Lateral strenght of Post Embedded in Concrete Curb
Lateral strenght of Post Embedded in Concrete Curb
(OP)
How can I determine the horizontal force resistance of the embedment of posts in a concrete curb?
The posts are subject to periodic inadvertent impact from vehicles, and the concrete curb has broken out in a shallow wedge-configuration (I had nothing to do with the original design; it was put in by a contractor based on his own initiative; this contractor does not like engineers).
The posts are 3" diameter galvanized steel pipes embedded 4.5" into an 8" wide curb. This leaves 2.5" of the concrete curb on each side of the post at the post centreline. The posts have no concrete fill in them, but have an aluminum removable cap at the top. The top of the concrete curb is about 6" above the adjacent asphalt paving. I don't currently know how far down below the asphalt that the curb extends, but I may be able to find out from the installer. If the post were a Hilti fastener (or other manufacturer's fastener), I could use their technical manual or software to calculate the shear resistance, but a 3" diameter post is too large to do this.
I could calculate the reaction couple force against each side of the post, for an assumed reactive lever arm, but I don't know where to go from there.
Any ideas?
The posts are subject to periodic inadvertent impact from vehicles, and the concrete curb has broken out in a shallow wedge-configuration (I had nothing to do with the original design; it was put in by a contractor based on his own initiative; this contractor does not like engineers).
The posts are 3" diameter galvanized steel pipes embedded 4.5" into an 8" wide curb. This leaves 2.5" of the concrete curb on each side of the post at the post centreline. The posts have no concrete fill in them, but have an aluminum removable cap at the top. The top of the concrete curb is about 6" above the adjacent asphalt paving. I don't currently know how far down below the asphalt that the curb extends, but I may be able to find out from the installer. If the post were a Hilti fastener (or other manufacturer's fastener), I could use their technical manual or software to calculate the shear resistance, but a 3" diameter post is too large to do this.
I could calculate the reaction couple force against each side of the post, for an assumed reactive lever arm, but I don't know where to go from there.
Any ideas?






RE: Lateral strenght of Post Embedded in Concrete Curb
BA
RE: Lateral strenght of Post Embedded in Concrete Curb
RE: Lateral strenght of Post Embedded in Concrete Curb
We had a problem in our parking area and found the cheapest long term solution was a 12" diameter bored hole 4' deep, filled with concrete and a 4" steel pipe filled with concrete.
A 3" pipe embedded only 4.5" into a curb will never last and remain plumb very long. Even concrete wheel stops in parking lots are anchored more securely.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Lateral strenght of Post Embedded in Concrete Curb
Thanks,
FEM4Structures
RE: Lateral strenght of Post Embedded in Concrete Curb
I had not thought about the post steel expansion that you raise. Since the steel post and the concrete both have essentially the same coefficient of expansion, would this be a problem?
slickdeals (Structural) - thanks for the attachment. I will study it. It seems to deal with my issue.
concretemasonry (Structural) - the vehicles do not include trucks.
FEM4Structures (Structural) - do the AASHO Standards deal with embedment in curbs?
RE: Lateral strenght of Post Embedded in Concrete Curb
Thanks,
FEM4Structures
RE: Lateral strenght of Post Embedded in Concrete Curb
You raise a good point about water finding its way into the recess and splitting the curb apart when it freezes.
In any case, the detail you describe could not stand any significant impact from a vehicle with only 2.5" concrete cover over the pipe. It would need to be much more robust than that.
BA
RE: Lateral strenght of Post Embedded in Concrete Curb
BAretired (Structural)- I am going to try to work out what lateral force it could withstand.
slickdeals (Structural)- looks like a neat spreadhseet. I don't imagin that it is available for use?
RE: Lateral strenght of Post Embedded in Concrete Curb
RE: Lateral strenght of Post Embedded in Concrete Curb
RE: Lateral strenght of Post Embedded in Concrete Curb
Are you able to help me with the following questions with regard to the shop drawing copy of spreadsheet that you sent? I have tried to read it in conjunction with ACI 318-02 but so far have still not figured it all out.
Page 1:
1. I understand where the hef=4.67 comes from (it is 2/3 of 7" slab depth), but where does the 6.25" on the same line, come from?
2. Where does hef=4.5" come from?
Page 2:
3. He seems to be working with a 45 degree breakout cone of concrete(i.e. 90 degrees at the vertex). But ACI says it is a 35 degree cone (i.e. [90-35] x 2 =110 degrees at the vertex). He seems to be using a more conservative model than ACI, but why?
4. Where does the formula for Af = root (bef / d0) come from?
5. Where do the limit Af< 2 come from?
Thanks
RE: Lateral strenght of Post Embedded in Concrete Curb
Are you able to help me with the following questions with regard to the shop drawing copy of spreadsheet that you sent? I have tried to read it in conjunction with ACI 318-02 but so far have still not figured it all out.
Page 1:
1. I understand where the hef=4.67 comes from (it is 2/3 of 7" slab depth), but where does the 6.25" on the same line, come from?
2. Where does hef=4.5" come from?
Page 2:
3. He seems to be working with a 45 degree breakout cone of concrete(i.e. 90 degrees at the vertex). But ACI says it is a 35 degree cone (i.e. [90-35] x 2 =110 degrees at the vertex). He seems to be using a more conservative model than ACI, but why?
4. Where does the formula for Af = root (bef / d0) come from?
5. Where do the limit Af< 2 come from?
RE: Lateral strenght of Post Embedded in Concrete Curb
2. hef I believe is selected by the user.
3. Again not sure
4. This seems to be checking the bearing area. You may increase the allowable bearing pressure if the surrounding concrete bearing area is greater than the contact bearing area.
5. The limit for the increase for the above mentioned increase is 2. (See ACI-08 Sect. 10.14 I think)
EIT
www.HowToEngineer.com
RE: Lateral strenght of Post Embedded in Concrete Curb
RE: Lateral strenght of Post Embedded in Concrete Curb
Unless anyone else has a procedure to put forth. Hard to believe that this issue isn't frequently encountered.
RE: Lateral strenght of Post Embedded in Concrete Curb
These calculations seem to be on the right track, but they are a bit confusing.
EIT
www.HowToEngineer.com
RE: Lateral strenght of Post Embedded in Concrete Curb
Any calc you do will be wishful thinking at best.
As mentioned, corrosion jacking will likely cause it to fail as well.
I would let the Architect put his seal on it.