TIA SWT Support Structure Design Supplement Draft 03292011 R0

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ANSI/TIA-222-G-DS1-2011 DRAFT 3-29-2011 Rev 0 8.0 CRITICAL TURBINE MOMENTS Unless otherwise specified by the turbine manufacturer, the extreme wind condition shall be assumed to govern over other turbine operational loading conditions that subject the supporting structure to an overturning or twisting moment. These conditions include braking, shorts, shut down, maximum rotational speed condition, extreme yawing, etc. When a critical turbine moment is specified by the turbine manufacturer, the moment shall be investigated by considering an additional extreme wind loading condition without ice. Unless otherwise specified, the specified moment shall be considered to occur simultaneously with a 25 mph [11 m/s] basic wind speed with the calculated effective projected area of the turbine (EPA) T and the TIA importance factor, I, for wind load without ice, based on the structure classification. Unless otherwise specified, a load factor of 1.6 shall be applied to the specified moment. A specified overturning moment shall be considered to occur at the top of the structure in the same direction as the wind. A specified twisting (yaw) moment shall be considered to act about the vertical centerline of the turbine base in a counterclockwise direction in the plan view. 9.0 SERVICEABILITY REQUIREMENT Unless otherwise specified, the stiffness of the supporting structure shall result in a tip deflection no greater than 1% of the structure height for the TIA service loading condition (60 mph [27 m/s] basic wind speed without ice) with the calculated effective projected area of the turbine (EPA) T . 10.0 DYNAMIC REQUIREMENTS The natural frequency modes involving single, double and triple curvature of the supporting structure shall be determined for a no-ice condition when natural frequencies of the support structure to be avoided are specified by the turbine manufacturer. One of the elastic three-dimensional models specified in TIA shall be used to determine the fundamental frequency modes. The simplified TIA fundamental frequency equations shall not be used for SWT supporting structures. The masses of the turbine, the structure and all appurtenances shall be included in the structural model at the proper locations. Unless a detailed analysis is undertaken to determine an appropriate foundation spring constant to be used in the determination of natural frequencies, the calculated natural frequencies of the structure shall be adjusted +/- 10% for comparison to the turbine manufacturer’s specified natural frequencies. When frequency ranges or min/max frequencies are provided by the turbine manufacturer, no adjustments to the calculated natural frequencies of the supporting structure are required. Note: Natural frequency modes involving torsion may require investigation for vertical axis turbines when specified by the turbine manufacturer. 6
ANSI/TIA-222-G-DS1-2011 DRAFT 3-29-2011 Rev 0 11.0 FATIGUE STRENGTH 11.1 Equivalent Constant Range Wind Loading on Supporting Structure Unless otherwise specified, fatigue wind loading on the supporting structure and supported appurtenances (excluding the turbine) shall be considered as an additional service loading combination (K fd = 0.85 for all structures) using a 30 mph [13 m/s] uniform wind speed (K z , K zt and G h equal to 1.0) and the importance factor for fatigue loading specified in Table 11-1 based on the TIA structure classification for the supporting structure. The fatigue loading on the supporting structure shall be considered to occur simultaneously with the equivalent constant range turbine loads specified in Section 11.2. 11.2 Equivalent Constant Range Turbine Loads Equivalent constant range fatigue loads for horizontal axis turbines shall be calculated from the following equations: Fxt = equivalent constant range turbine horizontal force, lbs [N] = (K fd )(I f )(C fxt )(Dr) 2 Mty = equivalent constant range turbine overturning moment, ft-lbs [N-m] = (K fd )[2(Wtr)(Lrc) + (Dr)(Fxt) / 12] Mtx = equivalent constant range turbine shaft torsion, ft-lbs, [N-m] = (K fd )[(I f )(C mtx )(Dr) 2 / Nr + 0.005(Wtr)(Dr)] where: K fd = 0.85 I f = importance factor for fatigue from Table 11-1 C fxt = 1.0 [48] Dr = rotor diameter, ft [m] Wtr Lrc = weight of rotor (hub and blades), lbs [N] = distance between center of gravity of rotor and centerline of the supporting structure, ft [m] C mtx = 275 [4000] Nr = rotor rotational speed, rpm Note: K fd accounts for the probability of the applied load range occurring form a direction that creates a response in any one given support structure component. The horizontal force, Fxt, shall be applied concentrically in the direction of the wind at the hub height of the turbine. The overturning moment, Mty, shall be applied at the top of the supporting structure in a vertical plane in the direction which adds to the overturning moment resulting from Fxt. The moment, Mtx, shall be applied at the top of the supporting structure in a vertical plane normal to the wind direction (shaft torsion). 7
Page 1 and 2: ANSI/TIA-222-G-DS1-2011 DRAFT 3-29-
Page 5 and 6: SMALL WIND TURBINE SUPPORT STRUCTUR
Page 7 and 8: 1.2 Turbine Model ANSI/TIA-222-G-DS
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Page 17 and 18: 14.0 MAINTENANCE AND CONDITION ASSE
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TIA SWT Support Structure Design Supplement Draft 03292011 R0

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