While using the “Master Slave” command to define a rigid diaphragm in a framed multi-storeyed structure, what criteria should one adopt to determine the “Master node”?
For an ordinary static analysis, any of the joints in a master/slave system can be the master joint. A second point to understand about the Staad.Pro 2001 input is that the command SLAVE ZX MASTER j JOINT joint-spec should be used for ordinary floor rigid diaphragms (assuming they are parallel to the ZX axes). This command sets the ZX plane to behave rigidly for inplane actions; while out-of-plane shear and bending will behave flexibly. The command SLAVE RIGID MASTER j JOINT joint-spec should be used if the master/slave connections behave rigidly in all directions and rotations. For a natural frequency calculation and dynamic analysis, the master joint should be the joint nearest to the c.g. of the masses associated with the master/slave joints. If the c.g. is well off the structure as in an L shaped structure with narrow wings, you may want to add a joint at the c.g. just for the purpose of being the master; [remember to connect that joint to another joint with a dummy (low E value) m
