Seismic Weight of Walls 1

[frv]

I'm running in to a bit of an issue as I prepare for the SE exam. I'm running into conflicting information about seismic weight.

Example: a one story square building, being analyzed the N-S direction. I would have assigned the dead load of the entire roof, plus one half of the weight of all four walls to the diaphragm. However, several example problems I have seen ignore the weight of the walls parallel to the direction of loading (i.e., the east and west walls); they only factor in the weight of the north and south wall. Is this the proper procedure? If so, is there some reference I'm missing?

 

[RobertHale]

I think it is the appropriate procedure. Although I do not have a specific reference, it is just a thought exercise in the load path. It doesn't make sense that the weight of the parallel walls will go out of the wall and into the diaphragm then right back into the wall. This path is based on having a collector element to transfer the weight of the non-lateral walls to the lateral elements. I also think it is important to note that this is only for the diaphragm; the vertical lateral load resisting elements need to be designed for the weight of all the walls. I hope this helps.

 

[JAE]

If you are designing the diaphragm then the parallel wall seismic load does not extend into the diaphragm and then back out again.

If you are designing the main lateral resisting system, then all the walls and mass tributary to each level should be included.

 

[frv]

Thank you, Gentlemen.

Makes perfect sense.