Joist structural details vs. shop drawings 1

[conceng]

Often times engineers include the weld requirements for joist bearing that are not consistent with the shop drawings submitted by the joist supplier. Should one go with the more stringent of the two, or do the structural engineer approved shop drawings supersede the plan details?

Greg

 

[Bobber1]

I think this is an excellant discussion and I appreciate everyone's thoughts.

Here's an unusual one: I once worked for a large consultant on hydro projects and the company realized they were spending almost as much time reviewing all the shop drawings as they were putting into the design. On one contract, it was agreed with the owner that, instead of requiring and reviewing shop drawings, we would increase the level of detail in our design to make field inspection possible directly off the design drawings. The contractor prepared the shop drawings anyway since that was "industry standard". Differences were generally caught in the field. This concept worked faily well - "catching the differences in the field" caused some extra costs but generally our overall cost to the owner was less. This method was abandoned when company attorneys advised against it because it opened up the box of "not meeting the standard level of practice".

 

[efsinc]

You must be very careful here.
The Hyatt Regency skyway system was not underdesigned; unbuildable perhaps, but not underdesigned. The fabricator, through the shop drawing review process, suggested an alternative design which looked quite similar at a glance (to a non professional, or even a careless professional) but which effectively doubled the load on the nut and rod system. Whatever the review process in that engineer's office, the alternative got through, got built, and the rest is history.

Means and methods are the province of contractors. Members and connections are the province of engineers.

 

[JAE]

efsinc,
If you review the NDS report on the Hyatt - the original design was also slightly under-strength as the rods were bearing at a seam weld between flange tips (per NDS physical tests)

The splitting of the hangers just made it very worse.

 

[efsinc]

JAE thank you.
I learned in my practice from Kansas City to take shop drawings very seriously. Detailers are not engineers. Fabricators are not engineers. They are not licensed to insure public safety.

 

[conceng]

Wow gentlemen, I didn't think this was going to be such a can of worms when I opened it.

Our involvement in projects is QA/QC where we are inspecting the welded connections. Typically if there is a discrepancy due to insufficient thickness of base metal (3/16" weld required for 1/8" thick short-span joist bearing angles), we just note it on the inspection which typically makes it to the structural engineer.

For now we will continue with our status quo and base inspection deficiencies on the most restrictive between the plans and shop drawings. If the contractor thinks the engineer is asking too much, he can pursue a change.

In our market we have structural engineers who detail all the welds and those that just reference SJI or the shop drawings.

Thank you all for the very interesting discussion.

Greg