×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

CMU Height Guidlines for Exterior Walls Bearing at Grade

CMU Height Guidlines for Exterior Walls Bearing at Grade

CMU Height Guidlines for Exterior Walls Bearing at Grade

(OP)
Are there practical or code based height restrictions on exterior CMU walls which are tied laterally at each floor but gravity loaded to the foundation?

Obviously I need to account for floor deflections and thermal movements.

Code or design guide references would be helpful.

Thank you,
Greg

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

(OP)
Good info there but that thread is for a wall spanning a large single story.  Also in that case the wall is load bearing.  My question relates to a wall which is tied laterally at each floor and only supports its self weight, and cladding.

-Greg

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

If it's an exterior wall, and is spanning from floor to floor, I'd use this as a pretty safe guide to wall thickness and height... might change a little, but, not much...

Dik

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

If cladding... then why not use steel studs... likely a lot cheaper..

Dik

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

gregeckel - As mentioned in the last thread there are no limitations on h / t for engineered masonry. Here are the limits using Empirical Design of Masonry - Ref ACI 530 -05:

     Construction                         Maximum l/t or h/t
     Bearing Walls
         Solid units or fully grouted            20
         All other                                     18
     Nonbearing walls
         Exterior                                      18
         Interior                                      36

      t is the nominal thickness of wall.
The code defines wall carrying vertical loads greater than 200 pounds/ft in addition to its own weight as loadbearing.
Many times the thickness of the exterior nonbearing cmu wall used as a back-up is governed by deflection requirements of the finish / cladding /veneer attached to the wall.  

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

Thanks DST... rescued again... I don't have access to my codes, here, but think that even walls (concrete and masonry) designed as slender have limiting h/t ratios... maybe not with ACI... will check, just out of curiosity...

Dik

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

(OP)
Sorry, I should clarify.  In the case I'm considering the floor to floor heights are small (approx 12').  The design of the CMU for out of plane forces is not the primary issue.

The question is about if relieving the CMU is necessary.  For example with brick veneer we limit the maximum unrelieved height.

I.E. Can the wall be built 25, 50, 100 feet tall off the foundation wall without relief?

Thanks,
Greg

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

gregeckel - What is relieving the CMU? Did you mean relieving angles for brick veneer?
dik - Ref ACI 318-05: Commentary R10.8 - Design dimensions for compression members - With the 1971 code, minimum sizes for compression members were eliminated.........  Commentary R10.11.5 - For slender compression members, an upper limit of 100 is imposed on the slenderness ratio if designed by the moment magnified method. No similar limit is imposed if design is carried out according to section 10.10.1 - forces obtained using second order analysis considering nonlinearity.
ACI allows concrete walls to be designed either using provisions of Chapter 10 or Chapter 14. Thicknesses of walls designed using provisions of Chapter 14 shall not be less than 1/25 the supported height or length, nor less than 4". For slender walls provisions of Chapter 10 would apply.
 

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

Thanks...

Dik

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

DST -
The relieving for brick veneer is a practical/detail situation since brick has a long term expansion, while concrete and concrete masonry have a long term shrinkage/creep and steel is just normally creep due to the magnitude of the permanent loads. It is because compatibility of materials to allow openings (doors, windows) to match the exterior.

Dick

 

Engineer and international traveler interested in construction techniques, problems and proper design.

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

You guys are sick, talking about CMU walls relieving themselves.  You really ought to be ashamed.  bigsmile

Mike McCann
MMC Engineering

 

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

I may not be up-to-date on this one, but isn't Ht/150 the service load deflection limit for slender wall design?

LonnieP

RE: CMU Height Guidlines for Exterior Walls Bearing at Grade

I have used publications by the metal building industry to address these kinds of issues. They have these issues when using masonry wainscot walls on metal building since the buildings are generally much more flexible than the masonry. Most of the "relieving" is done with specially designed embed plates and anchor rods that are attached to bond beams or filled cells at top and bottom of the wall and then to the steel frame.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources