2.20Partial Releases

Frame members are assumed to have complete continuity at their end joints (rigid joints) so that the bending moment at the joint is fully transferred to the other connecting members based on their relative stiffnesses. There are cases, however, when the connection may not be able to develop full continuity of the connecting members, or when the moment at a connection must be distributed to the connecting members in specific pre-determined ratios.

 

Figure 2.10 Member-end Releases

Such cases can be modeled by assigning a release factor at either or both ends of a member to specify its continuity or how much moment release should be allowed at its end. The release factor can be any value between 0 and 100, where 0 denotes a fixed end condition and 100 denotes a hinged end condition. A fixed member end (release factor equals 0) allows distribution of the moment at the joint to the connecting members based on their relative stiffnesses. A hinged member end (release factor equals 100) allows free rotation of that member at that end and no moment will be transferred to the connecting members. A partially released member end (release factor greater than 0 and less than 100) allows some rotation of the member at that end and the specified amount of moment will be released to the connecting members