Eccentrically loaded bearing plates

[PG35]

In a job I'm involved in, the contractor did not install the joists centred on the bearing plates. I guess the mason was not careful enough to locate them properly. Anyways, I was give the task to review the condition.

I believe that the pressure below the entire plate area will not be uniform. How do I determine the pressure distribution below the plate? I would also need this info. to review that adequacy of the plate thickness.

I'm sure this is a common occurance, can anyone help me out?

Thanks,
PG

 

[Lion06]

treat it as a base plate with the P from the reaction and M=P*e

 

[nutte]

I would check the plate for bearing/bending using only the concentric portion of the plate.

 

[DaveAtkins]

The bearing plate will have a trapezoidal or triangular pressure underneath.

DaveAtkins

 

[msquared48]

1. Check to see what the maximum bearing stress to the plate is using P/A + M/S.

2. Then, knowing the thickness of the plate, see what the maximum distance is that thickness can cantilever to using wl^2/8 for the moment and an allowable 27ksi bearing stress, assuming A36 material.

3. If the maximum is less than the actual, you're OK. If not, you may consider adding some vertical triangular stiffeners from the column to the area of greatest cantilever of the plate, reducing the maximum moment seen by the plate.

4. Recheck it with the stiffener plate.

Mike McCann
MMC Engineering

 

[spats]

Your design is so close that having the load off-center is a problem? In the real world you'll almost never be centered. If the portion of the plate that is centered on the joist works, no worries.