Joist to Steel Beam Lateral Conx.

[abusementpark]

I have a question about the connection of a steel joist to the top of a steal beam. When lateral load is being transferred from the diaphragm to the steel beam through the joist, there is 2.5" of eccentricity in the connection from the joist to the beam. (2.5" is the standard depth of the joist extension)

How do you typically account for this eccentricity? At my workplace, it is always neglected and I am wondering if this is an OK practice??

 

[JAE]

I believe common practice is to do one of three things:

1. If the load is fairly small, ignore it.

2. Specify on the drawings that the joist manufacturer must design the seats for X lbs. of lateral force at the seat.

3. Add 2 1/2" square steel tubes between the joists and use a continuous deck edge angle as a diaphragm collector to transfer the diaphragm shear into the tube and then into the beam. Tubes can be included in a set number of spaces as required to transfer the shear and limit the axial force build-up in the angles.

Of the three above - I usually use 1 or 3 as I believe the SJI isn't too keen on the 2nd option.

Other opinions?

 

[DaveAtkins]

I agree with JAE.

Fisher's book on designing with steel joists has allowable values for what you are describing, known as "joist seat rollover."

DaveAtkins

 

[jike]

JAE:

I usually use method 2 or 3 and have never had any problem with the joist manufacturers from option 2.

Dave: I specify the joist rollover loads and deflection so that the manufacturer can design the appropriate seat.

 

[abusementpark]

There appears to be some detailed equations here:

http://www.pdhonline.org/courses/s116/s116.htm