Pdelta Analysis / Perform Analysis Command

Question

Hello everyone, 
 
 Q1: I want to know whether this format is already correct or not? 
 Q2: After we define the seismic definition, then we start to add Load Case of seismic first.. Does the PDELTA ANALYSIS command should be written in this load case? or PERFORM ANALYSIS ? 
 Q3: To obtain the result of all load cases acting concurrently, I use Repeat Load instead of Load Combination. Does it mean that even we don't use PDELTA ANALYSIS command, we'll get the same result since we already use Repeat Load? 
 Q5: The last command (before FINISH), it should be PDELTA ANALYSIS again or just PERFORM ANALYSIS ? 
 
 Please your kindly advice. 
 Thanks a lot. 
 Really appreciate your help. 
 
 ******************************************************************** 
 DEFINE IBC 2006 ACCIDENTAL 
 SS 0.1 S1 0.3 I 1 RX 8 RZ 8 SCLASS 3 TL 4 FA 1.005 FV 1.43 SELFWEIGHT 1 MEMBER WEIGHT _ROOF UNI 5 FLOOR WEIGHT _ROOFSLAB FLOAD 2.88 ******************************************************************** LOAD 1 LOADTYPE Seismic TITLE EX IBC LOAD X 1 PDELTA ANALYSIS CHANGE 
 ******************************************************************** LOAD 2 LOADTYPE Seismic TITLE EZ IBC LOAD Z 1 PDELTA ANALYSIS CHANGE ******************************************************************** LOAD 3 LOADTYPE Dead TITLE DEAD SELFWEIGHT Y -1 FLOOR LOAD _ROOFSLAB FLOAD -2.88 GY MEMBER LOAD _ROOF UNI GY -5 LOAD 4 LOADTYPE Live TITLE LIVE FLOOR LOAD _ROOFSLAB FLOAD -1 GY 
 *** Then to combine we use Repeat Load instead of Load Combination 
 PDELTA ANALYSIS FINISH

DSANJU · Accepted Answer

You have used correct commands.

DSANJU · Answer

After the load case 1, you should use PERFORM ANALYSIS command followed by a CHANGE command. The same this should be done for the other static seismic load cases. You can find the effect of P-delta for the load combination where you have vertical and lateral load cases combined together- it is to be noted that you should use REPEAT LOAD commands to combine the primary load cases. You are rightly used PDELTA ANALYSIS command.