Welded Connections to Concrete Frame 1

Dear,

It does not seem that the steel elements are part of the seismic system (in this case you should see in FEMA how a well made welding is done ...)

I think they changed the type of connection. If I understand the drawing, the bolted connection is a shear connection ... the weld connection seems a moment connection.

Daniel

DomDunk

The thing is that the design has not been changed..the contractor did it because it was 'easier'. All the bolted connections are as on the drawing but they do not have the bolts in them,the plate is simply welded to the beam.

1) I wouldn't lose much sleep over this so long as:

a) everything is inside of the building envelope so no large thermal movements and;
b) the columns are designed to absorb weight coming in from the concrete frame where the attachment is rigid.

2) Sure, it's common, often unauthorized, field fix. The consequence would primarily be that you loose rotational ductility in the joint. Not ideal but probably acceptable.

I do not like that they weld in situ. Actually I do not know what revision procedure is required to control that the welds are well applied.

Regarding structural behavior, it should not change much. But you should check the weld connections resistance.

I repeat, because it is not about the seismic system or main elements (is it correct?), the thing is not so critical.

Thank you guys!!

The columns are not load bearing. I also ,really do not like the fact that they weld everything as in some cases I get a bit 'worried' that it changes the intended concept from pinned to fixed in a structure.

What about purlins welded to cleats? In this project, bolt opening in some purlins do not align with opening in cleats, so the contractor obviously weld them together. I red somewhere that welding of one component to another is not allowed when the component is subjected to repetitive, sudden and momentary forces. In my opinion forces acting from wind on a purlin welded to a cleat would fit the bill. Also the environment is highly corrosive so not sure if welding is right. What do you think?

Its not surprising the contractor had to weld all of the connections; that is a poor choice of connection type for a beam supported by concrete on both ends. A typical bolt hole is 1/16" (2mm) oversized...so the concrete and the embedded plates must be installed within that tolerance for the beam to fit...and that is an extremely tight tolerance to meet with concrete. There should have been long slots in the shear tab, with an allowance for welded the tab due to fit up issues.

Regarding the fix vs pin issue - a welded shear tab is an acceptable method of providing a shear connection, I see no issue with this. The issue I see, is originally the load from the beam was delivered to the shear tab between the bolts, but depending on how the tab was welded to the beam, you may have increased the eccentricity in the connection. Welding the top and bottom of that shear tab might have been difficult depending on flange width of the beam.

Bubik,

I dont see how the columns can be non load-bearing given the rigid connection to floor plates.
I'd be concerned about these columns if their design doesnt include any axial load.

You will get some prying on the embedded plates. How are they anchored in the concrete?

patswfc
Yes, absolutely...but why? The building is part of cement plant by the way. The building is concrete frame mill feed supporting massive bins(for additives and clinker storage) and more steel structure coming on top, all this had been built before those steel columns under consideration were added.


CANPRO
What I gather is that although a connection plate is welded to the beam and embedded plate it still can be pinned?



hokie66
here are the embedded plates