Last Updated: 20222023.115
Wind
Basic Wind Speed (V): corresponds to a 3-sec gust speed at 33 ft (10 m) above the ground in Exposure Category C. Will be affected by patching for Metric vessels, the conversion from old to current will be to multiply the old value by 0.2778 and then round up to the nearest whole number. Units on form will be mph in Customary and m/s in Metric.
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Allow Wind Pressure to vary at different elevations: This checkbox is only an option for User Defined Wind for skirt supported vessels. If the checkbox is checked, the user may input multiple wind pressures at different elevations in the Attachments/Loadings screen under the Wind tab.
Add. Orthog. Load Fraction: Inputting a value here will add additional wind loading at 90 degrees (orthogonal) to the main load as a fraction. If you wish to have 30% orthogonal load, input 0.30. For vertical vessels (skirt supported, leg supported, lug supported or support ring supported), vector math will be used and the resultant vector load will be determined an used in the calculations. For horizontal vessels (saddle supported) this is handled in the calculation of Qc. This value defaults to zero.
Seismic
0.2 S Spectral Response Acceleration (Ss): mapped MCER , 5 percent damped, spectral response acceleration parameter at short periods.
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Force Distribution Factor: This input is only an option for User Defined Seismic for skirt supported vessels. It ranges from 1 to 2. The building codes determine this value based on the period of vibration of the vessel. This affects the vertical distribution of the horizontal seismic load. Higher k values push more of the load to the top of the vessel using the formula (W*H^k)/Sum(W*H^k) where W represents the weight of a segment of the vessel and H represents the elevation to the c.g. of that vessel segment.
Add. Orthog. Load Fraction: Inputting a value here will add additional seismic loading at 90 degrees (orthogonal) to the main load as a fraction. If you wish to have 30% orthogonal load, input 0.30. For vertical vessels (skirt supported, leg supported, lug supported or support ring supported), vector math will be used and the resultant vector load will be determined an used in the calculations. For horizontal vessels (saddle supported) this is handled in the calculation of Qc. This value defaults to zero.