ETABS SECTION DESIGNER

[saburo]

Hi

I have a query regarding the wall design. I use SD for the wall design(not to design but just check the capacity with given reinforcement). The wall is a C- shape + one of the flanges has a return wall. I have set up spectrum cases in ETABS to design.

Now I have the axial load for EQ and M2 and M3 (given they are properly scaled)for the wall to determine the flexural reinforcement(although these moment may not act concurrently). anyway

I was looking at the results from SD and wondered if we can understand the angles as moment plane. I mean can we get the angle from tan-1(M2/M3) and to see if M2 and M3 are larger than the value from anlaysis, is this OK??

What I found is that for open section if we need to make each direction M2 and M3 working independently under the EQ axial load, alot of reinforcement is needed especially for open side tension. if the moment plane angle is skewed somehow, M2 and M3 are quite easily satisfied.

so my theory is say tan-1(M2/M3)=30 deg
look at 30, 120, 210, 280 and satisfy M2 and M3 capacity concurrently.

Am I right?? Any feedback is appreciated.

 

[StructGen]

Yes Agreed, never used SD with a response case but this is my observation also, when Piers are combined to form one SD section, the capacity increases from 20 to 40%