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Effective width for fasteners
10

Effective width for fasteners

Effective width for fasteners

(OP)
When using a high strength bolt clamping two pieces of metal together. What effective width do you use on each side of the bolt hole to determine the effective flexural width? Is there a value prescribed by code? or by common useage? I typically consider 4 x the thickness of the material on each side for a total of 8 x the thickness.

For a 1/4" thick plate, I would normally use an effective width of 2".

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

The way I was taught and have done it ever since is to consider a shear angle.
For example, if you have a 6" square HSS and a base plate with bolts at 9" each way, the distance from the center of the bolt to the HSS is approximately 1.5"xsqrt(2)=2.12". The approximation neglects the bend radius at the corner of the tube. If the shear angle is 45 degrees, then the effective width is (2)x(2.12)=4.14". Some might consider 45 degrees as unconservative. If the shear angle were 30 degrees, the effective width would be 2.45".

1/4" plate with HSB??

RE: Effective width for fasteners

(OP)
Thanks... the bolt is in a metal base plate securing a post, with gusset plates. The span is the distance between the gusset plates with the bolt located at mid span. I'm assuming the width of the section as 8x the thickness to determine the plastic section to develop the moment resistance of the base plate.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

(OP)
This is the condition.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

dik,
where is the applied moment?
and how are you getting flexure at the fastener line with the gusset plates there?

RE: Effective width for fasteners

(OP)
At the post and it is transferred to the bolt circle and anchor rods.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

ok, so with a moment on the post,
on one side the fastener is in tension, which pulls down on the base plate; more of a pull thru condition than overall bending of the base plate,
on the other side there is contact between the base plate and ground, so there is a distributed pressure on the bottom of the base plate,
the gussets stiffen the base plate, so the critical bending section probably is a line connecting the ends of two gussets, but there is not much pressure outboard of that line to bend the plate,
so doesn't seem like the base plate would fail in bending before a compression crippling failure of the gussets or tensile pull thru at a fastener.

RE: Effective width for fasteners

(OP)
The gussets can be designed to accommodate the bolt/moment forces. What I'm wondering is the effective width to use for calculating the moment resistance of the base plate.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

(OP)
Just checked DG 1, and can't find anything...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

3
Need BA’s yield line knowledge but with the gusset configuration this seems like an appropriate yield pattern:

RE: Effective width for fasteners

(OP)
Thanks Celt... I'd normally do a yield line solution; I was looking for a quick simple solution... just a span and a tributary width to calculate the Mp... The span seems simple enough and I usually use 8x thickness for a trib width. I was wondering if others had any other trib widths.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

the failure lines that Celt drew are only for the location where fastener is in tension. but I still doubt those locations are more critical than pull thru of the fastener thru the plate locally or failure of the fastener in tension.

RE: Effective width for fasteners

(OP)
The fasteners will not go into compression... Base plate and gussets look after that.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

2

Quote (I typically consider 4 x the thickness of the material on each side for a total of 8 x the thickness.)


IMO, 6t is more reasonable. I agree with Celt83 (Structural) solving with yield lines and a PBS for his post.
We are at the other side of ocean . The approach in Euro Zone at the attached doc.


According to the grace of God which is given
unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. . . .
I Corinthians 3:10

RE: Effective width for fasteners

(OP)
Thanks... it works with 6xt also... If I had lots of them to do, I'd use a yield line approach...

and a BPS for your's too...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

(OP)
dvd... I cannot open the file... thanks...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

I would use 4t in this case.

RE: Effective width for fasteners

I don't think there is a basis for any multiple of t as the width. Usually a 45 degree angle is used, as kind of a quick and dirty assumption that it will be more conservative than a proper yield line approach. If you were to crunch the actual yield lines you would see the thickness does not affect the controlling pattern.

RE: Effective width for fasteners

(OP)
A portion of the width will be effective... I was just wondering what others would use. I'm comfortable with 6xt for the total width, considering the bolt, nut and washer will contribute. It was just a 'meatball' approach that I often use for expediency.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

(OP)

Quote (1/4" plate with HSB??)


The thickness was just used for the example to determine the width. The actual plate is 5/8" thick.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

I would specify a nice, thick washer to increase my effective width and use 4t from the washer edge.

RE: Effective width for fasteners

The effective width is more a function of span and support conditions than it is plate thickness. A longer span mobilizes a much wider effective width. For a monolithic steel plate you will typically obtain an effective width similar to the span distance, which is reflected in Celt83's yield line drawing.

RE: Effective width for fasteners

(OP)
Thanks, Tom...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

(OP)
dvd... thanks...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

I would have answered this differently a couple of months ago, but I think this is the correct failure mode.

RE: Effective width for fasteners

(OP)
I suspect it would be close... thanks, BART. I'll see how it compares to what I used. Project is already done and out.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Effective width for fasteners

Good research thoughts here thumbsup2
thanks to you ALL
Also, sine you want to increase flanged diameter of base plate, why you don't apply double nuts technic ?


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