Density for some typical backfill materials:
The acting position of the acting force can be calculated as
da = hs / 3 (1d)
where
da = distance from the bottom of the basement wall (m)
The maximum bending moment acting in the basement wall can be calculated as
Mmax = (Fa hs / 3 ht) (hs + (2 hs / 3)(hs / (3 ht))1/2) (1e)
where
Mmax = maximum moment in the basement wall (Nm)
The position of the max moment in the basement wall can be calculated as
dm = hs (hs / (3 ht))1/2 (1f)
Note! - cracking of a basement wall is likely to occur where the moment is at the maximum. Due to tension reinforcement bars should be concentrated closer to the inside wall.
The forces that keeps the basement wall in position - the force at the basement floor/slab and the force from the 1. floor joists at ground level - are indicated in the figure below.
The resultant force due to the earth pressure acting on a basement wall can be calculated as
Fa = 0.5 K γ hs2 (2a)
The acting position of the acting force can be calculated as
da = hs / 3 (2b)
where
da = distance from the bottom of the basement wall (m)
The maximum moment acting in the basement wall can be calculated as
Mmax = 0.128 Fa hs (2c)
where
Mmax = maximum moment in the basement wall (Nm)
The position of the max. moment in the basement wall can be calculated as
dm = 0.42 hs (2e)
A basement wall with height 2.5 m is backfilled with sand.
The Poisson's ratio for sand is 0.29 and the coefficient of earth pressure can be calculated as
K = 0.29 / (1 - 0.29)
= 0.41
The specific weight for the sand can be calculated as
γ = (1555 kg/m3) (9.81 m/s2)
= 15255 N/m3
= 15.3 kN/m3
The resultant force acting on the basement wall can be calculated as
Fa = 0.5 (0.41) (15.3 kN/m3) (2.5 m)2
= 19.6 kN
The acting position of the resultant force can be calculated as
da = (2.5 m) / 3
= 0.83 m
The maximum moment acting in the basement wall can be calculated as
Mmax = 0.128 (19.6 kN) (2.5 m)
= 6.3 kNm
The position of the max. moment in the basement wall can be calculated as
dm = 0.42 (2.5 m)
= 1.05 m
Forces acting on bodies at rest under equilibrium conditions - loads, forces and torque, beams and columns.
Estimate required concrete footing volume.
Cement, sand and gravel mixtures.
Properties of normal strength Portland cement concrete.
Required thickness of concrete slabs.
Estimate required concrete volume per sq. ft.
Estimate concrete wall volume.
Densities - pound per cubic foot and kilograms per cubic metre - of dirt and mud.
Reinforcing bar - European metric dimensions.
Allowable loads on soil.
Typical weight and composition of soil.
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