ASCE 7 - Table 12.3-3 What is a wall "pier"?

[awa5114]

In ASCE 7-10, Table 12.3-3 it is stated that

"Removal of a shear wall or wall pier with a height-to-length ratio greater than 1.0 within any story, or collector connections thereto, would not result in more than a 33% reduction in story strength, nor does the resulting system have an extreme torsional irregularity (horizontal structural irregularity Type 1b). The shear wall and wall pier height-to-length ratios are determined as shown in Figure 12.3-2."

This is a provision which allows the user to use a redundancy factor of 1 as opposed to 1.3 per the provisions of 12.3.4.2a (Item a).

My question is simple. What is meant here by a wall "pier". Figure 12.3-2 shows is as possibly an integral part of the shear wall but I'm not sure what its role would be structurally. Any ideas or examples of what a wall pier is and what it does? Thanks

 

[SJBombero]

This term is defined in the 2008 Special Design Provisions for Wind & Seismic Figures 4D, 4E, & 4F. "Wall pier" It is also synonymous with "wall segment".

 

[KootK]

Figure 12.3-2 shows is as possibly an integral part of the shear wall

That's precisely what it is. A part of a larger shear wall assembly that has at least one opening in it.

but I'm not sure what its role would be structurally.

It's role would be to help keep the building from flopping over, just like any other shear wall or shear wall segment.

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.

 

[MrHershey]

It's defined in chapter 14 for ASCE 7-05 as a wall segment with a horizontal length-to-thickness ratio of at least 2.5, but not exceeding 6, whose clear height is at least two times its horizontal length. Believe the definition in ASCE 7-10 is the same. Essentially a wall pier is a portion of an overall wall that would have a smaller length:thickness aspect ratio due to presence of openings.

The 'wall pier' concept has actually been around since at least ASCE 7-98 (I think), also has been included in Chapter 19 of the IBC for as long as I can recall. Finally made its way into ACI 318 in the 2011 edition. Essentially requires you to tightens up your tie requirements for smaller aspect ratio (length:thickness) walls. And kicks you into column provisions if you're too small.