F1554 Grade 36, 2 3/4" Diameter Anchor Bolt Capacity 4

[structure_engineer]

Dear Fellow Civil Structural Engineers,

I have to design a foundation for a tall vertical vessels. The anchor bolts designed by the Mechanical Engineers or Vessel Engineers are 2 3/4" diameter F1554 anchor bolts. I am new to this material and thus I need some help to verify if the calculations I did on the anchor bolts capacity are correct and can be used.

AISC Method: =================================================================
Using Section J3.7:
Rn = Fn .Ab
For Ultimate Strength:
where Fn =0.75Fu and for LRFD phi = 0.75
Thus, Rn = phi 0.75Fu Ab = 0.75(0.75)58(pi*2.75^2)/4 = 0.75(0.75)58(5.94) = 193.8 kips

For Allowable Stress Design:
Pa = 0.5(0.75)Ab(Fu) Pg 77 of Steel Design by Segui 5th ed
Pa = 0.5(0.75)(pi*2.75^2/4)(58) = 129.1 kips

As a comparison, the company standard table shows a capacity of 107 kips (Allowable)
The value of 107 kips is obtained as the following:

Rn = Fn Ab Eq. J3-1
Fn = 0.75 Fu
Rn = (0.75 * 58*4.93)/2 (Net tensile area)
Rn = 107.2 kips

I am not sure which is the correct value, the 129.1 kips or the 107.2 kips. I am leaning towards the 129.1 kips as that is based on academic research. The 107.2 kips value is more like based on internal colleague recommendations.

ACI Method: ===================================================================
phi*Nsa = phi*Ase,N *(futa) = 0.75*4.934 *(58 ksi)

Because F1554 Grade 36 is a ductile material, ACI 318-11 D.4.3 says phi = 0.75
phi Nsa = 0.75*4.93*48 = 214.5 kips

Thus, bolt capacity will be the minimum of 193.8 kips or 214.5 kips, for which 193.8 kips governs.

If some of you help to verify the calculations, I could furnish a tabulation of the anchor bolt capacities for the various diameters on here for everyone to use. After all, we need to combine our effort for the good of engineering community for which I believe is one of the purpose of this website. Thank you so much for your attention and effort.

 

[JStephen]

Anchor bolts on vessels and tanks are usually sized more conservatively than ACI allows.
I would view the ACI capacity above as a check on the specified capacity.
It is not uncommon to specify a corrosion allowance on anchor bolts.
It is not uncommon to use 8-thread bolts in larger sizes, which will affect the area.
If I came up with 2-3/4" bolts, I would look at switching to a higher grade.

 

[dik]

Can you see if you can use Grade 55S1? not the unweldable Grade 105, and maybe reduce the diameter a bit? Anchor rod strength and design if very straight forward... I would use the AISC (S16 in Canada) method and maybe check to see if there is a PIP equivalent.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[structure_engineer]

Thank you so much for your time to reply this thread, especially on the weekend.

To go to a higher material grade, I would have to brief my manager on that move. Basically Grade 36 works. My intend is to come up with a consensus on how to calculate the capacity and then share the capacities with the group, for whomever needs them.

Could some of you share your thoughts on my approach? It would also benefit other engineers now that F1554 is becoming more and more common for anchor bolt material. Thank you so much in advance.

 

[le99]

Use AISC ASD - A307 bolt, Fu = 60 ksi:

Ab = 3.1416(2.75^2)/4 = 5.94 in²
fa = 20 ksi
Fa = 20*5.94 = 118.8 kips

or, Fa = 0.33Fu*Ab = 0.33(6))(5.94 = 117.6 kips. <----- Governs.

 

[dik]

I don't like using A307 bolts for anchor rods. Their UTS is 60 ksi and F1554 is higher. Also unless you spec them as weldable, A307 doesn't have to be.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[dik]

I wouldn't normally involve anyone... if an issue, I'd simply advise them that I was using Grade 55S1. That would be the end of it. I design connections for fabricators, these days and often change the spec'd strength to F1554... I often see Grade 36 or A307 spec'd.
There is almost no cost going to the higher grade. For liability reasons, I include that the EOR confirm the use of... I don't want to 'own' the revision.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[le99]

Their (A307) UTS is 60 ksi and F1554 is higher.

How much higher? Compared to F1554 grade 36.

F1554 is an ASTM specification for cast in place anchor bolts. It was established to clarify material properties for anchor rods used in concrete. Prior to it’s creation, concrete anchor bolts were most commonly specified using the generic round bar specification A36 or the headed hex bolt specification A307. The F1554 specification also qualifies two grades in addition to grade 36, grade 55 & grade 105.

 

[dik]

As attached:

75Ksi... I don't know what Grade 36 is, but the cost difference between the two grades is almost nothing.

For 36grade the lowest UTS is 58Ksi... I looked it up...

