ETABS Sway Special and Sway intermediate 1

[RSh2]

Hi everyone,
I am designing a concrete building using ETABS 2016, my concrete design code is ACI 318-14 and i have ASCE 7-10 for defining live and seismic loads. after analyse and design procedure there were two beams with (S/O #2) error, because my seismic design category is D all the frames are SMRF (sway special), but when i changed the overwrites for those two beams to (sway intermediate) the error was solved and i got longitudinal reinforcement for these two beams as well, now the problem is solved but i don't know the reason, why was a beam over stressed (o/s) in sway special and not so in sway intermediate???
Hope i have asked the question clearly

 

[NewbieInSE]

Sway intermediate design procedure is different than Sway special. If your structure is in Seismic Design Category D, then you design all your members as sway special. In sway special, for beam, there is beam shear calculation that etabs does based on the section and design reinforcement, by calculating probable moment. The two beams have been probably failing in Shear caused by probable moment. This concept isn't used for sway intermediate beams. You can check out chapter 19, of McGregor's book, maybe "Reinforced Concrete" for more details.

 

[NewbieInSE]

And also know that your problem is not really solved, by getting the two beams passed.
You also have to check Joint Shear, which is another tedious work to do. Beams play lots of roles in smrf design.