How bad could a beam shear induced eccentricity be on columns 5

[IJR]

In the last couple of weeks, connection of 2 floor beams with common bolts to a column web has undergone serious criticism, and the connection is reportedly prohibited in OSHA specifications.

Before this discussion I was told that the connection was preffered because it doesnt add eccentricity to column.
A friend, taking into account both discussions, has decided to eliminate use of this connection. Instead, we are planning to add short brackets from web of column and then attach the beam to this bracket with end-plate bolted connection.

Now here comes some eccentricity.

My concern is : 1) Is this eccentricity worth taking into account?
2) I would like to go back to my older connection, simply because it is easy to fabricate and I believe I can provide additional bolts("safety bolts&quot for easier erection.

Respects

IJR

 

[JAE]

I would think you could still use your same connection, just provide an erection seat for one of the beams to meet OSHA.

 

[IJR]

Thanks JAE for the immediate response and supporting the concept which I favor.

If you visit here again please let me know how you feel about eccentricity of connection shear with respect to column design and analysis. I usually tend to ignore that. Actually Thornton (One old AISC great guys mentioned that somewhere in one of his articles on connection design)

Respects JAE
IJR

 

[dik]

I'm not aware of OSHA requirements.

Does a bar welded across the toe of the flanges provide adequate temporary bearing support? For safety reasons, the steel member should be slung as thought the bar were not in place.

As far as seated connections, I usually (for anything but light loads) do a quick shear and moment check on the connector to ensure that there is sufficient strength to transfer the reaction to the C/L of the column with a moment equal to the reaction * the offset and assume that the load is on column C/L. Also use thicker connection plates to accommodate prying loads.

I had about a dozen or so of these connections last week and decided to do a little 'knock-off" program to check the bolt shear and tension values... have to find the time to sit down and write it...

 

[Taro]

JAE is right. Using an erection seat or adding a couple bolts should work fine.

IJR, Don't neglect the moment due to eccentricity in the beam connections, especially if the loads are unbalanced. It doesn't take much eccentricity about column's weak axis to make a highly loaded column fail the interaction equation. Also, note that the OSHA rules now require 4 anchor rods at the base conneciton and also specify a minimum load and eccentricity that column bases must be designed to withstand during erection.

 

[Ron]

IJR...Agree with JAE and TARO...use the seat and check the weak axis interaction.

OSHA only applies for a short time. The connection sees the loads forever (hopefully!!)

 

[dik]

Taro
What are the OSHA load and moment requirements for AB design? Is this for all installations and are there any exemptions?

 

[Taro]

dik,

"Columns, column base plates and their foundations must be designed to resist a minimum eccentric gravity load of 300 lbs. located 18 in. from the extreme outer face of the column in each direction at the top of the column shaft"

for more information, see the AISC advisory on OSHA rules at:

http://www.aisc.org/documents.asp?mode=docdetail&doc=246

 

[dik]

Taro:
Thanks have downloaded the pdf and printed it...

 

[JAE]

I believe OSHA is now requiring ALL columns to have 4 anchor bolts, not allowing 2 bolts per column, due to stability requirements. We have a steel erector coming to give us a quick lunch seminar in a couple of weeks. He is actually one of us...an engineer, who just jumped over to handle steel erection. I'll post anything new that he offers.

 

[IJR]

JAE

It is really nice to see all great guys in this forum. I used to shy away from posting questions here simply because there seemed to be less visitors.

How shall we be informed of the post that you will make after the seminar. I am highly interested.

If you also know of AISC related sites that post such pubs on regular basis, please suggest.

Respects
IJR

 

[dik]

I notice in the AISC Advisory regarding columns "that splices must be designed to meet the same load-resisting characteristics as columns." Does this mean that splices must be capable of developing the full moment capacity, too?

 

[JAE]

Just noted that there is an excellent article in the latest "Modern Steel Construction" Magazine regarding new OSHA standards that affects steel construction.