Unique Concrete Shear Wall Shapes

[msegerman]

If I have an arbitrary shear wall shape (e.g., an h-shape) or something similar to that where I have wall segments branching off, are there any limitations on the reinforcement design? I'm designing my wall as an ordinary reinforced concrete wall. I will apply positive and negative moments about each axis. I would prefer to design my wall as a single bending member as opposed to individual rectangle walls. Let me know if you think this is okay or if there are certain things I need to consider such as effective flange widths (for both tension and compression) or additional detailing requirements. Thank you.

 

[johnbridge231]

Your assumptions are ok, one thing should be taken into account only and that has to do with the biaxial bending which occurs due to the arbitrary shape of the cross section. In order to be 100% correct, you should create the corresponding interaction diagrams of the cross section (Axial force vs. Moment about X vs. Moment about Y) recursively and choose a reinforcement amount that satisfies the consdition:

Biaxial forces (2 moments and axial force) vector lies exactly on the interaction surface of the wall. This procedure should be carried out in order to design correctly ecvery element of arbitrary cross sections. Even though the bending can be applied about one axis (uniaxial), bixial bending weill occur due to the eccentricities that are arisen in the analysis.
A software that performs above steps is this one, which i used to work with over the last months.

Regards,

Gigi

 

[msegerman]

Thank you for the response; extremely helpful. I just have a few follow-up questions though regarding the ACI 318-11 code 21.9.5.2 about effective flange widths for special structural walls. Does this apply to ordinary reinforced concrete shear walls? There seems to be very little requirements for ordinary reinforced concrete shear walls. Can an ordinary reinforced concrete shear wall be any shape? Also, the clause states the maximum effective flange width is the minimum of: 1. the face of the web to 1/2 the distance to an adjacent web 2. 25% of the total wall height. I'm not sure if I understand the first part. If I had an "I" section, would that mean the 1/2 the distance from one flange to the other? This statement seems like it would be more applicable to multiple parallel tee beams supporting a one-way slab. Also, the total wall height... I'm still not sure if this means the total wall height for the building, the total wall height from the floor considered to the floor directly above, or the entire total wall height above the floor considered.

Thank you,
Matt, EIT