a partial safety factor for buoyancy γ f = 1 ,0 can be applied. Alternatively, the check of capacity of soil and foundation can be based on a partial safety factor γ f = 1 ,0 for both favourable and unfavourable permanent loads and the check of overall stability can be based on a partial safety factor of γ f = 1 ,1 for unfavourable permanent loads and γ f = 0,9 for favourable permanent loads, using in all cases conservative estimates of weights or densities defined as 5 % / 95 % fractiles. The lower fractile is to be used when the load is favourable. Otherwise, the upper fractile is to be used.7.6.5 Critical deflection analysis Replace the existing text by the following new text: 7.6.5.1 General It shall be verified that no deflections affecting structural integrity occur in the design conditions detailed in Table 2. The maximum elastic deflection in the unfavourable direction shall be determined for the load cases detailed in Table 2 using the characteristic loads. The resulting deflection is then multiplied by the combined partial safety factor for loads, materials and consequences of failure.
7.6.5.2 Blade (tip) deflection
One of the most important considerations is to verify that no mechanical interference between blade and tower will occur. In general, blade deflections have to be calculated for the ultimate load cases as well as for the fatigue load cases. The deflections caused by the ultimate load cases can be calculated based on beam models, FE models or the like. All relevant load cases from Table 2 have to be taken into account with the relevant partial load safety factors. Moreover, for load case 1 .1 extrapolation of tip deflection is mandatory according to 7.4.1 . Here direct dynamic deflection analysis can be used. The exceedance probability in the most unfavourable direction shall be the same for the characteristic deflection as for the characteristic load. The characteristic deflection is then to be multiplied by the combined safety factor for loads, materials and consequences of failure and be added to the un- deflected position in the most unfavourable direction and the resulting position compared to the requirement for non-interference.