As per RCDC requirement, EACH ARM of the Combined wall has to be labelled separately as shown above.

 

• Orange arm - P1; 

• Yellow arm - P1a; 

• Blue arm - P1b; 

• Green arm - P1c.

You can provide the Pier labelling as per your requirement. Above is just an example to show how it should be named.

In short, if you label each arm separately, RCDC will read the geometry and each arm correctly.

Another case where Pier Label needs to be carefully provided is when you Combined wall geometry changes at different levels i.e. the arrangement of Arms of combined wall is changing between different levels --

  

As per above geometry of the Combined Wall, Combined wall is getting split into multiple standalone wall which is supported in the combined wall. 

Ex. Refer to pier label P9 in the Wall geometry at lower level, 

This wall which was a part of the combined wall at lower Level is now a single shear wall at above Level. 

At this point, it is suggested to provide a separate pier label for this wall say 

P9-New1.

Further, maintain this pier label till this wall remains as a single wall only and is not splitting.

The moment this single wall gets split into 2 walls, provide a separate pier label for the 2nd arm of the split wall. 

Few images below for reference :