Finding Tension and Shear Loads of Seismic Snubbers

[John Buchmann]

Hi,

When I want to calculate tension and shear loads of cables at picture below, I am using equations below;

Cable Load (Fc = Horizontal seismic force / cos60°)
Tension Load (T = Fc x sin60x1,3)
Shear Load (V = Fc * cos60x1,3)

However, I want to use seismic snubbers to mount my panelboard like picture below. How can I calculate tension and shear loads?

 

[e hilton]

In that example, wouldn’t the shear load for each snubber be 1/4 of the total shear force?

 

[John Buchmann]

In that example, wouldn’t the shear load for each snubber be 1/4 of the total shear force?

Correct, but I want to learn about tension stress. I think it would be 0 kgf.

 

[Mark K]

In detail 1 I would not call these brackets snubbers. Snubbers tend to be compression only items.

There will be non-zero tensile forces on some of the anchors under gravity as well as additional tensile forces due to seismic loads. The magnitude of the tensile forces will be dependent on the dimensions of the brackets. the dimensions of the cabinet, and the location of the mass within the cabinet.

Nothing is said about the material the anchors are connected to.

For the vertical cabinet I do not understand the dimensions of the cabinet and the slopes of the cables. At most only half of the cables are in tension at any one time. Consider the situation where the horizontal seismic forces are.
not acting parallel to one of the axis of the cabinet.

 

[jar546]

Many of these cabinets are unequally loaded as the gear is mounted to the back of the cabinet.