Beam seat angle
Beam seat angle
(OP)
This is a general question(s), not specifically related to any project.
1. In a typical beam seat connection, with a steel beam framing into a column using a single angle (although frowned upon) at the bottom of the beam bolted to the column. The bolts from the angle to the column are designed for shear and bearing, no requirement for tension from the eccentricity of the beam load on the angle to the column, correct?
2. In the same type of connection but loaded in a tension type scenario, i.e.: drag strut, e.t.c., the tension on the bolts is considered along with the prying action if applicable?
3. Combo the two above situations. If #1 and #2 are true i.e: there is both a beam reaction and tension force on this connection, they would be calculated separately. #1 would have no effect on #2 and vice-versa with the exception of the tension/shear interaction of the bolts. The tension in the bolts would only come from the direct tension of the drag load and prying, not from the eccentricity of the beam reaction, right?
This seemed relatively clear when I was typing it, but if not let me know!
Also, any references or design examples/problems are welcome.
1. In a typical beam seat connection, with a steel beam framing into a column using a single angle (although frowned upon) at the bottom of the beam bolted to the column. The bolts from the angle to the column are designed for shear and bearing, no requirement for tension from the eccentricity of the beam load on the angle to the column, correct?
2. In the same type of connection but loaded in a tension type scenario, i.e.: drag strut, e.t.c., the tension on the bolts is considered along with the prying action if applicable?
3. Combo the two above situations. If #1 and #2 are true i.e: there is both a beam reaction and tension force on this connection, they would be calculated separately. #1 would have no effect on #2 and vice-versa with the exception of the tension/shear interaction of the bolts. The tension in the bolts would only come from the direct tension of the drag load and prying, not from the eccentricity of the beam reaction, right?
This seemed relatively clear when I was typing it, but if not let me know!
Also, any references or design examples/problems are welcome.






RE: Beam seat angle
RE: Beam seat angle
RE: Beam seat angle
RE: Beam seat angle
In answer to No. 1, yes it is a typical assumption, and one that the AISC manual tables are built from, that the bolts are designed for pure shear loads (no eccentricity). This is based on the thought that the angle is flexible enough to provide beam end rotation and the outstanding leg itself is designed for the required bending moment.
I would be hesitant to use this type of connection with a large tension load however due to numerous factors including the large shear lag effect on the beam. If you were determined to do so note that tension stresses would combine with flexural stresses in the angle legs and the design should be performed accordingly.
RE: Beam seat angle
RE: Beam seat angle
RE: Beam seat angle
I think you are correct that for angles bolted to the columns, the eccentricity of the load on the angle-to-column bolts is ignored.
But for welded seats, the eccentricity is included.
This is stated in the 1986 AISC Journal article by Garrett & Brockenbrough, 2nd Qtr. which forms the basis of the seat connection tables in the AISC Manual.
RE: Beam seat angle
For your #1 condition, particularly if the bolts are pre-tensioned, you can consider that all bending occurs in the angle through the bolt line, thus the resulting tension in the bolts is nil and shear prevails.
While it is actually a bit more complicated than the simplified approach model (one significant factor is the relative stiffness of the angle), the error is not large when considering the simplified approach, thus making it much more useful.
RE: Beam seat angle
RE: Beam seat angle
RE: Beam seat angle
Nice Tip. Also in the 3rd Qtr of 1997 another AISC Journal was published by Yang and others. Thanks.
RE: Beam seat angle
I believe for Slip Critical Bolted Connections you can ignore the shear-tension effects but for bearing bolted type connections you can not. This is also the AISC basis for the end plate type connections. The theory is based on the shear friction developed between the two faying surfaces. Generally if your looking to totally prevent slip in your connection you will need more bolts than in a bearing type connection with the same load.