clarifications master-slave vs. retained/constrained

Question

Hi there, 
 I noticed that in v15.0 the name of master-slave has been changed to retained/constrained in Precede. Could you please kindly confirm the following questions? 
 
 1. iIs master-slave being made obsolete and replaced by retained/constrained joint? 
 2. if yes, is retained/constrained working the same way as master-slave? 
 3. I read in the manual SACS 15 for retained/constrained that "coupled joints should not be coupled for all degrees of freedom, typically. distinct points may be forced to displace similarly but may not rotate similarly." what is the consequence if I restrain for all DoFs? 
 4. Analysis with master-slave script sill can be run successfully in SACS 15.0 , but there is no line assistance in datagen for master-slave. is this correct? 
 thanks in advance. 
 
 Kind regards, 
 Jacqueline

SWARUP Selvaraj · Answer

Dear Jacqueline, 
 Master-Slave is completely different from Retained Degrees of Freedom. In any static structural analysis , the pre-specified displacements/rotation of the master nodes are transferred to the slave nodes when we define Master-Slave relationship between nodes. Usually, it is used to simulate diaphragm action of non-modelled deck slabs , to ensure rigid body motion of the secondary beams supporting the slab. Retained degrees of Freedom is used for arriving at the mode shapes during the natural frequency estimation phase of any dynamic analysis . Out of the six degrees of Freedom (dx, dy, dz, rx, ry, rz) for each node, mode shape will be generated only along the retained degrees of Freedom. For instance, if node "0000" has a boundary condition of " 222000 " then there will be only three mode shapes (displacement along X / Y / Z axis) for the node "0000". Selection of the right Retained degrees of Freedom is essential to achieve the desired Mass Participation factor during a dynamic analysis . Thanks and Regards, 
 SWARUP Selvaraj.

Vul Thang · Answer

iIs master-slave being made obsolete and replaced by retained/constrained joint? 
 
 Yes, it is being replaced by Retained/Constrained. 
 
 if yes, is retained/constrained working the same way as master-slave? 
 
 Yes. It works exactly the same, just the naming is changed. 
 
 I read in the manual SACS 15 for retained/constrained that "coupled joints should not be coupled for all degrees of freedom, typically. distinct points may be forced to displace similarly but may not rotate similarly." what is the consequence if I restrain for all DoFs? 
 
 SACS just provides you suggestion. Depending on your structure or the way you like to restrain, SACS gives you the option to restrain all degrees of freedom. Please refer to Section 2.8.2.5 Retained Degrees of Freedom in SACS IV manual for full information. 
 
 Analysis with master-slave script sill can be run successfully in SACS 15.0 , but there is no line assistance in datagen for master-slave. is this correct? 
 
 Please rename MASTER to RETAIN in Data Generator manually to see the Line Assistant. This will be updated in future release. Please also refer to SACS IV manual for the RETAIN card for detailed information.