Concrete in compression
Concrete in compression under the base plate is checked according to SP 63.13330.2012, Cl. 8.1.44 – Calculation of reinforced concrete elements for local compression:
\[ N \le \psi R_{b,loc} A_{b,loc} \]
where:
- N – local compressive force from an external load
- ψ – factor equal to 0.75 in case of non-uniform distribution of the local load across the bearing surface
- Rb,loc = φb Rb – design compressive resistance of concrete in case of the local impact of compressive force
- \( \varphi_b = 0.8 \sqrt{\frac{A_{b,max}}{A_{b,loc}}} \) and 1.0 ≤ φb ≤ 2.5 – concentration factor taking into account the triaxial stress in concrete
- Rb = Rbn / γb – design value of concrete axial compressive resistance
- Rbn – normative axial compressive resistance of concrete
- γb = 1.3 – reliability factor for concrete under compression; editable in Code setup
- Ab,loc – application area of the compressive force (bearing area surface) determined by finite element method as area in contact between base plate and concrete block
- Ab,max – maximum design area established based on the following rules:
- gravity centres of areas Ab,loc and Ab,max coincide
- maximum design area is geometrically similar to application area; the slopes are 1 vertical to 2 horizontal.
Transfer of shear
The shear action at the base plate is assumed to be transferred from the column to the concrete foundation by:
- Friction between base plate and concrete / grout
- Shear lug
- Anchor bolts
Friction
If shear load is transferred via friction, SP 43 – G.17 is used to check friction shear resistance:
\[V_f = f \cdot N_c \]
where:
- f – friction factor; editable in Code setup; according to G.17 equal to 0.25
- Nc – compressive force acting on the column base
Shear lug
The shear lug is modeled by shell finite elements and its steel resistance and resistance of welds are checked. However, the concrete edge failure and concrete bearing resistances are not checked and should be verified elsewhere.
Anchors
The tensile forces in anchors include prying forces and are determined by finite element analysis.