This document describes how to introduce tension relief devices shock absorbers / mooring dampers into analysis model of mooring lines.

Wanting to introduce a tension relief device (TRD) into the mooring line I click on the element which is where covering the area where I want to introduce it. Then click on the split element button and choose “Split at distance” as shown in Figure 1. The length chosen at “Split at distance” should correspond to the length of the tension relief device to be introduced.

Then click on the element towards the node where you would like to introduce the spring. Then an element with desired length is established as seen in Figure 1.

The new elements are moved to the component that will represent the TRD.

The TRD is modeled as a truss element just like the moorings are. Figure 3 shows this component which have a table describing the relationship between elongation and axial force in the TRD.

Components having nonlinear relation between force and elongation also need to have the linear parameters set. In this demo, the spring is assumed to be a cylinder with diameter 113 mm and a weight of 20 kg = 20 kg / m for this case as shown in Figure 4.

TRDs may or may not have damping. Damping can be introduced by going into det “Damper” section and introducing relevant data as shown in Figure 5

Having a component describing the TRD, one can introduce as many as one would like as seen in Figure 5 where there is a total of 3 TRDs.