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TR.25.1 Member Offset Specification

This command may be used to rigidly offset a frame member end from a joint to model the offset conditions existing at the ends of frame members.

General Format

MEMBER OFFSETS
member-list  { START | END } ( LOCAL ) dx dy dz

Where:

ParameterDescription
dx, dy, and dz correspond to the distance, measured in localized or global coordinate system, from the joint (START or END as specified) to the centroid of the starting or ending point of the members listed.
LOCAL optional parameter, if not entered then dx, dy, dz are assumed to be in global. LOCAL means that the distances dx, dy, dz are in the same member coordinate system that would result if the member were not offset and BETA = 0.0.

Description

The MEMBER OFFSET command can be used for any member whose starting or ending point is not concurrent with the given incident joint. This command enables the user to account for the secondary forces, which are induced due to the eccentricity of the member. Member offsets can be specified in any direction, including the direction that may coincide with the member x-axis.

Example of working point (WP) represented by member end offsets

In the figure above, WP refers to the location of the centroid of the starting or ending point of the member.

Example

MEMBER OFFSET
1 START 7
1 END -6
2 END -6 -9

Notes

  1. If a MEMBER LOAD (See TR.32.2 Member Load Specification) is applied on a member for which MEMBER OFFSETS have been specified, the location of the load is measured not from the coordinates of the starting joint. Instead, it is measured from the offset location of the starting joint.

  2. START and END is based on the user's specification of MEMBER INCIDENCE for the particular member.

  3. Local offsets are defined in the local axes prior to rotation when a BETA angle is used.

Parent topic: TR.25 Offset Specifications
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