A307 vs A325 bolt 4

[upk]

About 3 years ago while casting the upper part of a building. I asked in this forum whether to use A307 or A325 bolt for future roofing addition. Someone recommended A307 over A325.. I couldn't find the thread pertaining to it and the exact reason but it's something along the line of the A325 being high strength and more brittle in connections.. so I used A307. But reviewing their strength now.. I seemed to regret choosing A307.

I'd like to know what application do you exactly use the A307 bolt over A325? Does the A325 require special torqueing in the nuts or longer embedment length.. is there special reason to use the A307?

 

[CANPRO]

is this loading low or big?

Can you specify the loading? I'm confused by this thread and your line of questioning. Who specified these bolts in the first place? Are you responsible for determining if these bolts are adequate? I mean this with all due respect - based on this thread, I don't think you're qualified to make these decisions.

 

[upk]

Ron.. many said they never use A307 and some use it only on wood.. so I presume they are so poor.. i'll add hilti chemical anchors on the column top...

the designer who specified the A307 already resigned and the contractor is hurrying to put the metal plates.. so I have less than 12 hours to get all the Hilti chemical bolts and install them myself noting of the breakout, pryout, and tension cones failure mode with coordination from Hilti engineers...

 

[hokie66]

Whatever you interpreted to mean the A307 bolts are "poor", forget it. Read Ron's post and take it as gospel.

Until very recently, A307 was the most commonly used grade for anchor bolts. Perhaps it still is.

High strength anchor bolts should only be used when you really need the strength. They are less ductile, more expensive, and generally less available.

What size are your existing A307 anchor bolts and what force do they need to take? Until you can answer that question, you have no basis to change anything.

 

[kgengr]

A307 is standard for steel to steel bolted connections in our office unless higher strength are required.

 

[RPMG]

A307 was used for cast-in-place concrete anchors until recently. It's yield stress is assumed as 36 ksi.

Now, the common cast-in-place anchor is F1554, where the yield stress is specified as 36 ksi.

Do not use A325 for anchors. If a higher yield stress is required, there are higher grades of F1554. I think I remember them being 55 ksi, and 105 ksi.

 

[upk]

How much can the end of the A307 be hammered before it loses strength? After the contractor measured the hole positions by putting the blank plates on top (drawing with pencil around the cast-in-anchor end see picture above) and after we bring it to shop to be drilled.. the drilled holes can't aligned with the anchors exactly... so can we hammer the A307 end (with a nut put into it and hammered to avoid thread damage)? Hole drilled is 17mm.. anchor is 16mm

 

[JStructsteel]

I would not let them hammer the bolt at all. Drill the correct spacing, and use oversized plate washers.

How much moment are you trying to resist at this connection, that will help us all out give you better advice.

 

[upk]

I would not let them hammer the bolt at all. Drill the correct spacing, and use oversized plate washers.

How much moment are you trying to resist at this connection, that will help us all out give you better advice.

Only very few moment.. it's just to support rafter at middle.. it's mostly on shear when rafters flex during seismic.

 

[JStructsteel]

So what are the calculated values, Mu, Vu?

 

[upk]

actually the designer ignored the poor A307 that's why he made the base plate smaller enough not to use it.. but contractor use bigger plate that uses the A307.. and designer said no problem... So we'll end up with 8 bolts per 500x500mm base plate.

Isn't it A307 is supposed to be soft.. can it suffer fracture by just little blow to align with drilled holes?

 

[JStructsteel]

Yes, its poorly soft. Dont hammer it. Drill the holes out, and use bigger plate washers.

 

[upk]

If hole is bigger.. and the structure sways back and forth.. then the increased hole may even cause enough inertia and momentum to even strain the bolt.. no?

 

[JStructsteel]

im pretty sure if your structure sways that far, the bolt is the least of your worries.

Where is this structure being built?

 

[upk]

Seismic zone.

In grade 40 rebars.. you can bend it more to be used as stirrups.. the grade 60 rebars can just fracture.. in the case of the A307.. it's grade 37.. won't it be flexible at all? why?

 

[JStructsteel]

Thanks. Good luck with your structure.

 

[upk]

Thanks for this tips about the A307 being poorly soft jrisebo. I just called the contractor now and demand they don't hammer the bolt because it's "poorly soft" and instead make the hole bigger like you said on at least one of the holes and use washer.

About the designer. He was just 22 years ago and no field experience. When I asked him details like this last time. He said his job was only to produce rebars output ratio and it is up to the contractor to implement it. So I know I need to first check the background of the designer before giving him any project.

 

[JAE]

I posted this in your other post - but A307 was used for years as anchor bolts (rods actually).
You would never use A325 for embedded anchor bolts.

Currently F1554, Grade 36 (or 55) is the proper anchor rod specification.



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[upk]

In the Philippines. All use high strength A325 in wide flange columns.. they have to let the fabricators produce them for any length. This is according to my contractor and designer. They ask why I used such lowly A307. This is what prompted me to ask all this. I went to a hardware this morning. Their A325 are only short and like a big screw. Maybe when the A325 are made into long anchors.. they become another name? What is the new name or is it still A325?

 

[Surya77]

@upk

A325 are high strength bolts, they cannot be used as anchors

per AISC, preferred anchor bolts are F1554 gr 36, Gr 55

They cannot be called with different name to make it anchors. A325 chem composition is different from F1554

 

[TLHS]

I still call out A307 on occasion because there's one location nearby where, for some reason, finding all thread F1554 rod without getting it threaded to order is hard (or the contractor in that location is just bad at finding things and likes paying steel fabricators to custom fab anchor rods?). So for small, non-critical projects there I'll often call out A307.

There's absolutely nothing wrong with A307 as an anchor rod, especially when you're so close to the edge of the concrete that you're unlikely to be able to develop the strength of the rod anyway.