Col Splice

[SAIL3]

Attached is a col splice I designed and have nagging concerns about. It is a hopper platform of approx 11' by 16' with moment frames in each direction. Indoors, ASCE7-05, seismic cat "B", seismic shear is 0.05W, overstrenth factor of 3.0, Cd=3.0, used R=3.0. On the frame shown in the attachment the seismic load was 0.7kips applied at the top. Design mom @ splice 6.0 ft-kips, deflection approx 1". With overstrength factor the moment is 16.3 ft-kips. I did an approximate design on the splice plates. It is already erected...initially, the plan was to remove the 3/4"dia bolts and plug the holes...I may have them leave the bolts installed. It in the food industry and the requirement was no bolted connections. Any comments on the design are welcome...thanks

 

[SAIL3]

forgot to mention that these are ASD loads and appoligise for the upside-dn page in the attachment..

 

[gtaw]

Review the requirements for skewed T-joints in AWS D1.1. The skewed T-joints have some requirements regarding sizing of the weld that appears to have been overlooked.



Best regards - Al

 

[SAIL3]

gtaw....you are probably correct on that detail "E"...in this case the members are lightly loaded and typically in my design I do not count the weld accross the face of HSS members unless I have to...the majority of the load is reacted in the side face when all members are the same width due to relative stiffeness...
Additional info on the col splice...I used an effective width of the 1" splice plates of 9" as a conservative approximation method of calculating the moment capacity of the plates..attached is a shot of the erected structure...

 

[BAretired]

Looks like Detail E was not followed by the fabricator, probably due to the difficulty of welding at the corner of the 8x4HSS. The structure looks okay to me. I agree with leaving the bolts in place as it stiffens the 1" thick plates.

BA

 

[paddingtongreen]

The food industry doesn't like bolts, dust can be trapped and little creatures can hide behind them.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[SAIL3]

thanks BA for the response...on detail "E"..it was for the lightly loaded col lines...another detail which was not shown in the attachment was used for main gravity-loaded frames...

 

[IFRs]

Could you have used a smaller plate on top and welded the plates together in the field, then removed the bolts?

 

[BAretired]

IFRs, that is precisely what he did do (see Detail "F"). The top plate is 1'-4" and the lower plate is 1'-6". Removing the bolts may be okay, but the plates are more flexible with bolts removed so, from a structural standpoint, it is better to leave them in place. If the client does not want bolts for hygienic reasons, they may have to be removed.

BA

 

[IFRs]

Oops - did not look at it all. And there I thought I was being brilliant! The plates could have been stiffened with gusset plates if needed, which could have been designed into the system. Too late. Perhaps take out the bolts, put in solid rod that can be plug or fillet welded to close the holes and stiffen the plates? Maybe re-examine the plates and allow plastic deformation as long as failure does not occur? I've done similar projects for the food industry - they are very picky about cracks and crevasses.

 

[TXStructural]

When I've planned splices on HSS columns for field welding, I always have the welds top and bottom of the same plate to avoid such issues. It introduces others, but avoids loss of stiffness with the oversized plates. I suppose the (expensive but easy) alternative is to cut down the perimeter of the plates and reweld. IFRs' idea would seem an appropriate solution if you don't need clamping forces.
It does look like there are some hard-to-clean areas at the gussets and other connections.