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Post - Plate - Concrete Connection Design - Moment Arm

Post - Plate - Concrete Connection Design - Moment Arm

Post - Plate - Concrete Connection Design - Moment Arm

(OP)
Hello everyone,

For the past couple of days I have been looking for the answer what is the moment arm length when designing each member of above referenced connection. Attached to this post is my sketch of the rail post connection to the concrete slab. Can you tell me the moment arms (Plate, bolt and weld design) in this particular example? I read this forum and a couple of articles but I can't find one straight answer to this issue.

Thank you in advance for your help.

Buleeek

RE: Post - Plate - Concrete Connection Design - Moment Arm

Assuming I am reading your sketch correctly, I'd use 42.375" to figure the moment for all of them except for the weld. (I'd use 42" there.)

RE: Post - Plate - Concrete Connection Design - Moment Arm

(OP)
Yes, that is correct, however, I think I did not express myself correctly. I'm asking about an arm of the tension force (from the bolts).

RE: Post - Plate - Concrete Connection Design - Moment Arm

(OP)
I don't want to start a new topic so I will just ask here.
1. Is it possible to weld an aluminum post to a steel plate?
2. An aluminum plate (5x5x3/8) seems way to small to carry a 200# load on 42in arm. The material 6061 T-6 has Fyw = 20ksi (the plate bends close to the welded connection). If I apply the ASD factor = 1.65 (aluminum) to the equation, I will get 12.121 ksi resistance. There is no way to use 3/8" aluminum plate of this size. 1/2" thickness is also way too small.

Any advice?
Thanks in advance.

RE: Post - Plate - Concrete Connection Design - Moment Arm

Typically aluminum cannot be in direct contact with steel. Galvanic action can occur.

RE: Post - Plate - Concrete Connection Design - Moment Arm

(OP)
That's what I thought. I'm trying to go figure out something else. Do I have to use Fyw vaule instead of Fy ? The plate will be welded to the post.

RE: Post - Plate - Concrete Connection Design - Moment Arm

Buleeek:
No doubt about it, you pay through the nose when you weld most aluminum at max. stress locations, becuase the welding heat destroys the tempering (heat treatment). When you have a bunch of these posts, it may pay to buy basic, untreated materials, do your welding and manufacturing, and then have them heat treated as completed units. The tempering is what gives them their much higher yield stress and ultimate strength, thus the (20ksi)/1.65 = 12.1ksi. You could design a bolted post/base pl. detail of some sort. You could lap the face of the slab edge with 50-54" long post and through bolt it to the conc. face. You would insert the 42" - 2x2, as a conatilever, in a cast in place 3x3 and then fill the remaining void with some pourable epoxy, or grout, or some such.

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