Last Updated: 20202023.5
NOTE: The above 6
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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Building Damping Coefficient: This is a field for skirt supports only.
Wind Pressure: This input is only an option for User Defined Wind. It allows the user to directly input the wind pressure. Be mindful of the units.
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 adds additional wind loading at 90 degrees (orthogonal) to the main load as a fraction. If you want to have 30% orthogonal load, input 0.30. For vertical vessels (skirt supported, leg supported, lug supported or support ring supported), vector calculations are then 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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Response Modification Factor (R): response modification coefficient as given by the specific Seismic Code.
TL: long-period transition period as defined by the Seismic Code, only affects skirt supported vessels.
Fa: short-period site coefficient (at 0.2 s-period) to be used if the value cannot be determined by . The greater of this value or that returned from tables in the referenced code will be used. Note that some cases for Site Class E and F do NOT have values in the codes, so it is critical that a value is input in these cases. This value is not used for ASCE 7-22 and later codes.
Fv: long-period site coefficient (at 1.0 s-period) to be used if the value cannot be determined by tables in the referenced codeThe greater of this value or that returned from tables in the referenced code will be used. Note that some cases for Site Class E and F do NOT have values in the codes, so it is critical a value is input in these cases. This value is not used for ASCE 7-22 and later codes.
SMS: the maximum short-period spectral response factor. This value is calculated for codes earlier than ASCE 7-22 and will not appear as an input. For ASCE 7-22 and later, this value is input by the designer.
SM1: the maximum 1 second spectral response factor. This value is calculated for codes earlier than ASCE 7-22 and will not appear as an input. For ASCE 7-22 and later, this value is input by the designer.
Skirt is sensitive to buckling: This checkbox only applies to Skirt supports. And if checked it will adjust the CR-I value to a greater value in some cases resulting in a higher load value.
ap: the amplification factor related to the response of a system or component as affected by the type of seismic attachment; this is only used for vessels designs as supported by another structure. This value is not used for ASCE 7-22 and later codes.
CAR: the component resonance ductility factor; this is only used for vessel designs supported by another structure. This value is used for ASCE 7-22 and later codes.
Rmu: the structural ductility reduction factor; this is only used for vessel designs supported by another structure. This value is used for ASCE 7-22 and later codes.
Use ASCE 15.4.1 Step 2 exception: Checking this box will invoke the exception as described in ASCE and will adjust the Cs calculation and typically results in a lower load value.
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Tv: This is a user input for the ASCE 7-16 and later code yearyears. The default is set to 0.1 to give conservative estimations within the software. The user can input values but only the range from 0 to 2 is usable within the equations. Values outside of this range will be taken equal to the upper or lower bound.
Top Force Multiplier: This input is only an option for User Defined Seismic for skirt supported vessels . This should be entered as a decimal (e.g. 10% would be entered as 0.1). This value will be used to set a portion of the vessel horizontal seismic load at the top of the vessel (Weight * Top Force Multiplier * FPV * Ceh), the remaining horizontal seismic load will then be vertically distributed over the vessel based on the weight distribution and the k factor.
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.