huangyhg

lateral resisting systems in hotels?
fellow engineers,
i have recently started designing hotels around the country and am a bit concerned in regards to how the diaphragms are loading the shear walls. i have reviewed existing drawings on many existing hotel designs by others and am perplexed on how the lateral system is truly working. the drawings i have reviewed mostly use the stairwells and elevators shafts as the lateral force resisting system for the entire building regardless of where they are located. to me having an one elevator shaft
somewhere in the middle of a 200' long, multistory building doesn't cut. secondly, how does the diaphragm load this rigid element? in other drawings, there may be a a few shearwalls here and there down the corridor of the hotel with no corresponding exterior shearwalls for the diaphragm to span to. any thoughts would be appreciated.
for concrete floors, the lateral force must be transferred into the shearwall/shaftwall system in one of two ways.
1. the entire force is small enough so that it can be transferred directly from the floor into the wall via bolts, weldplates, etc. you have to check not only the connection between the floor and wall, but also the build-up of shear that occurs in the floor itself near the wall. so if you have a 200 ft. long diaphragm, all its shear has to "escape" from the floor, not through 200 ft., but through the much shorter length of floor next to the wall.
2. if the build-up of shear in the floor is too high for the floor, then collectors should be used to drag in the force to the walls.
many engineers don't like option 1 above, and always use collectors.
some long buildings may use a combination of a central shearwall or braced core to resist the direct shear and moment frames to resist the torsion. on buildings above 60 feet in height, asce 7 requires wind load combinations to look closely at wind loads which produce torsion.
a recent hotel (212' x 64') had stairs and elevators located at each end where we had bracing.
i will preface my remarks by saying they apply to one, two, and three story wood buildings. in the transverse direction, i specifically require that roof trusses be located directly above shear walls, so that the roof truss can transfer the shear to the wall below. i specify how the bottom chord is to be nailed to the wall top plate. i have found that a lot of interior walls are needed to make these things work--using just a stairwell or an elevator would not even come close to working.
daveatkins

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