TR.32.11 Repeat Load Specification
This command is used to create a copy of the load items defined in primary and reference load cases that have been previously defined in the file with the values of the loading in those case, scaled with a suitable factor.
General Format
REPEAT LOAD
i1, f1, i2, f2 … in, fn
Where:
| Parameter | Description |
|---|---|
| i1, i2 … in | primary load case numbers |
| f1, f2 … fn | corresponding factors |
This command can be continued to additional lines by ending all but last with a hyphen. Limit of 550 prior cases may be factored.
Selected primary load cases may themselves include REPEAT LOAD commands which are accounted for by a combined factor from both REPEAT LOAD commands.
Description
This command may be used to create a primary load case using combinations of previously defined primary load case(s). The REPEAT LOAD differs from the load COMBINATION command (See TR.35 Load Combination Specification) in two ways:
- A REPEAT LOAD is treated as a new primary load. Therefore, a
P-Delta analysis will reflect correct secondary effects.
(LOAD COMBINATIONS, on the other hand, algebraically combine the results such as displacements, member forces, reactions and stresses of previously defined primary loadings evaluated independently).
- In addition to previously defined primary loads, you can also add new loading conditions within a load case in which the REPEAT LOAD is used.
-
The REPEAT LOAD option is available to factor prior load case data and add those forces into the current load case.
The load case data types that will be factored include Joint Loads, Member loads, Element loads, Inertia Loads, Fixed End loads, Selfweight loads, Displacements, Area loads, Prestress loading, and Temperature loads. Floor loads, Wind loads Snow loads, and UBC loads are first converted to equivalent member loads and then factored.
Modal dynamic analysis load cases (Response Spectrum, Time History, Steady State) should not be used in REPEAT LOAD. It is also not available for loads generated using some of the program’s load generation facilities such as MOVING LOAD Generation. However load cases with WIND LOAD may be used in Repeat Load.
UBC cases may only be used in REPEAT LOAD if there is a PERFORM ANALYSIS and CHANGE command after each UBC case. See notes with UBC LOAD command.
Prestress on a given member from 2 or more load cases cannot be combined.
Example 1: Using Repeat Loads
LOAD 1 DL + LL SELFWEIGHT Y -1.4 MEMBER LOAD 1 TO 7 UNIFORM Y -3.5 LOAD 2 DL + LL + WL REPEAT LOAD 1 1.10
Example 2: Re-use of Repeat Loads
For a load case that is defined using the REPEAT LOAD attribute, the constituent load cases themselves can also be REPEAT LOAD cases. For load cases 4 in this example, the selfweight values from load case 1 will be multipled by a combined factor of 1.5 × 1.25 = 1.875.
LOAD 1 SELFWEIGHT Y -1.0 LOAD 2 MEMBER LOAD 2 UNI GY -1.5 LOAD 3 REPEAT LOAD 1 1.5 LOAD 4 REPEAT LOAD # Includes repeat load from Load Case 3 2 1.2 3 1.25