Partial Beam Reinforcement
Partial Beam Reinforcement
(OP)
I will be partially reinforcing a beam with a WT. I am looking for guidance as to determining the length of WT to provide. I've calculated moment diagrams and know the length exceeding the moment capacity.
My question concerns the require length of WT beyond these points. How do you detrmine this length and are there code references for this?
Also, the WT would be stitch welded, but typically there is a continuous length at each end ("tail weld?"). How and where can I find information on determining this weld length?
My question concerns the require length of WT beyond these points. How do you detrmine this length and are there code references for this?
Also, the WT would be stitch welded, but typically there is a continuous length at each end ("tail weld?"). How and where can I find information on determining this weld length?
Richard Beard, PE
Century Engineering, Inc
www.centuryeng.com






RE: Partial Beam Reinforcement
I would extend the WT past the theoretical cut-off point at least enough to place the end weld and then more so you can have some tolerance if they place the WT in the field off from where you specify.
RE: Partial Beam Reinforcement
WillisV's response discusses the cover plates which are thin. Thus the design is based on the weld length to fully stress the plate.
The WT will have a much greater variation in stress levels. This would mean the WT flange would reach full stress prior to the web where the attachment is made.
How does this affect these calculations? I would assume it would be conservative to assume the force in the WT to be fs*(Area wt).
Richard Beard, PE
Century Engineering, Inc
www.centuryeng.com
RE: Partial Beam Reinforcement
With this formula, you will account for the stress distirbution that you have mentioned in your post.
RE: Partial Beam Reinforcement
I'll give it a shot for the equation. Steel stress is a function of the distance from the neutral axis. Let's call that "y". We know we can use fs=My/I for the stress ionthe steel at a given distance "y" from the neutral axis. The variable "c" will represent the maximum value of "y", so the maximum stress would be fs max=Mc/I. The stress at the top of the bottom flange of the WT would be fs2=M(c-tf)/I and the stress at the top of the stem of the WT would be fs1=M(c-d)/I where tf is the WT flange thickness and d is the depth of the WT. If we take stress times the area over which it acts we can find force. The differences in stress at each location result in a trapezoidal stress distribution. The area of a trapezoid is the average of the two heights times the base. The force in the WT then becomes FWT=[(fs1+fs2)/2](d-tf)tw+[(fs2+fs max)/2]bftf. This is the average stress in the stem times the stem area plus the average stress in the flange times the flange area. The variables bf and tw are the flange width and the stem thickness, respectively.
Make any sense?
RE: Partial Beam Reinforcement
RE: Partial Beam Reinforcement
Richard Beard, PE
Century Engineering, Inc
www.centuryeng.com