FLOOR DIAPHRAGM issues.

Question

Query from: 
 Warning says Zero stiffness in joints 939,940,941,942 which do not exist. The model has been attached where FLOOR DIAPHRAGM command has been used

DSANJU · Accepted Answer

In the attached model the following commands has been used to consider Rigid Floor Diaphragm action: 
 
 FLOOR DIAPHRAGM 
 DIAPHRAGM 1 TYPE RIGID HEIGHT 4.65 
 DIAPHRAGM 2 TYPE RIGID HEIGHT 7.65 
 DIAPHRAGM 3 TYPE RIGID HEIGHT 10.65 
 DIAPHRAGM 4 TYPE RIGID HEIGHT 13.65 
 DIAPHRAGM 5 TYPE RIGID HEIGHT 16.65 
 
 The program is internally creating joints which are treated as master joints. This can be found in the output file: 
 
 The program calculates centre of mass at each floor level. Using joint coordinates of centre of mass it tries to search if there is already defined analytical node at that position. If no user defined node is found at that position, a new joint is created internally. These joints are acting as master joints. Rest of the joints present at that floor will be slave joints. Since these newly created master joints act as orphan nodes and are connected only in ZX, you are getting zero stiffness warning messages for rest of the DOF. This warnings can be ignored. If you want to supress these warnings, you need to add SET PRINT 1 before the Joint Co-ordiante commands. Please refer to the attached modified model.