Can etabs design box shaped shear walls? 3

[Shahin]

Dear friends, I have a box shaped shear wall in my building and I have faced a problem about designing it. I assigned all 4 walls in one pier and used section designer to model the wall and assign bars to the wall. According to etabs manuals etabs can design U,L,T shaped shear walls but I don't know if etabs can design box shaped shear walls or not. On the other hand, Should I assign my shear wall with a combination of a U shape and a single wall or I can simply assign all 4 walls in one single pier and design it with one section defined in section designer. Your help is highly appreciated.

(Note: I have an openings in one of the walls but its size is negligible comparing to the size of the shear wall.)

 

[ASCE07]

Please assign each wall as a separate pier.

 

[zeemas]

As ASCE07 suggests to assign each wall as seperate pier I will say the same for design of piers.. I am not sure about ETABS design for box shaped shear wall, even i will not suggest to do that for U, L or T shaped shear walls because of ACI clause 21.9.5.2 (as this clause says "Unless a more detailed analysis ......" still I dont know what does ACI mean by saying MORE DETAILED ANALYSIS.....). So to be very brief assign seperate pier use section designer to determine reinforcement, and boundry elements and put little more efforts in details.

Any comments are welcome.

 

[structuresguy]

Well, I would take the opposite approach and recommend that you assign one pier label to your box. According to their manual, online videos I have seen, and conversations I have had with their tech support, the section designer takes into consideration the section properties of the overall shape you define, be it box, L, T, etc.. It then uses these section properties when considering the total loading it sees from the various pieces that make up your section.

As you will really have a box section, it makes sense to take advantage of it's section properties. Otherwise your design will be overly conservative, in some cases extremely overly conservative.

You can always do some simply hand calcs to verify the reinforcing. You shear will be resisted by the side walls in shear, and the overturning moment by the end walls in C/T. Once you work out what net tension you have, if any, you can verify your tension reinforcing in the end walls. You will likely find that minimum steel will cover most overturning requirements, unless you have very tall and slender box.

One concern that you have to consider is the shear transfer from wall to wall at the corners. You will need to ensure you have adequate horizontal corner reinforcing to resist the shearing. Also, the configuration of your openings may affect the behavior of your section. For instance, door openings at one side of a box in the corner may prevent the shape from acting like a box, due to the weak plane at the corner. In this case, I would look at it like a C shape.

 

[zeemas]

Any comment about ACI clause???
How we will justify this?

Any idea what do they mean by MORE DETAILED ANALYSIS?

Thanks

 

[prsconsultant]

Completely agree with structuresguy. ETABS design for core walls (box) would be much more efficient than the code approach of using effective flange widths.

 

[structuresguy]

I would say that any 3D FEM based analysis would satisfy the requirements of the Code to provide a MORE DETAILED ANALYSIS. My interpretation is that they mean more detailed than simple 2D compression-tension type analysis of the wall.