Wind Load / Load Path
Wind Load / Load Path
(OP)
I've been working on a big-box retail store with 3-sides CMU walls and a front wall that is conctructed of light gauge materials with a variety fo eifs covers/etc. The roof of the building consists of bar joists/joist girders. Their are two lines of joist girders. One line is supported by interior HSS columns and masonry piers in the side walls. The second line of joist girders are suported on HSS columns and are tight/parralel to the front wall. The joist girders obviously span the two bays (in the front half of the building between both lines of joist girders, and in the rear half of the building between the center line of joist girders and the rear wall. The light gauge framing that forms the front of the building is hanging from the joist girder along the front wall.
The wind loads on the side wall of the building would transfer 1/2 to the foundation & 1/2 to the roof structure. Normally the loading in the roof diagram would transfer to the front and rear walls of the building which would act as shear walls. However, teh front wall of the this particular bldg. is non-existant as a shear wall since the open constraints of teh wall do not allow x-bracing between the columns.
So does the entire wind loading actually only transfer loading to the rear masonry shear wall?? Also does teh attachment of angles between the top & bottom of the josit girder and the front light gauge wall (used to hang the light gauge system) constitute any problems??
Hopefully I'm looking at this laod path situation correctly?? Any help is appreciated.
Chris
The wind loads on the side wall of the building would transfer 1/2 to the foundation & 1/2 to the roof structure. Normally the loading in the roof diagram would transfer to the front and rear walls of the building which would act as shear walls. However, teh front wall of the this particular bldg. is non-existant as a shear wall since the open constraints of teh wall do not allow x-bracing between the columns.
So does the entire wind loading actually only transfer loading to the rear masonry shear wall?? Also does teh attachment of angles between the top & bottom of the josit girder and the front light gauge wall (used to hang the light gauge system) constitute any problems??
Hopefully I'm looking at this laod path situation correctly?? Any help is appreciated.
Chris






RE: Wind Load / Load Path
Just as a side not, if there is a parapet be sure not to take 1/2 of the ceiling hieght plus the parapet - I don't know why, but I have seen a lot of people do this.
RE: Wind Load / Load Path
I am not too clear on your very last question about the angles from the top and bottom of the joist girders, can you be a little more clear?
RE: Wind Load / Load Path
Is wind going to control here, not seismic? Where are you located. For seismic, with no lateral resistance at the storefront, it will throw you out of the realm of the simplified method. You will also be penalized under section 12.3.3.4. So, thinking here, why not add an ordinary steel moment frame(s) at the front window wall - steel tubes. This makes many problems go away and the tube frames are generally deflection controlled.
Mike McCann
McCann Engineering
RE: Wind Load / Load Path
I am not sure that will make the torsion problem go away.
The masonry shearwall is MANY, MANY times stiffer than a moment frame. As such, the center of rigidity in that direction will not move very much.
I guess if this is a flexible diaphragm then the moment frame gets the shear based on trib area instead of stiffness, so that will definitely be beneficial.
ChrisKn-
Is this a flexible or rigid diaphragm?
RE: Wind Load / Load Path
Mike McCann
McCann Engineering