CJP in a Moment Frame

[MarkAJohn]

List,

I have an application where I wanted to weld a 50ksi wide flange (W8x40) to the face of a 1.25” thick 36 ksi plate and fully develop the 50 ksi wide flange. (it’s part of an ordinary moment frame and will be used in earthquake country) My client wants to do it with a CJP. I want to be able to show my client that he should add a fillet to the CJP and change the plate to 50ksi material, or else the 50 ksi beam won't be fully developed and, more importantly, that the weak link will be the interface between the weld and the 36ksi plate. This would produce a sudden brittle failure, not a good thing in earthquake country.

What I need is the following:
(1) opinions on whether or not a CJP will fully develop the 50ksi beam.
(2) opinions on whether or not changing the plate to 50ksi material and using a CJP plus a 5/16 fillet to allow the CJP to be back gouged would work.

TIA
MJ

 

[abusementpark]

A sketch would help.

 

[MarkAJohn]

This is an end-plate connection like the one shown in Fig. 12-6 (a) on page 12-8 of the AISC Steel Manual 13th ed.

MJ

 

[paddingtongreen]

Clearly, the plate fails before the W is fully loaded, and yes, a fillet weld will help.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Teguci]

1. A CJP would fully develop the 50 ksi beam. I would anticpate the need to backgouge or backer bar for a CJP weld. Rat holes in the top and bottom of the web should be cut to allow for CJP.
2. 36ksi plate would fail first due to the 70 ksi weldment to 36 ksi base metal transition. Per table J2.5, "Strength of the joint is controlled by the base metal." The weaker base metal would control. To adjust for this, the area of contact between the 36 ksi plate and weld may be increased with a fillet. A 5/16 fillet would account for up to a 3/4" flange. Not sure what you mean by allowing back gouging with the fillet. Either the reinforced CJP or changing the plate to 50 ksi. Don't think both are required.

Would suggest using detail b from figure 12-5 to get the plastic hinge away from the connection zone.

 

[Galambos]

i would suggest looking at the AISC design guide for end plate connections. i believe it notes that A.) rat holes should not be provided, and B.) end plate connections should not be used in structures with R>3.

i could be wrong, though!

 

[SteelPE]

Galambos,

I do not have the AISC Design Guide you are talking about however AISC 358-05 (Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications) does include bolted end-plate moment connections as part of their prequalified connections. This would mean that end plate connections can be used with R>3 as long as you follow their detailing requirements.

 

[MarkAJohn]

Thanks Very Much Guys,

I think I have what I need to state my case (that just a CJP to A36 plate won't work).

This is a valuable forum!
Mark Johnson PE