We use the IMPACT line in Ship Impact analysis to define the ship impact load case. Details as below:

Load Case

The load case name is the name of the load case of the joint load applied at the node position where the ship collision occurs in the model file sacinp.

The applied node load reflects the direction of the ship collision; that is, it must be consistent with the direction of the ship collision.

The size of the applied node load and the coefficient of the corresponding load case in the command LDSEQ that defines the loading sequence in the clpinp file are used together for ship collision calculation. It must be ensured that the product of the load and the load coefficient can meet 100% energy absorption. Under the condition of meeting 100% energy absorption, there is no strict constraint on the size of the load.

Joint Name

When the ship collision position is only one node, enter the name of the node.

If you want to consider multiple point loading, leave it blank and set ‘Yes’ in ‘Use All Loaded Joints’. At the same time, apply node loads to all nodes considered for collision in the sacinp file and place them in the same load case setting.

Impact Energy Absorbed

If there is a constant energy value, enter it directly;

If not, leave it blank and set the energy parameters of the impact through the ENERGY command immediately following the IMPACT command. The program will calculate the energy value through API RP 2A C18.9.2.

Ship Indentation Curve Name

When it is necessary to consider the energy absorbed by the ship deformation during the ship collision, it is necessary to set the relationship curve between the selection force and the indentation value. Refer to DNV RP C204 3.5.2 Figure 3-4.

If the user customizes the relationship curve between the impact force and the indentation of the ship (using the SHPIND command), the corresponding custom curve name needs to be entered here.

Leaving this blank means that the absorption of energy by the ship deformation is not considered.

Exclude Automatic Unloading

Usually, unloading needs to be considered in ship collision analysis, that is, the process of the structure returning to its original position after the energy is completely absorbed. Refer to API RP 2A 18.9.2.

Denting Force Formula

When considering the energy absorbed by the dent of the member during the ship collision, it is necessary to set the relationship formula between the selection force and the dent value. Refer to API RP 2A C18.9.2.

At the same time, it is necessary to select a member in the Dent Calculation Member, and set the corresponding upper limit value, i.e. Member Dent Energy Limit- B Ratio (brace diameter/dent depth), Member Dent Energy Limit -%, and whether to consider the dent of the ship and member as plastic, i.e. the dent value cannot be restored.

A typical combination of ship collision analysis commands is shown in the figure below. Refer to the Collapse Advanced manual, section 5.6.2: