Cast in Angle Bending Question 5

[MindofBarca]

Hello All,

I have an insulated precast wall panel with a cast-in-angle with studs to provide support for roof joists (see attached detail). The angle is 6x6x1/2 and is subjected to 11.6k of ultimate shear force. I am trying to determine the bending/thickness of the cont. angle. The joist load is occurring roughly every 6', however, the angle and studs are continuous. How would I go about this calculation?

Is my b = 12" (distance of stud spacing?)

Right now I am doing a rudimentary thickness calc such as: t req = sqrt((m*4)/(phi * fy * b)) and coming up with 0.6inch ie 5/8" thick angle. Is this correct?

Thanks in advance, cheers!

 

[dik]

Thanks... didn't check... just noticed they should be there... I'll run it through my SMath when I get a chance... to check the numbers.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[BAretired]

I generally apply the load at the mid point or at the 1/3 point towards the rear... as the support deflects the point of load application moves closer to the back of the angle.

I might tend to be a little more conservative with that assumption and choose dimension 'c' to be about 2d/3, allowing for slope in the joist as well as the possibility that the joist shoe may not extend to the face of precast.

BA

 

[dik]

Thanks for the caution... if the joist is short then that is accommodated... still take the reaction near the joist end... that's where the load is applied IMHO.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[BAretired]

@dik
I'm not sure that joists are typically designed to take the reaction near the end of the shoe. Some may be, but that is one of the things that got Anthes into trouble.

BA

 

[dik]

Yes, but that's where the load comes into the angle... and as memory serves, Anthes remedied the loading... design based on mid shoe depth length but able to be supported at the ends. the shoe is much stiffer than the angle.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

Works...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[JLNJ]

It seems to me that the worst case is when the joist lines up with one set of studs.

It seems to me that all the tensile force goes into one top stud and the effective width of the outstanding angle is far less than the width resulting from the yield line method. There are some complex stress risers around that top stud.

 

[BAretired]

It seems to me that the worst case is when the joist lines up with one set of studs.

It seems to me that all the tensile force goes into one top stud and the effective width of the outstanding angle is far less than the width resulting from the yield line method. There are some complex stress risers around that top stud.

A 12" spacing of studs seems wasteful. It might be better if they were spaced at 3'-0" o/c (1/2 the joist spacing) and located either side of each joist location. That way, each stud pair would be responsible for only half the joist reaction. In case of misalignment, it may be prudent to size each top stud to take the full tensile force.

BA

 

[Brad805]

HCA are cheap and easy to install. I doubt they would want to complete detailed stud layouts for each angle, so I would design 2-HCA for the reaction. I doubt it will be much of a struggle for those reactions provided the joist is far enough away from a joint not near an opening. The trick will be the cases where you have a joist right at the panel joint or an opening directly below. The detail in general is not overly cost effective and is about simplicity. Precast Co's like simple and repetitive. We have put thousands of joists in pockets, and we would never entertain this concept.