Query Description:
Difficulty for matching the Moments for a Beam in ETABS vs the same Beam in RCDC even when same Load Combinations are used while designing.
Details on RCDC working:
The critical forces that are identified in ETABS is for the Combination which has Dynamic EQ and for the same, the StepType = Min.
The Step Type Min and Max happens internally in ETABS where the Dynamic Load case gets Added and Subtracted in the Load Combination with other load cases.
Explanation with an example:
Below is the load combination that is defined in ETABS.
| Load Comb 1 = 1.5 (DEAD) +1.5 (PARTITION) +1.5 (SDL) +1.5 (SPECX) |
When the forces for this combination is stored it happens in 2 Steps which is
StepType = Max
and
StepType = Min.
Further, the Step creation and the calculation happens internally within ETABS.
Now, To replicate the same condition in RCDC as well, we suggest you at add additional Load Combination where the SpecX will get Subtracted from the load combination. The load combination can be as follows:
| New Combination = 1.5 (DEAD) +1.5 (PARTITION) +1.5 (SDL) -1.5 (SPECX) |
By doing so, the forces will get calculated exactly as what happens in ETABS while designing.