What "GAGE" stands for in AISC? 1

[pplbb2011]

In AISC manual for steel section tabke, "gage" is defined as for the bolt hole spacing at steel flange, is this value the minimum spacing when bolt hole is drilled in both side of steel web? Can the bolt hole be drilled less than "gage"?

 

[jimstructures]

I hope somebody will correct me if I get this wrong and it is completely from memory. Gage is measured across the member or web and pitch is measured along the member or web.

So if you have four holes laid out symmetrically at one end of a member the gage of the holes is across the the web and the pitch is along the web or the repeated spacing along the web.

Hope this helps.

Jim,

 

[Qshake]

Generally speaking the bolt hole cannot be drilled less than gage. This distance defines the least dimension required to get a machine tool to properly drill out the hole or, of equal importance, a air-wrench or spud or socket to tighten the bold/nut. If you can't tighten the bolt, it won't do much good to drill a hole. Other dimensions you need to be careful of are making sure you can get a washer and nut in place. Especially since the washer is larger than the bolt head or nut. This is especially noteworthy in re-entrant corners. There are field modifications such as grinding the washers flat on an edge or cutting them but if you have a lot of them no ironworker wants to be grinding/cutting forever.

I hopet this helps.


Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[jnich]

What table are you referring to? I was taught the term "Gage" to be the centerline bolt spacing between two or more connections that are transverse (perpendicular) to the load direction. The can be different from how "jimstructures" defined it above, depending on how loads are applied (e.g. tension vs shear)

 

[WillisV]

@Qshake - true to a point, but the workable gage distance defined in the current AISC property tables really is just a guideline to make standardization easier and to give engineers/detailers a "go to" number where everything (clearances, edge distances, etc) is assured to work. It comes from an era when re-tooling machinery was much more difficult than it is these days, and newer machinery can also drill holes a good bit closer to the fillet (though you still have to watch out for bolt entering/tightening clearances). It is certainly possible, and I have many times, to use gage distances both farther apart and closer together than the workable gage value provided by AISC.

This is a very good article that walks through most of the main issues:

http://www.modernsteel.com/Uploads/Issues/May_2010/052010_May10_W_Shapes_web.pdf

 

[pplbb2011]

Appreciate everyone's contribution, WillisV's link is much useful for reference, thank you so much.

 

[Gumpmaster]

Great article WillisV. It lays out everything quite well.

 

[SAIL3]

WillisV is dead-on....found out just today that if your washer rides up on the "k" value..you use a "clipped" washer rather than a beveled washer which you would normally use on the fla of a channel

 

[ToadJones]

WillisV Is correct.
I have detailed many connections where I didn't use the gage. One column might have a 5.5" gage, and the next 3.5" but 4.5" might actually work for both and therefore standardize my beam end connection gage as well.
I know it made the fab shop happy.