Masonry free standing wall 6

[Abdel22]

Hi all,
I am designing a free standing reinforced masonry wall( perimeter wall). 12 ft high wall with 5.5 ft wide continuous footing.( L shape due to right way limit)
I checked all stability requirements. Overturning, sliding, soil pressure ,,
And strength of wall and footing
Does it required to have a column for this height or just joint
I appreciate any idea or references
Thank you

 

[Harbringer]

I'm not exactly sure what you are asking but you must design the cantilever wall itself. Stability checks alone are not the only requirement when designing a retaining wall. You need to check/design for the strength of the wall and footing.

 

[Abdel22]

Sorry for confusion..... I designed the wall by itself.( hand calcs and used retain pro) It's a perimeter wall for a site not retaining any soil( like 6 " above footing and 6" behind wall)
One off my colleague bring idea for column at certain spacing because the wall is 12 ft high.
I m not sure if it required to have column at certain spacing due to height

Thanks

 

[dik]

My reply on an earlier thread:

I haven't run any numbers, but for that height I think it will not work (depending on the thickness). You likely need pilasters if you are strictly masonry or steel columns otherwise. Can you 'zig-zag' the wall or serpentine it? to increase the effective 'thickness'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Abdel22]

Its
12 ft high
5.5 ft footing
10 in block
(L Shape free standing wall) at right way line around the site

Any reference or idea appreciated
Thank you

 

[hokie66]

What lateral load are you assuming, or using from a code? What bending moment do you have at the base? What reinforcement are you proposing?

 

[MIStructE_IRE]

10 inch block wall 12 foot high with no piers?

I’d be very surprised if that works.

I’ve done freestanding masonry walls less than half that height that still needed piers.

 

[HTURKAK]

I will advise you to provide RC pillars with spacing 12 ft and RC cap beam (10in X 10 in).. I do not know the applicable code in your zone but to get an idea you may look ;

- Reinforced Masonry Engineering Handbook ( James E. Amrhein, Max L. Porter ) Ch.13 retaining walls
- Building Code Requirements for Masonry Structures ACI 530

Good luck..

 

[phamENG]

I don't think it quite goes into anything as ambitious as your wall, but this document could help guide you and has a bibliography at the end:

NCMA TEK 14-16B Masonry Fence Design

 

[XR250]

I don't doubt you can get the numbers to work out with sufficient reinforcing. However, it may exceed code limits for slenderness. I have ignored that in the past.

 

[Abdel22]

thank you Guys,
just to clarify 5.5ft footing was for shorter section of the wall at the front of the site

Main wall: 12ft high masonry , 10" block
6.5ft wide continuous footing with 2 ft deep and 12"x12" key at middle of footing
use #6 @ 24" vertical reinforcement on stem and #4@ 32" Horiz.

I thought using piers is just another options instead of using continuous footing

just I m not sure about purpose of stiffener column for masonry fence wall (one of my colleagues brought the idea of stiffener column)

hopefully someone who have come cross designing or building masonry perimeter wall can give me some input.

thank you Again

 

[Aesur]

I believe what they are referring to is how the code says cantilever walls shall not have a height to nominal thickness ratio of greater than 6, ie a 8" CMU wall is 4' max, a 10" CMU wall is 5', etc. However, note that this is for empirical design.

Typically the use of stiffening elements, columns, will allow you to design a cantilever column and span the wall horizontally between them as it it wasn't a cantilever wall, thereby allowing for greater height.

If you actually design the wall instead of relying on empirical design you may use a ratio of up to h/t < 30 for slender walls, however axial stress is limited to 0.20f'm; greater than 30 is allowed, but you are then limited to 0.05f'm. Based on this, an 8" CMU wall theoretically can go up to 20' tall, however wind and seismic out of plane loading will require reinforcing such that it's most likely impractical to use 8" at that height. We have successfully achieved 12 to 14' cantilever 8" CMU walls, however the reinforcing was such that it was very difficult to install, with reinforcing each face, every other cell (if I recall correctly). We pushed for using larger blocks for ease of installation, however the contractor insisted on 8". There were numerous issues with installation: dowels sticking out from the concrete grade beams shifted when poured and were therefore no longer sufficient for use as edge reinforcing, other disciplines bent and cut the bars out of the way when it was "in their way", vibrating was difficult with reinforcing each face, conduits were touch to install and others. To fix the reinforcing that was bent/cut/improperly placed we used epoxied rebar, developed into the grade beam which results in staggering the reinforcing each cell, and ended up with a solid grouted wall, it was a mess, but it worked.

This being said, I don't see any major issue with your design if it calcs out.