Beam to Column Connection Identification
Beam to Column Connection Identification
(OP)
All,
I have a steel structure (built approx. 1974 to 1978) with some column deterioration at a girder connection. The girder to column connection is a bolted extended end-plate connection which is welded to the web of the girder. At first glance it appears this is a moment connection, however the flanges of the girder are not welded to the end-plate. In fact, the top flange is not even in contact with the end plate. I've attached a photo of the connection (in good condition). Note, we do not have any documentation of the original construction, however it is known that the beam seat and stiffener plate were not part of the original construction and added by another engineer about 10 years ago.
I would like to know if anyone has seen a similar connection and if they can give some quidence into its original design. I have done some research, but cannot confirm if it is intended to be a partial-strength connection to reduce the simple span moment on the beam or if it was originally designed to be a shear connection. Any one have some insight into this?
I have a steel structure (built approx. 1974 to 1978) with some column deterioration at a girder connection. The girder to column connection is a bolted extended end-plate connection which is welded to the web of the girder. At first glance it appears this is a moment connection, however the flanges of the girder are not welded to the end-plate. In fact, the top flange is not even in contact with the end plate. I've attached a photo of the connection (in good condition). Note, we do not have any documentation of the original construction, however it is known that the beam seat and stiffener plate were not part of the original construction and added by another engineer about 10 years ago.
I would like to know if anyone has seen a similar connection and if they can give some quidence into its original design. I have done some research, but cannot confirm if it is intended to be a partial-strength connection to reduce the simple span moment on the beam or if it was originally designed to be a shear connection. Any one have some insight into this?






RE: Beam to Column Connection Identification
RE: Beam to Column Connection Identification
A couple things lead me to believe that:
1.) The bolts are grouped high and low. Typically, shear connections only are not grouped this way.
2.) There is a stiffener across the column web at the elevation of the girder bottom flange.
3.) Original or not, the bottom flange seat appears to be welded to the bottom flange, thus
adding to the rotational restraint of the girder end.
How much rigidity was originally there?....hard to say. With the flanges not originally welded, it would be more rigid than many typical shear connections...but less rigid than welding up the flanges to the face of column. Also, like I say, coming back 10 years ago and welding up the stiffened plate to the bottom flange made the end connection even more stiff.
In analysis, you may have to look at it twice. Once, assuming a more flexible end condition, resulting in more moment out in the girder span.....and again assuming a more rigid end connection, resulting in more moment in the column, girder end, and girder across the column web.
RE: Beam to Column Connection Identification
The alternative to this is to get proper rotational fixity stiffness data for the connection. I must say that the connection is not altogether unknown to me but I don't remember where I have seen it (apart from when for simply supported cases) and an inspection looking for the case in what I have may take some time.
Maybe the rotational stiffness of the connection, since bearing on a quite rigid front end plate and restricted by the flanges can be initially extrapolated from that the double tee semirigid connection and then factor by the quotient of inertia of the web divided by inertia of the whole double tee. Data for the semirigid connection double tee in the Chen and Goto text (even if I doubt applicable to front plates restricted to the height of the double tee, but it is a start). Probably the approximate estimate as per above should render even less rotational stiffness than actual, because the front plate and flanges must be influencing the stiffness more than proportionally as assumed.
A third approach and also reasonable in effort for such single question is to make a 3D solid FEM model. This will get quite well the behavior.
RE: Beam to Column Connection Identification
If you need to rely on negative moment, it might be prudent to develop the top flange as well. If the beam works as a simple span, leave it alone.
BA
RE: Beam to Column Connection Identification
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Beam to Column Connection Identification
RE: Beam to Column Connection Identification