Bearing Plate Design

[dik]

A friend (also an engineer) has asked about the design of a bearing plate for supporting a glulam beam to a concrete wall/column.

The bearing plate can be considered as an L with the horizontal leg providing bearing and the vertical leg being anchored to the wall/column.

In the middle of the L, there is a vertical plate that is welded to both the horizontal leg and the vertical leg, effectively providing a stiffener in the middle of the glulam beam bearing.

Is there a simple manner of analysing this? without using a yield line or FEM approach. There are several dozen of these beam seats involved.

Thanks, Dik

 

[Lion06]

I'm imagining an angle with the vert leg point down and the stiffener as you not. Unless the angle is unusually long and very thin, I would just check it as cantilevering from the sitffener on both sides (neglecting the fixity to the vert leg).
Even for a 9.5" wide glulam, that would cause a beraing stress of 4.75" on each side of the sitiffener. Only a pretty high beraing stress with a thin angle will cause that to not work in bending.

 

[msquared48]

The stiffener that you are referring to is actually a called a "Kerf Plate". If I read you correctly, it will be sawcut into the glulam with one ortwo thru-bolts. This effectively divides the bearing plate into two cantilever bearing regions. Conservatively, I would ignore the extra stiffness of the back plate, and only deal with the kerf plate as stiffening the bearing plate.

I would design the bearing plate with a moment of wl**2/2, and an allowable bearing stress of .75 Fy or 27ksi. M is in kip-inches.

w is the load in psi from the beam reaction, and the bearing plate thickness "t" is calculated using the square root of 2M/27.

Mike McCann
MMC Engineering

 

[hokie66]

The bearing stress for the glulam and the required end distance for connectors should determine the size of the horizontal plate.

The stiffener should be sized to support the vertical load, and its weld to the vertical plate should develop the reaction.

The vertical plate size will depend on the connections to the wall or column.

Same as a stiffened seated beam connection with a steel beam. AISC details should help.

 

[dik]

Thanks, gentlemen...

Dik