TR.50 Group Specification
This command may be used to group members together for analysis and steel design.
General Format
(FIXED GROUP)
GROUP (prop-spec) MEMBER memb-list (SAME AS i1)
prop-spec = { AX | SY | SZ }
Where:
| Parameter | Description |
|---|---|
| SAME AS i1 | member number used in the SAME AS command. If provided, the program will group the members based on the properties of i1. |
Description
This command enables the program to group specified members together for analysis based on their largest property specification.
When FIXED GROUP is omitted, the GROUP command is usually entered after the member selection command, and the selected members will be grouped immediately and the new member properties will be used in any further operations. After the grouping is completed, the GROUP commands are discarded and will not be used again. Further grouping will be done only if a new GROUP command is encountered later.
If the FIXED GROUP option precedes the group data, the specified grouping will be retained in memory by the program and will be used in subsequent SELECT commands. No grouping will occur unless a SELECT (MEMBER or ALL or OPTIMIZED) command is performed. However, grouping will be performed with every subsequent SELECT command.
Example 1
SELECT ALL GROUP SZ MEMB 1 3 7 TO 12 15 GROUP MEMB 17 TO 23 27 SAME AS 30
In this example, the members 1, 3, 7 to 12, and 15 are assigned the same properties based on which of these members has the largest section modulus. Members 17 to 23 and 27 are assigned the same properties as member 30, regardless of whether member 30 has a smaller or larger cross-sectional area. AX is the default property upon which grouping is based.
Example 2
FIXED GROUP GROUP MEMB 1 TO 5 SELECT OPTIMIZED
In the above example, the usage of the FIXED GROUP command is illustrated. In this example, the SELECT OPTIMIZED command involves the six stage process of
-
CHECK CODE ALL followed by modification of RATIO
-
SELECT ALL
-
GROUPING MEMBERS 1 TO 5
-
PERFORM ANALYSIS
-
SELECT ALL
-
GROUPING MEMBERS 1 TO 5
The FIXED GROUP command (and the GROUP commands that follow it) is required for execution of steps 3 and 6 in the cycle. You may want to repeat this data for further optimization.
Notes
The FIXED GROUP + GROUP commands are typically entered before the member selection for further analysis and design. This facility may be effectively utilized to develop a practically oriented design where several members need to be of the same size.
All the members in a list for a specific GROUP command should have the same cross section type. Thus, if the command reads
GROUP MEMB 1 TO 10
and member 3 is a W shape and member 7 is a Channel, grouping will not be done. The 10 members must be either all W shapes or all channels.
Also, refer to Note 'C' in TR.49.1 Member Selection Specification.