11. How AutoPIPE is calculating the added mass during the static seismic analysis in subsea pipeline


Applies To
Product(s):AutoPIPE
Version(s):ALL;
Area: Static Seismic Analysis
Date Logged
& Current Version		May 2022
12.08.00.063

Problem:

How AutoPIPE is calculating the added mass during the static seismic analysis in subsea pipelines or piping or if we are required to add the hydrodynamic added mass based on selected coefficients Ca values? 

Solution:

AutoPIPE adds an additional weight component to the unit pipe weight for Static Seismic Analysis when the Additional Mass Coefficient Value (Ca) is greater than zero. As shown in screenshot below:

The additional unit weight is calculated based on the following equation:

Where:

Wadd       =              Additional unit weight of pipe for Static Seismic analysis for submerged piping

Do           =              Outside diameter of pipe including Insulation and Refractory thickness

fs             =              Factor for submerged pipes: 0.0 when pipe not submerged or Segment flag for buoyancy turned off, 0.5 when one end of pipe is submerged, 1.0 when both ends of pipe are submerged

G             =              Specific gravity of Water (defined in Buoyancy dialog)

Ca            =              Added mass coefficient Ca (defined in Buoyancy dialog)

The rest of the static seismic calculations are carried out as usual after adding this additional unit weight to the weight of the pipe.
With this information, we can say that AutoPIPE uses Ca for Static Seismic and Modal analysis (affecting Response Spectrum and Time History analysis). It would be for them to decide which analysis to choose for their submerged piping.

See Also

Bentley AutoPIPE