Good day Sirs.
I have s situation where Analysis is required for a Pipeline to be used as an underwater vent. How would I set up the Load cases (how would the forces as a result of the release of Gases into the sea be represented)? Also, the Pipeline is resting on the Seafloor. I have the intention of considering the soil reactions as springs; my question is, how would the spring constant be "uniformly distributed" across the span of the Pipeline. Code is B31.8

Load case for vent line in this situation should be same as normally used. I suppose you will go for static analysis only, by calculating vent thrust load and applying it in relief valve elbow. For calculating back thrust water density should be used.

For uniform distribution of spring stiffness of sea bed, I am not aware of any special method CAESAR provides. Current practice is to calculate stiffness for whole element and divide it into two parts and applying at each node. So for each node you have two elements joining on it hence half reaction from each element will be added to each node. Only boundary nodes will have half element reaction. By taking small length of each element you can be closure to “uniform distribution”.