Load Combinations
Overview
REPTILE's load combinations work by writing data to a CSV file like normal and then combining the CSV results as defined by the combination definition file (.comb). This can be done either automatically by supplying a .comb file instead of XDB files, or manually after the fact by invoking the --combine mode from the command line.
Combination Definition File
The input file for that REPTILE uses for load combinations is a text file that consists of three distinct parts, which are described in more detail below:
Notes on Formatting:
1. DEFINING SOURCE FILES
This section of the file defines the XDB source files to be used in the combinations, and assigns them IDs. Source Definition input lines take the form: "SRC, ID, FILENAME" where:
Example:
- Defining the source files
- Creating aliases (optional)
- Defining the load combinations
Notes on Formatting:
- Comment lines are indicated with a "#" symbol
- Blank lines are ignored
- All input lines are comma delimited (so no commas within fields)
- Leading and trailing spaces are ignored (can be used for readability)
- All SRC's and ALIAS's must be defined before the COMB's
1. DEFINING SOURCE FILES
This section of the file defines the XDB source files to be used in the combinations, and assigns them IDs. Source Definition input lines take the form: "SRC, ID, FILENAME" where:
- SRC is a keyword indicating that we are defining a source
- ID is a string that will be used to refer to the source
- FILENAME is the name of the XDB file containing the loads
Example:
SRC, AIR, air_loads.xdb
SRC, WNG, wing_bending.xdb
SRC, NOM, nominal.xdb
SRC, MAX, max.xdb
2. CREATING ALIASES (OPTIONAL)
Aliases are completely optional, but may be used to make the combination definitions more readable, since refering to a character string may be more clear to a human than refering to a numerical subcase ID.
Alias Definition input lines take the form: "ALIAS, ID, SRC.SC" where:
ALIAS IDs cannot contain periods (to distinguish them from SRC.SC)
Example:
Aliases are completely optional, but may be used to make the combination definitions more readable, since refering to a character string may be more clear to a human than refering to a numerical subcase ID.
Alias Definition input lines take the form: "ALIAS, ID, SRC.SC" where:
- ALIAS is a keyword indicating that we are defining an alias
- ID is a string that will be used to refer to the subcase
- SRC.SC is refers to a source file and the subcase within that file
ALIAS IDs cannot contain periods (to distinguish them from SRC.SC)
Example:
ALIAS, BLAH, AIR.1
ALIAS, FOO, AIR.34
3. DEFINING THE LOAD COMBINATIONS
This section defines the Load Combinations.
Load Combination input lines take the form: "COMB, ID, DESCRIPTION, ALL_FACTOR, FACTOR, SRC.SC, FACTOR, ALIAS ... [etc]" where:
Example:
This section defines the Load Combinations.
Load Combination input lines take the form: "COMB, ID, DESCRIPTION, ALL_FACTOR, FACTOR, SRC.SC, FACTOR, ALIAS ... [etc]" where:
- COMB is a keyword indicating that we are defining a load combination
- ID is a compact load case identifier
- DESCRIPTION is a string description of the combined load case
- ALL_FACTOR is a scale factor applied to the sum of individual components
- FACTOR is a scale factor applied to the following subcase
- SRC.SC refers to a source file and the subcase within that file
- ALIAS may optinally be used in place of SRC.SC to refer to a subcase
Example:
COMB, 101, ULT 15312 + C4, 1.50, 1.0, BLAH, 1.0, WNG.3
COMB, 201, DSD 24783 + C3 + Nom, 1.25, 1.0, AIR.34, 1.0, WNG.17, 1.25, NOM.1
COMB, 202, DSD 24783 + C3 + Max, 1.25, 1.0, FOO, 1.0, WNG.17, 1.0, MAX.1
COMB, 302, FAIL 15312 + C4, 1.25, 1.0, AIR.1, 1.0, WNG.2
Command Line
There are two ways to generate load combinations with REPTILE:
- Manually, using --combine mode, which operates on an existing CSV file:
reptile --combine -i file.comb -o output.csv file1.csv
- Automatically, by using the -COMB option for another REPTILE function instead of specifying XDB files:
reptile --node_forces -i file.def -o output.csv -COMB file.comb