Shear stud diameter in composite bridge beam

[Brandon]

Designing a steel beam vehicular bridge with a composite concrete deck. Initial run resulted in a W21x68 as the optimal section. However, shear stud design would require rows of (3) 7/8" diameter studs spaced transversely across the beam flange in some locations. The problem is that the flange is too narrow to accommodate three studs. The options are to (a) use 1" diameter studs, which would only require rows of 2, or (b) use a section with a wider flange (a W18x76 tentatively may work).

I think every bridge I have ever seen uses 7/8" diameter studs. Is there a reason I shouldn't use 1" diameter? AASHTO contains no specific provisions related to stud diameter that I can find (other than spacing & edge distance).

Thanks all in advance.

 

[KootK]

I can't think of any reason to shun the larger studs from an engineering standpoint. It might be worth your time to verify that the studs and associated installation equipment is readily available.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[bridgebuster]

Iron workers don't like 1" diameter studs; takes longer to shoot (or for that matter 1" A490 Bolts; takes longer to run up). Can you tighten the spacing to use two per row, or stagger the studs using two per row with one in between?

 

[Brandon]

Thank you Kootk and bridgebuster for your thoughts. KootK, my thoughts were similar, so I am going to do some investigating to see if 1" studs and the proper equipment are readily available. Bridgebuster, the minimum transverse spacing is violated with 3 studs per row, and the longitudinal pitch is already at 6 inches. While this is still (barely) above the minimum of 6d , it is pretty tight and I'd prefer not to go any tighter. Going with a 2/1 alternating arrangement would be worth a look, though.

Thanks again, and any other thoughts anyone has are welcome!