×
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

ACI 318-11 Special Reinforced Concrete Shear wall minimum reinforcing

ACI 318-11 Special Reinforced Concrete Shear wall minimum reinforcing

ACI 318-11 Special Reinforced Concrete Shear wall minimum reinforcing

(OP)
I have a question on the minimum reinforcing for a special reinforced concrete shear wall. This is a small building (40'-0"x40'-0") so the loads are not very high at all. If I turn to section 21.9 - Special structural walls and coupling beams. I see table R21.9.1 - Governing Design provisions for vertical wall segments. The table specifies when to design the element as a wall or as a wall pier. So for my particular wall in question it is 10'-0" tall and 3'-8" long which gives a hw/lw ratio of 2.72. Walls are 8" thick so my lw/bw ratio is 3.67x12/8 = 5.51. So according to table R21.9.1 my wall should be designed as a wall pier per 21.9.8.1. 21.9.8.1 refers me to sections 21.6.3 - 21.6.5. Section 21.6.3 states that longitudinal reinforcing must not be less than 0.01 Ag which would require 0.01*8*12 = 0.96 sq. in. Definitely does not make sense. Section 21.9.2 is for reinforcing, so does table R21.9.1 not govern for minimum reinforcing? Section 21.9.2.1 states that minimum ratios must not be less than 0.0025 except if Vu is less than Acv*Sqrt(f'c). This is true in my case so I can refer back to section 14.3. I guess it's just confusing that table R21.9.1 seems to require much more steel instead of being listed after section 21.9.2 as an exception. Furthermore, section 21.9.4.3states that walls shall have distributed shear reinforcing providing resistance in two orthogonal direction in the plane of the wall. if hw/lw does not exceed 2, reinforcment ratio pl shall not be less than pt. So this looks like if I use #4 bars then my minimum ratio cannot be less than 0.0020 in each direction? Even though my loads are way below the requirement in section 21.9.2.1. I haven't done concrete shear walls in a while, I have been doing mostly basement walls and grade beam. Just wanted to be sure I was reading all of this correctly.

RE: ACI 318-11 Special Reinforced Concrete Shear wall minimum reinforcing



IMHO, ACI section 21.6.3 is applicable in your case. This section requires longitudinal reinforcement to be in between .01 Ag and .06 Ag, treating the wall similar to a column. Required minimum longitudinal reinforcement, therefore, should be .01*8*(3.67'*12) = 3.52 sq. in. (NOT "0.01*8*12 = 0.96 sq. in.")

On, "I haven't done concrete shear walls in a while, I have been doing mostly basement walls and grade beam."

Reviewing the relevant portions in PCA Notes (sections 21 on 'Walls' and 29 on 'earthquake engineering'), might help you a lot.

RE: ACI 318-11 Special Reinforced Concrete Shear wall minimum reinforcing

(OP)
PSEPK,
My calculation of 0.01x8x12 was for required steel per foot of wall. I did not mean that to be the total steel in the wall, just trying to show why I wasn't sure that 21.6.3 would govern because 0.96 sq. in. per foot of wall is more than (4) #4 bars and more than (3) #5 bars. But I if thats what governs then I'll do it. Just wanted to be sure I was reading it correctly.

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! Already a Member? Login


Resources

eBook - Integrating the Engineering Ecosystem
Aras Innovator provides multiple options for integrating data between systems, depending on the scenario. Utilizing the right approach to meet specific business requirements is vital. These needs range from authoring tools, federating data from various and dissimilar databases, and triggering processes and workflows. Download Now
Research Report - Simulation-Driven Design for SOLIDWORKS Users
In this engineering.com research report, we discuss the rising role of simulation and the paradigm shift commonly called the democratization of simulation. In particular, we focus on how SOLIDWORKS users can take advantage of simulation-driven design through two analysis tools: SOLIDWORKS Simulation and 3DEXPERIENCE WORKS. Download Now
White Paper - Industry 4.0 and the Future of Engineering Education
With industries becoming more automated, more tech-driven and more complex, engineers need to keep their skills and knowledge up to date in order to stay on top of this wave—and to be prepared for the Industry 4.0 future. The University of Cincinnati offers two online Master of Engineering degree programs designed specifically for practicing engineers. Download Now
eBook - The Design Gridlock Manifesto
In this eBook, you’ll learn 6 ways old CAD technology slows your company down and hear how design teams have put those problems to rest. “The Design Gridlock Manifesto” shares first-hand modern CAD experiences from 15 companies around the world. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close