Advice for strengthening a steel beam web for shear? 3

[williamsg]

I have a steel I-beam whose shear capacity is not enough.
I can only think of making a “sandwich” web by welding two plate each side. Any good advice?

 

[DWHA]

Is the beam coped? This is a rare occurance that the member fails in shear prior to flexure. Is it a must that you use this beam?
From my experience, other than adding plates along the web, there is not really much that you can do.

 

[kelowna]

Not my forte, but depending on the geometry of the beam the shear capacity gets reduced based on web buckling, in which case adding longitudinal or transverse stiffeners increases the shear capacity. Is this your case?

I worked on a project before in which webs were strengthen by welding threaded rods (in a similar way to the way shear connectors are welded) and bolting a plate to the web. It worked, but it was very time consuming

 

[JedClampett]

As DWHA said, this would be very unusual. You'd need a very short beam with a very big load or a beam with a load near the supporting end. That being said, if your beam is having a shear problem, the end connection is probably having a more serious shear problem. So whatever you do to increase the beam's shear capacity has to be tied into the connection and the connection needs to have enough capacity,
It's also unusual for any beam connection to develop the full shear capacity of the beam.

 

[williamsg]

The W shape beam was used as a floor beam. Some longitudinal beam loaded concentrated force on it. Because there are pins and some supports underneath of the floor beam, so the flexure capacity is enough except shear capacity.

Could you give more comments? Thanks!

 

[DWHA]

Shear strength is dependent on the strenght of the steel and the area subject to the shear force (d*tw for W shapes). With that said there is only one thing that you can change, that is the area subject to shear. Adding plates to the web would be the answer. Be sure that welds are adequate to transfer force to the plates.

 

[jike]

A typical way to reinforce a member for shear is with a web doubler plate (adding a second web plate) as DWHA said. Make sure that it is detailed properly so that the load is shared between the web and the doubler plate.

As JedClampett pointed out, pay additional attention to the connection support detail, its capacity and how the load gets into it. Don't stop the web doubler short of the connection!