Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Overstrength factor with foundation for Cantilever column

Phatt

Phatt

Civil/Environmental
Mar 25, 2022
6
Hi everyone,

I’ve been reading ASCE 7-16 and I’m currently working on a cantilever column system assigned to SDC C or higher. I have a few questions regarding the use of seismic loads with the overstrength factor (Ω₀). From what I understand, the overstrength factor must be applied when designing the connection, base plate, and anchor bolts, as per ASCE 7.

Here are my questions:

  1. Should we also apply the overstrength factor for overturning, sliding, and soil bearing checks?
  2. For a pier footing foundation, do we need to design both the pier and footing using the overstrength load?

    1744988945152.png


  3. For a single pile foundation, is it necessary to design the pile with the overstrength factor, or is it sufficient to apply it only to the anchors?1744988992485.png

I’ve read the following references, but I’m still unclear about how the overstrength factor applies to foundation design in particular:

Thanks in advance!
 

Attachments

  • 1744988800679.png
    1744988800679.png
    152.3 KB · Views: 0
Replies continue below

Recommended for you

Sort by date Sort by votes
The last sentence of 12.2.5.2 i believe has your answer. Foundation and other elements used to provide overturning resistance at the base of the cantilever column elements shall be designed to resist seismic load effects including overstrength.

In my view the answer to all of your questions is: Yes

In general to my knowledge the only foundation elements requiring overstrength are for cantilever column systems.
But anchorage to concrete is often designed for overstrength based on ACI requirements for seismic zones.
 
Upvote 0 Downvote
Phatt said:
Should we also apply the overstrength factor for overturning, sliding, and soil bearing checks?
Click to expand...

Yes but IMO ,except sliding.
The commentary of clause 12.2.5.2 ,
***********
C12.2.5.2 Cantilever Column Systems. ..... Because the ductility of columns that have large axial stress is limited, cantilever column systems may not be used where individual column axial demands from seismic load effects exceed 15% of their available axial strength, including slenderness effects.
Elements providing restraint at the base of cantilever columns must be designed for seismic load effects, including overstrength, so that the strength of the cantilever columns is developed.
***********
My interpretation , the primary restrain is bending . The relevant design checks basically overturning and so bearing.
The other questions , my respond will be Yes.
 
Upvote 0 Downvote
You must log in or register to reply here.

Similar threads

L
  • Question
Column Design for Earthquake Loads According to ASCE 7
Replies
1
Views
3K
HTURKAK
HTURKAK
FOX89
  • Question
Strong column weak beam - SCWB
Replies
6
Views
6K
HTURKAK
HTURKAK
KevinNZ
  • Locked
  • Question
ASCE Ra values for pile and slab foundation
Replies
3
Views
867
HTURKAK
HTURKAK
Luceid
  • Question
Boundary Zones for Core Walls
Replies
1
Views
1K
HTURKAK
HTURKAK
nategemb
  • Question
Seismic Loads for Cranes
Replies
3
Views
2K
HTURKAK
HTURKAK

Part and Inventory Search

Sponsor

Back
Top Bottom