TR.31.6 Defining Reference Load Types
This converts a real load case to something similar to a load case definition. A reference load case is solved only when it is later called in a load case. The benefit is that it enables you to define as many load cases as you wish, but instruct the program to actually solve only a limited number of "real" load cases, thus limiting the amount of results to be examined.
See TR.33 Reference Load Cases - Application for a description of the procedure for specifying the reference load information in active load cases.
General Format
DEFINE REFERENCE LOADS
LOAD R(i) LOADTYPE (type) TITLE load_title
(Load items)
…
END DEFINE REFERENCE LOADS
Example
DEFINE REFERENCE LOADS LOAD R1 LOADTYPE Dead TITLE REF DEAD SELFWEIGHT Y -1 JOINT LOAD 4071 4083 4245 4257 FY -4.04 4090 FY -0.64 ELEMENT LOAD 378 TO 379 406 TO 410 422 TO 426 PR GY -1.44 MEMBER LOAD 5006 TO 5229 UNI GY -0.64 PMEMBER LOAD 1 TRAP GY -0.347 -0.254 35.5 42 LOAD R2 LOADTYPE Live TITLE REF LIVE JOINT LOAD 4209 FY -6.63 4071 4083 4245 4257 FY -1.71 LOAD R3 LOADTYPE Snow TITLE REF SNOW JOINT LOAD 4109 FY -8.69 4071 4083 4245 4257 FY -3.29 LOAD R4 LOADTYPE Soil TITLE REF SOIL ELEMENT LOAD 1367 TO 1394 1396 1398 1522 1539 TO 1574 - 1575 TRAP JT -0.78 -0.78 -0.719167 -0.719167 LOAD R4 LOADTYPE mass TITLE Mass Model SELFWEIGHT X 1 SELFWEIGHT Y 1 SELFWEIGHT Z 1 JOINT LOAD 17 TO 48 FY -2.5 49 TO 64 FY -1.25 END DEFINE REFERENCE LOADS
Mass Modeling Using Reference Loads
A reference load case of type MASS can be created which can then be used to define the structure mass used for all dynamic analyses (i.e., seismic, response spectrum, time history, etc.). Some analysis methods require you to create separate weight tables in the form of SELFWEIGHT, MEMBER WEIGHT, JOINT WEIGHT, etc. for each analysis, thus resulting in repetition of the same information. Using a LOADTYPE MASS reduces the repetitive data entry and the need for manually creating a weight table.
A mass model using this method is defined once and then used for all dynamic analyses.
If the LOADTYPE MASS is missing and no mass is defined in the corresponding seismic or dynamic analysis load cases, the program will report error as mass is missing. If a mass table is provided in a seismic load definition, response spectrum definition, or time history loading definition, then that mass table will be used for analysis under those loads only instead of a mass model generated by a REF LOAD TYPE MASS. However, if no masses are defined within the individual seismic, response spectrum, or time history load definitions, then the program uses the mass reference load case when analyzing that seismic or dynamic load case.