Masses
Self-weight masses can be defined by using the UDL load type "Self-weight" (G or GM). Additional mass definitions are defined with the herein described load types. All masses defined with these types are specified as forces (weights), but only used in dynamic calculations as accelerated masses. They must separately be defined with the appropriate static load types, if they should also be considered as loads in static analyses.
Nodal masses – load types NDMAS, NDSMASE, NDMASI, NDMASA
| Load Type | Description |
|---|---|
| NDMAS | Concentric nodal masses specified as diagonal tensor, containing the mass terms in the global coordinate directions (g×mx, g×my, g×mz) and the mass moments of inertia (g×Imx, g×Imy, g×Imz) around the global axis directions. Note that all three mass terms must essentially be specified, although they usually have the same value because mass is a scalar property. |
| NDMASE | Eccentric nodal masses specified by the mass components g×mx, g×my, g×mz and the eccentricity vector ex, ey, ez (from the node to the gravity centre of the point mass). Any mass moments of inertia around the gravity centre of the point mass are neglected, or must be superimposed by additionally using the load type NDMASI or NDMASA. |
| NDMASI | Definition of the full tensor (g×Imx, g×Imy, g×Imz, g×Imxy, g×Imxz, g×Imyz) of mass moments of inertia with respect to the global coordinate system. |
| NDMASA | Nodal mass moments of inertia (g×Imx, g×Imy, g×Imz) around a local axis system defined by specifying angles Beta, Alpha1, Alpha2 and calculated like the local coordinate system of beam elements (type Deck). |
>Element masses – load types ELMAS, ELSMASE
| Load Type | Description |
|---|---|
| ELMAS | Uniformly distributed element masses specified as vector containing the mass terms per unit length for the local coordinate directions (g×mx, g×my, g×mz) and the mass moments of inertia per unit length (g×Imx, g×Imy, g×Imz) around the local axis directions. Note that all three mass terms must essentially be specified, although they usually have the same value due to mass being a scalar property. Any mass moment of inertia terms around the local y and z-axes are currently neglected, although their specification is accepted. |
| ELMASE | Eccentrically acting uniformly distributed masses, specified by the mass components g×mx, g×my, g×mz; the mass moment of inertia around the local x direction, and the eccentricity components ey, ez (local direction, from the start and end nodes to the gravity centre of the line mass). |
Note that all element masses are uniformly distributed over the whole clear element length. Any specified eccentricities are related to the node points, i.e. the cross-section eccentricity is automatically considered. For creating the mass matrices, the distributed masses (and inertia terms around x-local) are lumped to the start and end nodes without generating rotational inertia terms around the local y- and z-axes. Therefore, in order to get accurate results, a suitable subdivision into small elements has to be made for beams subject to dynamic impacts. The lumped torsional mass moment of inertia is added to any terms g×my×ez2 and g×mz×ey2 due to eccentric mass application. After transforming this value into global directions, it is directly applied as nodal mass moment of inertia without further eccentricity transformation.