Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

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

Thru-Bolt Concrete Anchor Shear Breakout Capacity

Status
Not open for further replies.
P1ENG

P1ENG

Structural
Aug 25, 2010
237
Let's say I have 3" of 5000 psi concrete (3" topper of a 6" thick deck), such that le=da=3". I want to put plates on both sides and bolt through the concrete with 3/4" A36 rod to connect the plates. The closest edge distance is 20.5" (ca1). I am using ACI 318-14. Avco (17.5.2.1) is very large because of the large edge distance and Avc is very small because of the 3" thickness. So my Avc/Avco = 0.098. Vb (17.5.2.2) is equal to 52.5 kip [9*sqrt(f`c)*ca1^1.5 -OR- 7*(le/da)^0.2*sqrt(da)*sqrt(f`c)*ca1^1.5]. My Vcb ends up being 5.12 kip. This seems pretty small for such a large edge distance. Am I missing something? Am I shooting myself in the foot by only using the continuous 3" thickness of the topper? There is WWM in the topper, should I be including that somehow?

It is a little crude since it is preliminary, but below is my math.
Capture_m9w1hm.png


Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant
 
Replies continue below

Recommended for you

Sort by date Sort by votes
I see that through-bolts are excluded from Chapter 17 (17.1.2) thanks to reading this post:
So now my question is, how do you check the shear capacity of a through-bolt?

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant
 
Upvote 0 Downvote
usually if possible we use a shear key for the shear force and not the bolts
unless the shear force is 'small'





best regards
Klaus
 
Upvote 0 Downvote
klaus,

We are tieing a construction elevator to the building's floor. We have no control over the concrete, but we do know what it is. I have about 10.72 kip of resultant shear (9.42 kip towards 20.5" edge, 5.13 kip parallel to edge) and my client's typical anchorage is (2) 3/4" A36 rods through sandwiched plates. Tension is only 1.7 kip. Threaded rods are 6.5" apart and the parallel-to-edge force has a line of action through both bolts. AISC bolt shear analysis tells me A36 rods are good for 11.5 kip total [5.75 kip per rod], so I don't have enough shear capacity remaining to pretension the bolts to gain frictional resistance. This leaves me with relying on the bolts to bear on the concrete. I can check the concrete shear capacity (conservatively assumed unreinforced) as shown below.

I know concrete is LRFD, so the below is a quick check of my ASD load vs. an ASD allowable concrete shear using the known AISC LRFD:ASD relationship between omega and phi.
Capture_yj08sx.png


Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

BridgeEngineer21
  • Question
Concrete edge (breakout) failure in shear on anchor group - Eurocode 1992-4 vs ACI 318 2
2
Replies
21
Views
4K
BridgeEngineer21
BridgeEngineer21
DTS419
  • Locked
  • Question
Concrete Strength for Thru-Bolt Connection 1
Replies
6
Views
545
TLHS
TLHS
Dam lover 68
  • Locked
  • Question
Concrete breakout resistance of anchor in tension
Replies
3
Views
467
TLHS
TLHS
EngDM
  • Question
Breakout of I-Beam Cast in Concrete 1
2
Replies
25
Views
3K
TLHS
TLHS
JStructsteel
  • Question
Deep embedment of anchor for capacity
2
Replies
20
Views
5K
XR250
XR250

Part and Inventory Search

Sponsor

Back
Top Bottom