Threaded Rod Welded To Plate Material

[BadgerPE]

I am working on checking the capacity of a provided detail for a silo base attachment. In the provided detail, 1" dia. bent rod was welded to a plate and this was then cast into the concrete. The silo would then be welded directly to the plate. I have substituted heavy hex bolts instead of the bent bar. However, I have been unable to determine how to calculate the capacity of the anchor rod/weld connection. Any thoughts or comments on where to find guidelines relating to a connection like this? Please see attached existing detail.

 

[dhengr]

Crackerjack47:
Draw the welded detail full size, the bottom of the plate, the bolt and the two sections of fillet weld, a cross section through the center of the bolt. Draw in the two fillet weld throats, find the center of the throat length on both throats, and measure btwn. them. This is (bolt dia.) + (.707 * fillet leg size) and defines the weld dia., which then defines the circumference of the weld. This times the throat dimension, times the allowable weld stress for the welding rod being used, is the capacity. You might want to use a slightly smaller circumference to be conservative, and use two bolts per plate.

 

[charliealphabravo]

If you are a checker is it really your job to generate the capacity calculations? Couldn't you ask for calculations to be provided? Especially for an irregular anchor rod material and geometry. Does the plan specify the radius of the bend or the length of the hook or the material spec? Is the weld specified?
As a checker you might alternatively consider rejecting the drawing and request that a more conventional material and anchor be provided like a heavy hex head anchor rod welded to the bottom of the plate. There are lots of tools to easily check this configuration.

 

[BadgerPE]

DH--Thanks for the info. I wasn't sure it was as straight forward as that, so its good to hear another think so!

CAB--I should have been a little more clear defining what I am doing. The detail was provided to us by a contractor who would like to install a silo using this detail from a previous project. I am responsible for this project and I am running the calculations on the connection for this particular silo application. Therefore, I am not simply checking someone else's design as I erroneously stated originally but rather designing the connection to loosely follow the detail provided.

 

[KootK]

The PCI handbook has some tabulated values for rebar welded to plates. It might be instructive to check that out for comparison.

 

[ToadJones]

Can you weld heavy hex bolts?

 

[ToadJones]

Could you possibly use threaded rods (threaded both ends) use nuts and washers to connect the plate to the rod....could be an interference issue...
Another nut with or w/o an anchor plate can be cast into the concrete.
Heavy hex nut develops the full strength of most rod material.

 

[dcarr82775]

I have been this detail many times, always from steel tank manufacturer's. Assuming the materials are all compatible, Dh says how to calc the weld strength, so just find the controlling limit state. I don't think that weld will develop the full strength of the steel bolt, but maybe it doesn't have to.