Bolt clearance 2

[JStructsteel]

Got a W8x10 bolted down to another beam. Gage is 2.25" and Im using 3/4" bolts. Seems very tight.

What is the gage set for, up to what size bolt?

 

[WinelandV]

From the SCM, Part 1 (page 1-3 in the 15th Ed.):

"The term workable gage refers to the gage for fasteners in the flange that provides for entering and tightening clearances and edge distance and spacing requirements. When the listed value is footnoted, the actual size, combination, and orientation of fastener components should be compared with the geometry of the cross section to ensure compatibility."

Please note that is a "v" (as in Violin) not a "y".

 

[JStructsteel]

So basically use the working gage unless you cant tighten it, or it interferes with the radius of the section, etc.

you can use a different gage and not get in trouble with the detailing cops?

 

[DrZoidberWoop]

It's not going to be possible to get a gun on the head/nut that's next to the W8 web.

But hey, maybe this isn't even technically a structural application and you don't have to pretension.

Another red flag that I see is the edge distance.
A W8x10 has a 4" wide flange, so the edge distance = (4-2.25)/2= 0.875" < 1" min from AISC Table J3.4.

 

[DanKile]

Probably 5/8" bolt with the standard edge distance. 3/4" bolt standard edge distance is 1". You can go less, but you need to check it more closely.

The 3/4" bolt head or washer might be getting into the fillet of the W8x10. I remember seeing where overlapping the fillet a small amount is ok. I was looking for that reference recently, but couldn't find it.

 

[JStructsteel]

Thanks. Yes, these are not pretensioned. I more than likely will just goto a W8x18 beam to get more clearance. They could possibly get them with a wrench no problem though.

 

[XR250]

Why not just use a 1/2" bolt?

 

[cliff234]

XR250 – To enhance constructability, if the fabricator is using ¾” bolts for all connections (a common bolt size), it would be best to use ¾” bolts for the connection in question. You don’t want to have (5,000) ¾” bolts on the project and only (4) ½” bolts. Just use a W8 with a wider flange. In general, when we have bolts in the flanges of W shapes (for flange plate moment connections), I always encourage using at least a W14x22 (with a 5” wide flange). You can easily install 3/4” bolts in the flange of that beam. I’ve seen projects where there are lots of short stubby beams cantilevering off perpendicular spandrels and the engineer shows W8x10’s, W10x12’s, and W12x14’s (all with 4” wide flanges) because the moments are very small. The problem is it is impossible to put flange bolts in those beams. Just use W14x22’s. Engineers often try to shave every last pound of steel off their project. AISC has espoused for years the saying, “Least weight is not always least cost.” This is an example where using a slightly heavier beam will enhance constructability.

 

[dvd]

These might be helpful - clipped washers

 

[XR250]

To enhance constructability, if the fabricator is using ¾” bolts for all connections (a common bolt size), it would be best to use ¾” bolts for the connection in question.

Makes sense for a big job but this job may be 2 beams total. I guess the OP needs to chime in.

 

[ProgrammingPE]

There's 3 distances you need to concerned about when locating a bolt in a flange (using W8x10 w/ 3/4" Φ bolts in calcs below):

1. Minimum edge distance per Table J3.4
Edge Distance = (bf - g)/2 = (3.94" - 2.25")/2 = 0.845" < 1"
Section J3.4 says "The edge distances in Table J3.4 are minimum edge distances based on standard fabrication practices and workmanship tolerances". This means there's some flexibility here, but it's not clear how much.

2. Clear distance to the web - C1 per Table 7-15
Clear distance to web = (g - tw)/2 = (2.25" - 0.17")/2 = 1.04" < 1.1875"
C1 is the distance required to get a socket around the bolt or nut. It is equal to half the socket diameter of 2-1/8" plus 1/8". If this isn't met, then it may be possible to use wrenches instead.

3. Clear distance to the beam fillet - C3 per Table 7-15
Clear distance to fillet = g/2 - k1 = 2.25"/2 - 0.5" = 0.625" < 0.75" for circular washer or no washer or 0.6875" for clipped washer
If this isn't met, the washer (or nut if there is none) will no longer be bearing on a completely flat surface so you may be inducing some flexure in the bolts or creating local points where the bearing stress is exceeded.

Using 5/8" Φ bolts with clipped washers or a beam with a wider flange is likely a better option since 3/4" Φ bolts don't meet any of the critical dimensions here.

The 3/4" bolt head or washer might be getting into the fillet of the W8x10. I remember seeing where overlapping the fillet a small amount is ok. I was looking for that reference recently, but couldn't find it.

You might be thinking of Figure 10-3 which allows the free edge of plates or angles used in web connections to encroach on the fillet. They likely have a higher tolerance for some offset, though, since the free edge can bend out of plane, still leaving the area directly below the bolts flush. The bolts must have a flat surface so the values for C3 do not allow for any encroachment.



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[JStructsteel]

I actually had it 1/2" bolts, but since all other connections are 3/4" the client wants to use 3/4". Im just going to upsize the beam.

I think 3/4" would work, but to follow the rules I wont create an issue for the erectors.