Subcases are defined in the subcase information section of the input file. Subcases are used to combine loads and boundary conditions (detailed in the bulk data section of the input file) so that a number of different analyses can be performed on the same geometric and material data in one solver run. A description of all valid subcase information entries can be accessed from the List of Subcase Information Entries (by function) page of the Reference Guide section.
Individual subcases are defined using the SUBCASE statement (if only one subcase is to be solved, the SUBCASE statement is not necessary). Each subcase must have a unique Integer ID. The loads and boundary conditions pertaining to each subcase are referenced in the lines immediately following the SUBCASE statement. Information pertaining to a subcase ends with a new SUBCASE statement or the BEGIN BULK statement. Certain subcase information entries preceding the first SUBCASE statement apply to all subcases unless the same entry appears within a subcase; in which case, the entry preceding the first subcase is ignored for that subcase.
As already stated, the solution sequence for each subcase is automatically determined based on the contents of that subcase. This is outlined in more detail below:
A linear static analysis is carried out when a subcase contains static loads and single point constraints.
At least one single-point constraint reference is required for a linear static analysis. If you want to run an analysis without single-point constraints, SPC = 0 may be used.
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SUBCASE 5 |
$ Defines subcase number 5 |
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LOAD = 6 |
$ references all static load cards with SID = 6 |
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SPC = 7 |
$ references all single-point constraints with SID = 7 |
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MPC = 10 |
$ references all multi-point constraints with SID = 10 |
A nonlinear quasi-static gap analysis is carried out when a nonlinear parameter card (NLPARM) is present in a linear static subcase.
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SUBCASE 7 |
$ Defines subcase number 7 |
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LOAD = 6 |
$ references all static load cards with SID = 6 |
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SPC = 7 |
$ references all single-point constraints with SID = 7 |
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NLPARM = 9 |
$ references NLPARM (bulk data entry) with ID = 9 |
A linear buckling analysis is carried out when the subcase references a linear static subcase through a STATSUB card and a real eigenvalue extraction card through a METHOD card.
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SUBCASE 3 |
$ Defines subcase number 3 |
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STATSUB = 5 |
$ references linear static subcase number 5 |
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METHOD = 3 |
$ references EIGRL card with SID = 3 |
A normal modes analysis is carried out when the subcase references a real eigenvalue extraction card.
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SUBCASE 4 |
$ Defines subcase number 4 |
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METHOD = 4 |
$ references EIGRL card with SID = 4 |
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SPC = 7 |
$ references all single-point constraints with SID = 7 |
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MPC = 10 |
$ references all multi-point constraints with SID = 10 |
A direct frequency response analysis is carried out when the subcase references a frequency response dynamic load.
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SUBCASE 2 |
$ Defines subcase number 2 |
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DLOAD = 1 |
$ references RLOAD# or DLOAD (bulk data entry) with SID = 1 |
Modal frequency response analysis is carried out when the subcase references a real eigenvalue extraction card in addition to a frequency response dynamic load.
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SUBCASE 1 |
$ Defines subcase number 1 |
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DLOAD = 1 |
$ references RLOAD# or DLOAD (bulk data entry) with SID = 1 |
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METHOD = 2 |
$ references EIGRL card with SID = 2 |
Random response analysis is carried out when the RANDOM subcase information entry is present anywhere in the subcase information section of the input.
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RANDOM = 11 |
$ references RANDPS and RANDT1 with SID = 11 |
A direct transient response analysis is carried out when a subcase references a transient dynamic load and TSTEP(TIME) is used to reference time step information.
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SUBCASE 2 |
$ Defines subcase number 2 |
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DLOAD = 1 |
$ references TLOAD# or DLOAD (bulk data entry) with SID = 1 |
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TSTEP(TIME) = 12 |
$ references TSTEP (bulk data entry) with SID = 12 |
A modal transient response analysis is carried out when a subcase references a transient dynamic load and a real eigenvalue extraction card and TSTEP(TIME) is used to reference time step information.
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SUBCASE 2 |
$ Defines subcase number 2 |
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DLOAD = 1 |
$ references TLOAD# or DLOAD (bulk data entry) with SID = 1 |
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TSTEP(TIME) = 12 |
$ references TSTEP (bulk data entry) with SID = 12 |
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METHOD = 2 |
$ references EIGRL card with SID = 2 |
A direct transient response analysis is carried out when a subcase references a transient dynamic load and TSTEP(FOURIER) is used to reference time step information.
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SUBCASE 2 |
$ Defines subcase number 2 |
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DLOAD = 1 |
$ references TLOAD# or DLOAD (bulk data entry) with SID = 1 |
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TSTEP(FOURIER) = 12 |
$ references TSTEP (bulk data entry) with SID = 12 |
A modal transient response analysis is carried out when a subcase references a transient dynamic load and a real eigenvalue extraction card and TSTEP(FOURIER) is used to reference time step information.
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SUBCASE 2 |
$ Defines subcase number 2 |
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DLOAD = 1 |
$ references TLOAD# or DLOAD (bulk data entry) with SID = 1 |
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TSTEP(FOURIER) = 12 |
$ references TSTEP (bulk data entry) with SID = 12 |
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METHOD = 2 |
$ references EIGRL card with SID = 2 |
An inertia relief analysis is carried out when fictitious supports (SUPORT1) cards are referenced from within a linear static, nonlinear gap, modal frequency response (with residual vectors), or transient response (with residual vectors) subcase, when SUPORT entries are defined in the bulk data section or when PARAM,INREL,-2 is defined in the bulk data section.
If PARAM,INREL,0 is included in the bulk data section, the fictitious supports (SUPORT and SUPORT1) behave as single-point constraints.
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SUBCASE 6 |
$ Defines subcase number 6 |
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LOAD = 6 |
$ references all static load cards with SID = 6 |
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SUPORT1 = 8 |
$ references all SUPORT1 cards with SID = 8 |