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Reinforced Concrete Shearwalls

Reinforced Concrete Shearwalls

Reinforced Concrete Shearwalls

(OP)
I just found out that I blew the reinforcing steel budget for a project, and it's because I have very heavy bending reinforcing at the ends of my shearwalls.  Does anyone know of an economical method (that's not untested) besides rebar to get the needed bending capacity from a shearwall?  How about a vertically posttensioned shearweall?

RE: Reinforced Concrete Shearwalls

Why is there so much bending in this shear wall? By definition, shouldn't the concrete in the shear wall handle the shear forces? Ideally, the length of the wall should be parallel to the shear force being resisted. When this is the case, flexural reinforcement would be the minimum required.

Am I missing something here?

Matt

RE: Reinforced Concrete Shearwalls

It is unlikely, pst-tensioning should out of higher technology be dearer for most cases, except maybe for slabs where such is the common practice, which is not your case. So, better add shear wall.

RE: Reinforced Concrete Shearwalls

For shear wall you do not need to have all reinforcement at ends of wall. You need to consider all vertical reinforcement as flexural reinforcement. It will reduce your end reinforcement big time. You may use PCACol software or do it by hand, follow Example 4 of "Seismic Design Manual" Volume III by ICBO and SEAOC.

Good luck.

If you need help, let me know.

RE: Reinforced Concrete Shearwalls

concrete shearwalls, in tall buildings, are essentially large vertical cantilever beams. so yes they require reinforcing at their ends for tension and compression as well. the closer you get to center of the shearwall the less effective the vertical reinforcing become.

postensioning is not economical and definetly not practical in the field. generally, you will have to deal with cable mechanical splicing devices that will replace a large area of concrete that is needed the most at the wall end for compression resistance.

RE: Reinforced Concrete Shearwalls

PCI has precast post tensioned shearwall info....shearwalls in seismic areas need the toughness of A706 reinforcing in their chords...i wouldn't think p/t strands have nearly enough ductility.

RE: Reinforced Concrete Shearwalls

(OP)
The building I'm talking about is a 13-story building with very tall ceilings.  It has the height (and hence the wind pressure area) of a 17-story, but only the self-weight of a 13.  It's in a hurricane-prone area so the wind is very significant.  That's why I have so much bending.  I thought maybe someone had heard of a new method to use besides huge amounts of rebar at the ends.

RE: Reinforced Concrete Shearwalls

BrassFox,

I agree with V2.  Reinforcing steel is required, and should be located closed to the ends of the wall.  See "Notes on ACI 318", a publication of the PCA, for a very detailed example of a shear wall design.

The two ends of the wall may be returned, forming a C or a I shape, to increase the "d" of the wall.   Additional reinforcing may be placed in the returns.

I do not believe prestressing would be economical, unless the width of the wall is limited.   Do not forget to check the deflection of the wall.

Hope this would help

AEF

RE: Reinforced Concrete Shearwalls

BrassFox

Instead of using solid concrete walls you might consider to go with polysteel walls. Polysteel walls are essentially concrete shear walls, looks like vertical waffle slab. I recently designed two buildings using polysteel walls as shear walls. These walls are both cost effective and energy efficient.

You may check with the polysteel.com for detailed info

RE: Reinforced Concrete Shearwalls

Can you reduce its dimensions increasing lateral deformation of the building?

by doing that you also distribute horizontal forces a litle more to the remaining collumns...

RE: Reinforced Concrete Shearwalls

sorry... stupid idea!

I was thinking of Seismic not Wind...

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