Problem:

In STAAD module I divide the columns to create a connection later, but iTwin is combining them. How can I create an ISM file without changing the modular geometry (means to keep the member as 2 pieces). In Struclink utility, attribute like  'BREAK_MEMBER_ACROSS' does not break up the member.

Solution:

During ism creation process STAAD checks for colinear beams with the same section assignment and turns them into 1 beam.
In Struclink utility, attribute 'BREAK_MEMBER_ACROSS' works as designed. The attribute 'BREAK_MEMBER_ACROSS' should be assigned to the vertical member to prevent the horizontal member to be exported as full physical member or vice versa.  That's what the attribute suggests.

If there was another connecting member at the intermediate node, and if the above attribute is assigned to that member, then column member would have been treated separately.