Strengthening Open-Web Steel Joists 1

[RFreund]

In the article “Strengthening Open-Web Steel Joists” in the 4th Quarter, 2005, Engineering Journal the author suggests 3 items on page 1 of the article. The 2nd Item states to include top chord moments in the design even when panel points are less than 24”. However in the example it does not appear that the top chord is checked for combined axial compression and bending. In researching this topic further, combined bending/compression checks were not made in vulcraft’s “Special Topics – Joint Reinforcement” nor was it addressed in the presentation slides for the “Evaluation and Modification of Open-Web Steel Joists and Joists Girders” presented by SJI at the 2007 Structures Congress (I was not there so it may have been addresses).

So my question is:
1. Should a combined bending and compression check be made?
2. I know that if it is the design will be more conservative however is it typically done?

I posed the question to AISC so I'm sure I'll get a response from them however I was wonder how others have approached this.

Thanks,


EIT

 

[RFreund]

One other question would you model the joist as pin-pin or pin-roller?

Sorry I know I'm probably exceeding my question limit...but its January there's nothing else to do right?...

EIT

 

[ash060]

Yes you should check the combined bending and axial. The easiest way would be to check your top chord as a continuous beam with the panel points as supports. Yes it is typically done because it is required by SJI's specification.

Treat it as a pin-roller as this is the way it is done per SJI.

 

[RFreund]

Thanks, I thought so.

EIT