Different Spring Elements (CELASi) in NASTRAN

[struclearner]

Dears,

NASTRAN has 4 different Spring Elements, CELAS1, CELAS2, CELAS3 and CELAS4. One difference between these elements is, how these are defined, by mentioning to PID or specifying K (Stiffness) values.
I could not find the mentioning of any other difference between these elements in NASTRAN User Guide. Are these elements, only differ in their formulations?
I will appreciate your input regarding the usage of these different Spring Elements and the difference between these.

Regards & Thanks

 

[dmapguru]

CELAS1 and CELAS2 need GRID points to define the springs. As you pointed out, CELAS1 uses a separate property entry to define the stiffness which may be preferable if many springs share the same coefficient and you are carrying out design optimization. CELAS2 defines the stiffness coefficient on the connection entry (no property entry is required). CELAS3 and CELAS4 need SPOINTs to define the springs, with the CELAS3 and CELAS4 following the same property logic as CELAS1 and CELAS2 respectively.
DG