A325 vs A490 Bolts used as a pin.
A325 vs A490 Bolts used as a pin.
(OP)
I have an application where I am overlapping steel plates at a truss joint in a timber truss. I am using a 2" dia. A490 bolt so that the joint behaves like a pinned connection. The nut is shop installed finger tight so the bolt doesn't develop any clamping action.
In this application A490 bolts are used instead of A325 so that a smaller bolt can be used.
Neglecting the cost difference is there an advantage of using a slightly larger A325 bolt instead of a A490 bolt?
In this application A490 bolts are used instead of A325 so that a smaller bolt can be used.
Neglecting the cost difference is there an advantage of using a slightly larger A325 bolt instead of a A490 bolt?





RE: A325 vs A490 Bolts used as a pin.
A 325 bolts are more ductile, if that's of any concern.
Hg
Eng-Tips policies: FAQ731-376
RE: A325 vs A490 Bolts used as a pin.
RE: A325 vs A490 Bolts used as a pin.
Since the major load at this joint is snow the load will be applied gradually without any dynamic loading. Also because the truss has a low span to depth ratio there will only be a very small amount of rotation at the joint.
From college thirty years ago I remember that brittle failures occur quickly. With my joint there is no redundancy, if the 2" bolt fails the truss comes down.
My current field of experience is the design of wood connections so its been a long time since I've worked with A490 bolts. So in working out this design I want to make sure that I am not overlooking something that might cause a brittle failure in the joint.
RE: A325 vs A490 Bolts used as a pin.
Hg
Eng-Tips policies: FAQ731-376
RE: A325 vs A490 Bolts used as a pin.
Just as a point of principle, try to avoid designs where a single-point failure allows the whole thing to fall down.
RE: A325 vs A490 Bolts used as a pin.
Ductility is the ability of a material to absorb plastic deformation or strain before final fracture. Elongation and reduction of area are measures of ductility. Strength is probably the key above because different strength levels can be specified with a minimum elongation requirement.
RE: A325 vs A490 Bolts used as a pin.
Regards,
Cory
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RE: A325 vs A490 Bolts used as a pin.
Even if A325 and A 490 bolts had the same fracture toughness, (which I don't have time to research) you have a lower saftey factor against fracture failure by the Griffith equation if you are applying a higher stress to the A490 than say the A307. You will genearlly be stressing A490's to a higher level or you would just be using a lower strength bolt. In designing pinned connections we we always turn our own using lower strength, more ductile steel, and we retain them with snap rings or spiral retaining rings. Like you said if it fails the whole thing comes down (increase safety factor here). You may also find the 490's to be expensive. I just had a number of 6" dia x 12" pins turned for $130 and 3" dia x 6" turned & plated for $50.
RE: A325 vs A490 Bolts used as a pin.
I have several questions about your use of 6" diam. pins.
1. Do you take bar stock and machine it down to make 3" - 6" pins?
2. Also do you do this in your own machine shop or do you order them from a specialty company like Dyson?
3. Is the $130 amount per 6" dia x 12" pins.
Generally the company I work for, orders all their hardware from a supplier like Building Fasteners or Fastenal. The only time I get involved in ordering, is when an item is a specialty item that our normal suppliers are not familair with.
RE: A325 vs A490 Bolts used as a pin.
Make a drawing of what you want email them for a quote. Send it to more than one shop because they vary widely. Some shops sub out this type of work so they come in higher. Typical tolerance on pins that size is +.000", -.001" on the diameter. If you get it plated spec the OD after plating. Price was each piece.
RE: A325 vs A490 Bolts used as a pin.
RE: A325 vs A490 Bolts used as a pin.
The ASTM A490 specification is limited to bolts between 0.5" and 1.5" (inclusive).
A 2" pin would need a different material specification than A490.
RE: A325 vs A490 Bolts used as a pin.
RE: A325 vs A490 Bolts used as a pin.
RE: A325 vs A490 Bolts used as a pin.
Not true. Fast rates of loading can make steels change from ductile to brittle fractures.
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