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Steel Portal Frame EC3 RUNET software
16.13 Foundation
The horizontal reaction acting outwards is resisted in two ways.
1.Passive earth pressure on the side of the foundation. In this case the earth filling and compacting on the side of the foundation must be performed carefully, so that the passive earth pressure is not reduced.
2.A tie cast into the floor slab connected to the base of the columns. This should be considered more safe method to resist the horizontal forces at the base of the columns.
The fundament is designed according to Eurocode 7 EN1997-1-1:2004,
Eurocode 7 Geotechnical design, for stability in vertical download forces as well as uplift forces due to wind or seismic load.
The reinforced concrete design is according to EN1992-1-1:2004,
Eurocode 2 Reinforced concrete.
16.13.1 Design of footing
According to Eurocode 7 §6.5.2. The bearing resistance of the footing Rd must be greater than the design load Vd, Rd>Vd. The bearing resistance Rd=quxA'/q, where qu is bearing capacity of soil and the A' is the effective design area of footing as defined in Annex D of Eurocode 7.
The partial factor for soil properties q is used for the design values of geotechnical parameters according to Eurocode 7 Annex A. EQU STR and GEO limit states, and can be modified in Parameters/Design parameters/NAD parameters/material factors.
Only vertical load A'=BxL
Vertical load N and moment M, A’=BxL’. L’=effective foundation length)
L’=L-2xe), e=M/N (load eccentricity)
16.13.2 Passive earth pressure
Passive earth pressure is the resultant pressure developed by a granular material against some surface, when the latter shifts over a small distance towards the material. The basic assumptions for lateral earth-pressure, using a simplified wedge theory , are set by Coulomb
(1736-1806).
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