Internal pressures do not contribute to foundation reactions???
Internal pressures do not contribute to foundation reactions???
(OP)
A design example in FEMA 550 says the following:
Determine external pressure coefficients for the various building surfaces. Internal pressures, which act on all internal surfaces, do not contribute to the foundation reactions. For sign conven- tion, positive pressures act inward on a building surface and negative pressures act outward.
I do not follow why they do not contribute to the foundation reactions?
Determine external pressure coefficients for the various building surfaces. Internal pressures, which act on all internal surfaces, do not contribute to the foundation reactions. For sign conven- tion, positive pressures act inward on a building surface and negative pressures act outward.
I do not follow why they do not contribute to the foundation reactions?





RE: Internal pressures do not contribute to foundation reactions???
RE: Internal pressures do not contribute to foundation reactions???
ASCE 7 GCpi is a +/- value. The reactions from a shear wall or moment frame will include the internal pressures?
RE: Internal pressures do not contribute to foundation reactions???
An example is a cylindrical tank storing liquified ammonia or natural gas. The vapor pressure (often limited to about 1 psi) acts against both the dome roof and the flat steel floor. But the roof pulls up on the walls, and the thin flat floor can't hold them down. It is necessary to tie the walls to the ring foundation and use a wide tee footing or deep foundations to resist the uplift.
Another example would be a hangar. Foundations in tension are required to resist the uplift forces the roof generates in the columns. The downward air pressure on the floor can't be mobilized to resist the uplift.
RE: Internal pressures do not contribute to foundation reactions???
RE: Internal pressures do not contribute to foundation reactions???
RE: Internal pressures do not contribute to foundation reactions???
RE: Internal pressures do not contribute to foundation reactions???
I still do not understand how FEMA intended the statement you quoted to be applied.