Concrete Shear Walls

[sdave]

Probably a basic question for many of you but help. Lateral wind forces create moments on the reinforced concrete columns throughout the structure that are excessive. I'm sure I get added shear wall benefit from sections of CBS wall with certain percentage of openings filled with concrete and reinforcement but how do I calculate/quantify this benefit?

 

[ishvaaag]

Then those walls initially meant just for vertical loads (so I interpret) form part of the system that resist lateral forces. By inclusion in the model of such walls you can get appraisal of the influence of such lateral resistant walls in your planned structure. Then as such, follow any particular guide given in the codes for them.

 

[sdave]

Ishvaaag, thanks for your reply and again excuse the novice questions but what do you mean by "inclusion in guides" and "codes" 238? I am using spreadsheet tools to analyze columns and beams. I know how to use code tables for wood shear walls but where do I find something similar for CBS?

 

[ishvaaag]

OK. Prior to the existence of 3D structural analysis software with a graphical interface, life was more complicate (and simple in other ways). To find then how some lateral loads were shared by the structural system was usual by then to find first a center of the weighed stiffnesses present for x and y directions and then find a compatible response for the loading (or something like this). It also had the problem of that this is well suited for a 1 story substructure and even substructures just 2 stories began to be complicated. This surely is because the system was more or less a variation of its simple cousin the stabilization against lateral forces by nonconcurrent 3 vertical trusses. The present possibility of analyzing one model with each member or panel at its proper stiffness where geometrically placed is a convenience that is cozy you use and by making a complete 3D model of your structure, with the proper constraints you plan to be in place, you get a better assesment of the forces in place per hypothesis.

By the way, an incise, center of stiffness, rotation, placement of the resultant at the story with the varying hypotheses continues to be some headache and more than to the user engineer to the houses providing the software for proper analysis since they conjointly complicate the analysis by overspreading attention maybe more than the captured effects are worth, and in my view should be further simplified, even if to the cost of some minimal overdesign.

Then, when I say, follow the guides, or codes, well, the requirements for a wall that just bears vertical load and one that is a shearwall maybe different in the applicable codes. So there is that you need to look at to not forget some interesting clause, detail or explanation.

 

[ishvaaag]

cozy TO use, above, of course

 

[BAretired]

What is a CBS wall?

BA

 

[msquared48]

CBS - channel 7 here.

I beleieve it stands for Concrete Block System.

This could get complicated and your best bet is to retain the services of a local structural engineer.

Mike McCann
MMC Engineering