Hello,
I wonder how to obtain the mass and stiffness matrices of the problem I am working with. The structural problem is modelled using 3D shell elements, with a total of 624 nodes of which 12 nodes are constrained, i.e. with 612*6=3672 degrees of freedom. My intention is to obtain the mass and stiffness matrices of the constrained structure, i.e. the matrices with size (3672x3672) and the description of the degrees of freedom. The livelink for matlab function mphmatrix gives me either:
Unconstrained mass and stiffness matrices E and K with size (14832x14832)
Constrained mass and stiffness matrices Ec and Kc with size (12240x12240)
I don't understand why the constrained matrices have more degrees of freedom than: number of degrees of freedom per node x number of nodes
Kind regards,
Lucas