Weld Size Calculation for Plate Welded Perpendicularly to RHS Beam

[nevo2011]

Hello everyone,


I’m working on a welded connection between a rectangular hollow section (RHS) beam and a flat rectangular plate.
The RHS is fixed on one end, and on the other end, a flat plate is fillet-welded around its perimeter (full weld) to the open face of the RHS.


The flat plate is intended to be pulled downward, perpendicular to the beam’s axis – generating axial tension on the plate and corresponding load on the welds.


I’m looking for guidance on how to calculate the minimum weld throat size required in this configuration.

 

[kingnero]

Force / (2 x throat x effective weld length of one vertical weld) <= allowable yield.

Give or take some of the national parameters like allowances on material values, weldments, safety factors.

Don't count on the horizontal welds.

 

[duckhawk]

If you have a steel manual, equations are given in Chapter J section 4.

Like kingnero said, don't consider the horizontal welds, only consider vertical welds. This is a conservative approach.

First, required force for each weld needs to be calculated. This can be as simple as dividing Force by 2.

Then the allowable force for each weld needs to be calculated. From AISC 360 ChJ.4, if using LRFD, phi*Rn = 1.392*D*l, where D is the weld size in sixteenths of an inch and l is the length of the weld. This assumes FEXX = 70 ksi for weld strength.

Finally compare required and allowable forces and see if the weld passes. If it doesn't, the weld size D can be increased.

To fully check the weld, the base metal must also be considered. Here is a video that may help:

 

[Stress_Eng]

I don’t know how significant this is, but don’t forget that the beam bends, resulting in rotation at the free end. The rotation and the length of the plate will result in a horizontal offset between the point of load application and the N/A of the beam at the free end, causing a moment.