Load Step Inputs
Load step inputs organize and manage the IDs of analysis parameter bulk cards.
Nastran Cards
Card  Description 

ACSRCE  Defines the power versus frequency curve for a simple acoustic source. 
DLOAD  Selects a dynamic load to be applied in a transient and
frequency response analysis subcase. The DLOAD command can also
be used to select a userdefined loading curve to be applied in a nonlinear static
analysis subcase. Note: Subcase Information Entry
Enable the subcase definition DLOAD and select load collectors with dynamic loading information (DLOAD, RLOAD1, RLOAD2, TLOAD1, TLOAD2). 
EIGC  Defines data needed to perform complex eigenvalue analysis 
EIGRA  Defines the data required to perform real eigenvalue
analysis with the Automated MultiLevel Substructuring technique. Note: Bulk Data Entry

EIGRL  Defines data required to perform real eigenvalue analysis
(vibration or buckling) with the Lanczos Method. Note: Bulk Data Entry

NLPARM  Activates nonlinear solution methods for this subcase
and to select the parameters used for Nonlinear Quasistatic Analysis, Geometric
Nonlinear Implicit Analysis, and Nonlinear Direct Transient Analysis. Note: Subcase Information Entry

RGYRO  Includes data required to perform Rotor Dynamics analysis
in Modal Frequency Response Analysis and/or Modal Complex Eigenvalue Analysis. The
RGYRO Bulk Data Entry is referenced by a corresponding
RGYRO Subcase Information Entry in a specific
subcase. Note: Bulk Data Entry

RLOAD1  Defines a frequencydependent dynamic load of the form: $\{P(f)\}=\left\{A\right\}[C(f)+iD(f)]{e}^{i\{02\pi f\tau \}}$ for use in frequency response problems 
RLOAD2  Defines a frequencydependent dynamic excitation of the form: $\{P(f)\}=\left\{A\right\}\cdot B(f){e}^{i\{\varphi (f)+02\pi f\tau \}}$ for use in frequency response problems 
TLOAD1  Defines a timedependent dynamic load or enforced motion of
the form:
$\{P(t)\}=\{A\cdot F(t\tau )\}$
for use in
transient response analysis 
TLOAD2  Defines a timedependent dynamic excitation or enforced
motion of the form:
$\{P(t)\}=\{\begin{array}{c}0\\ \left\{A\right\}{\tilde{t}}^{B}{e}^{C\tilde{t}}\mathrm{cos}(2\pi F\tilde{t}+P)\end{array}\begin{array}{c}\text{,}\\ \text{,}\end{array}\begin{array}{c}t(T1+\tau )\text{or}t(T2+\tau )\\ (T1+\tau )\le t\le (T2+\tau )\end{array}$
for use in a transient response
problem, where:
$\tilde{t}=tT1\tau $

OptiStruct Cards
Card  Description 

ACSRCE  Defines acoustic source as a function of power vs.
frequency. Note: Bulk Data Entry

BASELIN  Baseline correction 
DLOAD  Defines a dynamic loading condition for frequency response
problems as a linear combination of load sets defined via RLOAD1
and RLOAD2 entries, or for transient problems as a linear
combination of load sets defined via TLOAD1 and
TLOAD2 entries, or acoustic source ACSRCE
entries. Note: Bulk Data Entry

EIGC  Defines data required to perform complex eigenvalue
analysis. Note: Bulk Data Entry

EIGRA  Defines the data required to perform real eigenvalue analysis
with the Automated MultiLevel Substructuring technique. Note: Bulk Data Entry

EIGRL  Defines data required to perform real eigenvalue analysis
(vibration or buckling) with the Lanczos Method. Note: Bulk Data Entry

NLADAPT  The NLADAPT entry can be used in the Subcase
Information section to select the parameters used for Large Displacement Nonlinear
Quasistatic Analysis, Small Displacement Nonlinear QuasiStatic Analysis, and
Nonlinear Transient Analysis. Note: Subcase Information
Entry

NLENRG  Energy variable output 
NLMON  This NLMON Subcase Information Entry can be used to
activate Nonlinear Monitoring for a subcase by referencing a corresponding NLMON
Bulk Data Entry. Note: Subcase Information
Entry

NLOUT  The NLOUT entry can be used in the Subcase Information
section to select the incremental result output parameters used for Nonlinear Static
Analysis and Nonlinear Transient Analysis. Note: Subcase Information
Entry

NLPARM  Activates nonlinear solution methods for this subcase
and to select the parameters used for Nonlinear Quasistatic Analysis, Geometric
Nonlinear Implicit Analysis, and Nonlinear Direct Transient Analysis. Note: Subcase Information Entry

NLPRINT  Controls printing message. 
RGYRO  Includes data required to perform Rotor Dynamics analysis
in Modal Frequency Response Analysis and/or Modal Complex Eigenvalue Analysis. The
RGYRO Bulk Data Entry is referenced by a corresponding
RGYRO Subcase Information Entry in a specific
subcase. Note: Bulk Data Entry

RLOAD1  Defines a frequencydependent dynamic load of the form
$\mathbf{f}\left(\Omega \right)=A*B\left(\Omega \right){e}^{i\left(\varphi \left(\Omega \right)+\theta 2\pi \Omega \tau \right)}$
for use in frequency response problems.
RLOAD2 (Form 2) can be used when the frequencydependent
dynamic load input is available in magnitude/phase number format. Note: Bulk Data Entry

RLOAD2  Specifies directional combination method, modal combination
method, excitation direction(s), response spectra and scale factors. Note: Bulk Data Entry

TLOAD1  Defines a timedependent dynamic load or enforced motion.
Note: Bulk Data Entry

TLOAD2  Defines a timedependent dynamic excitation or enforced
motion. Note: Bulk Data Entry

UNBALNC  Defines the unbalanced rotating load during a rotor
dynamic analysis in Frequency Response solution sequences. The unbalanced load is
specified in a cylindrical system where the rotor rotation axis is the
Zaxis. Note: Bulk Data Entry
