Are foundation stem walls part of seismic resisting system?

[McSEpllc]

Hi Everyone,

Currently I am working on a single story, 16,000 SF medical center that is a non-essential facility for building occupancy in Western North Carolina. Per the geotechnical testing the seismic site class is ‘E’. The construction will be residential type stick-framed walls and pre-engineered wood trusses. The floor will be a slab on grade with CMU stemwalls on continuous wall footings. There will be interior stick-framed load-bearing walls bearing on thickened slab footings. My intent is to use light-framed plywood shear walls of interior and exterior walls as the lateral load resisting system

My Question: Are the CMU stemwalls part of the load resisting system? If the CMU stemwalls were part of the load-resisting system, they would need to be ‘special reinforced’ to meet the requirements for site class ‘E’ per ASCE 7. I can reason that if the friction that can develop between slab and grade due to building dead loads, using the 1.5 safety factor against sliding, is in excess of the seismic base shear load, the slab is the more direct load path for seismic loads.

What are your thoughts?

Thanks!


Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[msquared48]

If the lateral loads enter shear wlls that are connected to the CMU stemwalls via anchorbolts and holddowns, then they are part of the lateral resisting system. If not, then no.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com