Shear wall considered as moment frame 1

[bensarengat]

Hello,

I`ve got a project that only allow me to put some shear walls in one direction (say Y direction).
My intension is to design the building as dual system in Y direction, but special moment frame in X direction, despite some girders connected to shearwall`s weak axis. Is that legit to considered shearwall in weak axis as column (therefore i could make it as special moment frame).
As we know that seismic reduction factor is diffrent between dual system and moment frame.

thank you, hope you guys can help me.

 

[bensarengat]

According ASCE 7-10 R for dual system is 7 while special moment frame is 8.
My project is reinforced concrete building.

 

[JAE]

I'm not sure how you combine a shearwall (as a column) with a fixed steel beam connected to it and enter the charts with a concrete/steel combination moment frame. The concern would be the durability and ductility of the connection between the beam and "wall-serving-as-a-column". That configuration isn't a "dual" system by the code I think so you'd have nothing to base the design on.

I suppose you could use the lower R of a steel moment frame vs. a concrete moment frame and go with that.



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[KootK]

I'm going to assume that:

1) We're talking about concrete members for everything here.
2) You're actually planning to have moment frame beam hinges form at the face of the concrete walls.

With that in mind, here are my thoughts:

1) In principle I'm okay with it.
2) You'll need to design your wall convincingly so that it won't yield before the beams form plastic hinges.
3) Whatever you do to the walls to make them work for #2 may affect your over-strength wall flexural capacity in the other direction.
4) If you have to consider a non-orthogonal lateral load case, and I suspect that you do, the accounting associated with looking at the wall for bi-directional lateral load will be a nightmare.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[JAE]

"We're talking about concrete members for everything here."

I think you may be right - I probably misunderstood the OP

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[bensarengat]

thanks JAE & KootK.
You`ve got the point about beam hinges moment frame. I just doubt that the wall and beam combination could be considered as special moment frame instead of dual system (walls + frame).
I`ve applied earthquake load in orthogonal direction + rendundancy factor (1.3) + Vertical seismic load (DL + 0.2SDS)
the rebar is pretty crowded, it reach about 3% ratio.

 

[serrojo]

Hi,

I think you could enlarge the wall´s thickness at the pier legs that way you could direction the efforts to the Piers and your wall in general will be lighter in rebar.

The second thought is about your floor elements, you could use ribbed slabs to distribute evenly the efforts in the weak direction, there is no need to concentrate everything on edges of the wall.

Hope you could figure it out!

Regards,



MSc. Eng. Serguei Joa
Tel: +5352460358
mail: sm.joa@bouygues.cu