Return to index: [Subject] [Thread] [Date] [Author]

RE: AISC Eccentric Bolted Connection Tables

[Subject Prev][Subject Next][Thread Prev][Thread Next]
The requirements for shear tabs on page 4-52 come from tests at UC-Berkley.
The two provisions that you mention (for the plate yield strength and
thickness) are there to ensure that the beam end rotation assumed for simple
beam behavior can be realized. They allow for bolt "plowing" in the plate
material to accommodate such rotations. The weld size of 0.75 x plate
thickness is also derived assuming 36 ksi yield plate and equating weld
strength with the plate yield strength (allowing for plate yielding before
rupture of the welds). This design procedure is intended for transferring
beam shear, not beam axial loads. 

The IC method is another thing altogether. It is used to determine the bolt
group capacity used in the shear tab tables, but is not subject to the same
limitations of the shear tab design procedure. The 0.34 in. deformation
capacity used for the bolts does include bearing deformations of the plates.
I would assume that a large amount of this deformation does take place in
the connected material. So, for thick plates you may want to consider using
the elastic method instead. It may result in another bolt, but would save
the time of determining a delta max for your case.

Double angle connections may be another possibility. There is a design
procedure in Tamboli's "Handbook of Structural Steel Connection Design and
Details". I also believe that there is a Sept '95 ?? Steel Interchange in
Modern Steel where Thornton discussed the rotational ductility of Tee and
double angle connections subjected to shear and axial load. There is also a
section on rotational ductility of simple shear connections in the new 3rd
Ed LRFD Manual. This section does not exactly fit, but can be adapted to get
to Thornton's procedure.

HTH

-Heath  

-----Original Message-----
From: Markajohn(--nospam--at)cs.com [mailto:Markajohn(--nospam--at)cs.com] 
Sent: Wednesday, January 02, 2002 8:51 AM
To: seaint(--nospam--at)seaint.org
Subject: AISC Eccentric Bolted Connection Tables

I need some help interpreting what I read about eccentric connections with 
bolts in shear.  On page 4-52 of the 9th edition of the AISC Manual, there
is 
a discussion of the instantaneous center method based on shear plates having

an Fy of 36, having a thickness of no more than half the bolt diameter plus 
1/16" and that a bolt a bolt can sustain its ultimate load at a deformation 
of 0.34" (page 4-58).  According to Salmon and Johnson, the 0.34" includes
no 
slip.

Can a ¾" bolt really sustain its maximum capacity if you shear it 0.34"?  Or

is most of the deformation assumed to occur in the plates.  Am I reading
this 
right?

I am designing some connections for drag members which need to take a lot of

axial load and I need to use some thick plates and sustain some end
rotation. 
 I am bumping up against the design assumptions of the tables in the manual.

Thanks in advance
Mark Johnson

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ******** 

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********