Diff between MPC and SPC 1

[c89666]

What actually MPC and SPC sounds.MPC-multi pt constrant and SPC- single point constrant.
SPC are used for fixing a component or model but MPC are use to define the relation of set of nodes with one.
what i understood is correct? or is there any additional difference between them thnxs

 

[zuardy]

Hi,
you are right, but actually both (SPC & SPC) can be used to constrain (not only fixing) a model. The difference is only that SPC is implemented for each node, so there is no relation between the nodes (DOFs). MPC in other hand constrains the model by connecting some nodes (independent DOFs) to a node (dependent DOF).
It seems like nodal Load and surface (element) load. in surface load there is a relation (function) between the nodal loads.
Hope this makes it clear.

regards

 

[idly123]

MPC and SPC are virtually the same. One can not argue in terms of relationships between nodes or DOFs. Having specified SPC at a point it would definetly affect all other DOFs. MPC can be used as a load transfer mechanism and idelaisation , especially when u have members connecting with different DOFs or if u have a inclined support, sinking support its effective
raj

 

[zuardy]

Hi,
thanks for the comment raj, you are right that "Having specified SPC at a point it would definetly affect all other DOFs". One can easy imagine that if a DOF is fixed, then the adjacent DOF could not have a huge diplacement, this must be discontinous!
But take care about the therms "relation" and "affect". With relation i mean that the "effect" of one DOF to another is predefined or in preprocessing stage. But if only SPC is implemented to a DOF then the "effect" is obtained after the solution, this is clear because the DOFs is related to another via stiffness matrix in the equation : Ku = f.
Hope this make the misunderstanding clearly

regards