Reinforcing Existing Joist Girder web members with intermediate connectors

[mmarlow]

Hello,

Im in the process of analyzing an existing Joist Girder for the loads of new RTU's. The Web members are double angles and are 20-30% over stressed. Which does seem strange because the chord members appear adequate.

These web members have no intermediate connectors. Is it reasonable to add intermediate connectors to get more capacity out of these web members? I cant think of a reason why not, but I cant find a situation where someone else has done this or recommended this on this forum. If I add the required amount of intermediate connectors from AISC table 4-8, I get plenty of capacity.

I will also address welds and reinforcing the girder seat. The chord members appear adequate (2% over stressed).

Also, I have modeled the girder per SJI recommendations of using a k=1 for all members.

Thank you for your help.

-MMARLOW EIT

 

[CANPRO]

I think your approach is reasonable. I've used the same method for strengthening both web members and double angle top chords. I'm assuming you did this already, but I'll mention that with the connectors you need to check the unbraced length of the web between the connectors, then the combined double angles for the total length of the web.

 

[mmarlow]

CANPRO,

Thank you

-MMARLOW EIT