Non-structural Mass

Non-structural mass may be specified in two different ways.

Many property definitions (PSHELL, PCOMP, PBAR, PBARL, PBEAM, PBEAML, PROD, CONROD, PSHEAR, and PTUBE), have an NSM data field that allows a value of non-structural mass per unit area or non-structural mass per unit length to be defined.
When non-structural mass is defined in this way, it is considered in all analyses.
Non-structural mass may be defined via a number of non-structural mass Bulk Data Entries (NSM, NSM1, NSML, NSML1, and NSMADD) for a list of elements or properties. In the case of a list of properties, non-structural mass is applied to the elements referencing the properties in the list.
These non-structural mass definitions must be selected for use in an analysis through the NSM Subcase Information Entry.
The NSM Subcase Entry is currently subcase-dependent only for Linear Static and Nonlinear Static Analysis. For all other solution sequences, the NSM Subcase Entry should be defined globally above the first SUBCASE statement. If the NSM Subcase Entry is specified within any subcase which is not linear static or nonlinear static, then the run will be terminated with an error.
- Input non-structural mass per unit area/length/volume (NSM/NSM1)
  The NSM Bulk Data Entry and its alternate form NSM1 allow you to define a value of non-structural mass per unit area, non-structural mass per unit length, or non-structural mass per unit volume to be applied to a selected list of elements
  
  The NSM field on various property entries listed above also inputs mass per unit area/length/volume directly.
- Input lumped non-structural mass (NSML/NSML1)
  The NSML Bulk Data Entry and its alternate form NSML1 allow you to allocate and smear a lumped non-structural mass value to be evenly distributed over a list of elements.
  - Default Distribution (DTYPE=blank on NSML/NSML1)
    The non-structural mass value per unit area, per unit length, or per unit volume to be applied to the elements is: (1)
    $N S M_{per unit area} = \frac{V A L U E}{\sum_{i = 1}^{n} A_{i}}$
    (2)
    $N S M_{per unit length} = \frac{V A L U E}{\sum_{i = 1}^{n} L_{i}}$
    (3)
    $N S M_{per unit volume} = \frac{V A L U E}{\sum_{i = 1}^{n} V_{i}}$
    
    For the default case when DTYPE is blank, referencing a mixture of different element or property types is not supported.
  - Distribution based on Mass/Volume (DTYPE=MASS/VOLUME on NSML/NSML1)
    The non-structural mass value per unit mass or volume to be applied to the elements is: (4)
    $N S M_{per unit mass} = \frac{V A L U E}{\sum_{i = 1}^{n} M_{i}}$
    (5)
    $N S M_{per unit volume} = \frac{V A L U E}{\sum_{i = 1}^{n} V_{i}}$
Where,

$n$

Number of elements in the set

$V A L U E$

Value of the lumped mass

$L_{i}$

Length of element $i$

$A_{i}$

Area of element $i$

$V_{i}$

Volume of element $i$

$M_{i}$

Mass of element $i$

An important difference between the default distribution (DTYPE=blank) and DTYPE=MASS/VOLUME, is that a mixture of multiple element types (1D, 2D, and 3D elements) can be defined on a single NSML/NSML1 entry when TYPE field is set to ELEMENT/ELSET (mixture of elements) or MIXED (mixture of properties).

The NSMADD Bulk Data Entry allows you to form combinations of NSM, NSM1, NSML, and NSML1.

An element can have more than one non-structural mass value specified for it. The actual non-structural mass value will be the sum of all of the individual non-structural mass values.