I always spec Grade 55S1 so it's weldable... I've not used Grade 105. Even if Grade 36 is spec'd I stipulate the fabricator use Grade 55 with the EOR's approval... the added strength is almost free.

...and I never have used ASD for steel, always have used limit states, for over 50 years. Only for the first couple of years did I use Working Stress for concrete. Our steel and concrete courses at the time were all limit state; we were the first year to use them exclusively... back about '65.


Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[BridgeSmith]

2 3/4" seems rather large, and I design highway bridges and high mast lighting towers. If you haven't already, you may want to confirm the availability of anchor bolts in that size. All of our biggest (1 3/4") anchor bolts (rods, actually) are F1554 grade 105.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

Thanks, Rod... I've been using headed anchor rods for over 2 decades, and haven't looked back. I think 1-1/4" is the largest I've ever used, other than some Dywidag threadbars... and other than those, never high strength. With the Grade 105, you may be able to reduce the anchor rods to the size you are accustomed to. 125 Ksi is twice the UTS of the Grade 36.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[BridgeSmith]

I've been using headed anchor rods for over 2 decades, and haven't looked back.

We use the headed anchor rods for traffic railing anchorages; those are 7/8". For the big ones on the high mast lighting towers and large traffic signal structures, we use anchor rods threaded on both ends, with a steel ring at the bottom (nuts above and below the ring). At the top, we have leveling nuts and top nuts. The final torque on the top nuts is about 6000 ft-lbs. The hydraulic wrench they use for that is a beast.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

Much bigger than the stuff I've done... Other than a couple of small pedestrian bridges and a snowmobile bridge, I've never done a bridge.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[le99]

@bridgesmith,

I've seen 3" dia. column anchor bolts at the steel mill, I don't know the grade though.

 

[BridgeSmith]

I'm sure they're made, being available in the location where they will be needed, within a reasonable timeframe and at a reasonable price, is the question of interest, or at least I think it would be.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

OP, you should re-size them using Grade 55S1 to see what you need and compare the two results.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[Rabbit12]

Couple comments.

As BridgeSmith noted, confirm the availability of the anchor in the size AND grade the vessel guys are telling you to use. If you are in a seismic zone and require a ductile failure mechanism, designing anchor reinforcing for a 2 3/4" gr 105 rod will be challenging.

Dik, part of the issue with changing the material/size of the anchor is the equipment manufacturer if a critical piece in this puzzle. They can use any grade of anchor you want, but if they are fabricating the vessel it may be too late to change the diameter.

On tall vessels the anchor grade/size is really something you need to get in front of. I designed a vessel foundation (80' tall/4' diameter) and designed the foundation using F1554 Gr. 36 rods. Just prior to my foundation IFC drawings a reviewer required I change the anchors to Gr. 105. I was locked into the diameter because the vessel drawings had been released for fabrication. My anchor reinforcing consisted of #11 bars to meet the ductile failure requirements of ACI.

 

[le99]

The OP simply is asking to validate his assessment, not looking for ideas.

 

[HTURKAK]

I could not read the previous posts and hope my respond will not be repeat one of them.


- ASTM F1554 is not a material specification,it is an anchor bolt manufacturing specification. There are three materials , ASTM A36/A36M
for low str. requirements , Grade 55 rods for moderate strength requirements, and Grade 105 rods for high-strength requirements...

- ASME ( vessel code ) and API 650,620 uses WSD and the anchor bolts designed by Vessel Engineers ..

- The nominal size of the anchor bolts can be up to 4 in and 2 3/4" diameter is moderate size..

- ASME and API uses effective area ( or root area ) rother than gross area of the anchor rod. The effective area ( Ase= Π/4*(da - 0.9743/nt) nt is , no. of threads per inch. When you look to the following doc. The stress area is 4.93 in**2 for 2.75 in for nom. size..

My suggestion will be, ask the design loads ( wind, seismic, operation, test , empty ..) then design the foundation acc. to requirements of ACI 318 .. and no need to questioning the size of the anchor rods. Or you may prefer to provide more info. to get more specific responds..

My opinion..

 

[structure_engineer]

Hello Fellow Engineers,

I did confirm the 2 3/4" diameter anchor bolt is available. But due to the diameter, a forged head is not available. They could make it both ends threaded and a nut could be tag welded to the bottom of the anchor bolt. I have a quote and just sent back the email asking for the cost for F1554 Grade 36 bolts. The use of higher grade were discussed with the other design engineer. In fact we had agreed on using the higher grade. If the quote comes back with no cost addition it is a no brainer to go with Grade 55.

However, we still have to show in our calculation the actual bolt capacity. And that is the intend of this thread. Could any one of you run some numbers, check my calculations? Your support and attention is much appreciated. At the end of the thread, I could post a table showing the various sizes and the various grades of anchor bolts for F1554.