1、 Design of independent foundation under rigid frame column

1. characteristic value of foundation bearing capacity and foundation material

The geological conditions of the project are as follows:

000m ~ – 0.6m, the backfill contains humus, γ = 16kn / m3, FAK = 80KN / m2, e = 300N / mm2;

For general loam, γ = 20KN / m3, FAK = 230kn / m2, e = 500N / mm2;

Below – 2.70m is weathered mixed soil, FAK = 300KN / m2, e = 600 ~ 1000N / mm2;

The groundwater level is at – 5.0m.

Considering the use of the building, the type of foundation, load size, engineering geology and hydrogeological conditions, the bearing stratum is considered as general clay layer, FAK = 230kn / m2, and the embedded depth of foundation is 1.0m.

Assuming that the foundation width is less than 3m, the FAK is modified according to formula 5.2.4 of code for design of building foundation (GB 50007-2002)

fa=fak+ηbγ(b－3)+ηdγm(d－0.5)

=230+1.6×[(16×0.6+20×0.4)/1.0]×(1.0－0.5)

=244.1KN/m2

The foundation is made of C20 concrete, FC = 9.6 n / mm2, ft = 1.10n/mm2

The reinforcement is hpb235, FY = 210n / mm2, the thickness of concrete cover for reinforcement is 40mm, and the cushion is made of C10 concrete, with thickness of 100 mm.

2 Calculation of internal force and area of foundation bottom
The design value of internal force of column bottom section with basic load combination: n = 102.82kn, v = 32.21kn, M = 0; corresponding internal force value of standard load effect combination is: NK = 81.18kn, VK = 25.06kn, MK = 0

The conical foundation is adopted and the foundation height H0 = 400mm is assumed,

According to (1.1 ~ 1.4) A0, the bottom area of eccentric compression foundation is estimated a: a = (1.1 ~ 1.4) × 0.36 = 0.40 ~ 0.50m2, a = BL = 1.5 × 1.0m = 1.5m2, w = 0.375m3. The shape, size and layout of the foundation are shown in the figure.When GK = 24 × (1.5 × 1.0 × 0.4) + 16 × (1.5 × 1.0 × 0.6) = 28.80kn, the internal force value of standard value combination of corresponding load effect on the foundation bottom surface is: NK = 81.18 + 28.80 = 109.98knmk = 25.06 × 1.0 = 25.06kn · M. the checking calculation of the pressure on the bottom of foundation is: NK = 81.18 + 28.80 = 109.98knmk = 25.06 × 1.0 = 25.06kn · M

2 FA = 292.92kn / m2 > pkmax, pkmin > 0, (pkmax + pkmin) / 2 < FA,

Therefore, the size of the foundation bottom surface meets the requirements.

The foundation design grade of the project is considered as grade C. according to the specification, the foundation can not be checked for deformation.

3 Check the punching shear bearing capacity of the foundation with variable order

According to the basic combination of load effect, the net reaction of foundation bottom is obtained as follows:

N=102.82KN，M=32.21×1.0=32.21KN·m，e=M/N=0.313m

The distance between the action point of N resultant force and the maximum pressure edge of foundation bottom surface a = 1.5 / 2-0.313 = 0.437m

pnmax=2N/(3la)=2×102.82/(3×1.0×0.437)=156.86KN/m2

Then I-I section at the junction of column and foundation is as follows:

PN = 100.03kn/m2, H0 = 400-45 = 355mm, at = 300, ab = 300 + 355 × 2 = 1010mm > L, ab = 1000mm, am = (at + AB) / 2 = 650mm, Fu = 0.7 β hpftamh0 = 0.7 × 1.0 × 1.1 × 650 × 355 = 177.7 × 103n = 177.7knfl = pjal = 156.86 × [(1.5 / 2-0.55 / 2-0.355) × 1.0] = 74.5kn < Fu, meeting the requirements.

4. reinforcement calculation of foundation bottom surface

Optional 8 φ10@200，As=628mm2。

The reinforcement of foundation is shown in the figure.

The foundation short column is reinforced according to the structure.

2、 In the design of independent foundation under the wind resistant column of gable, the load borne by the wind resistant column and the engineering geological and hydrogeological conditions are considered. Referring to the design results of the rigid frame column foundation, the buried depth of the wind resistant column foundation is d = 1.0m, the base size is B × L = 1.0 × 1.0m, and the reinforcement of the foundation slab is selected as 6 φ according to the structure10@200。The experience calculation meets the design requirements.

3、 Design of extended foundation under wall

1. basic information

Mu10 mechanism solid clay brick wall and M5 cement mortar masonry are adopted for the exterior wall of the project below + 1.200m elevation, and double-layer color profiled steel plate is used above + 1.200m elevation.The middle of the steel plate is filled with 50 mm thick glass wool board.Considering the load conditions and geological conditions, C15 concrete unreinforced foundation is adopted, the elevation of foundation bottom is – 1.100m, and the thickness of concrete foundation is 30mm.

2. load calculation

Double layer color profiled steel sheet 0.30kn/m2

50mm thick glass wool board 0.05kn/m2

Total 0.35kn/m2

Since the weight of aluminum alloy doors and windows is similar to that of color plate wall, the area of door and window opening and the weight of doors and windows are not deducted when calculating the weight of color plate wall.The standard value of linear load from color board wall to brick wall is as follows:

0.35(7.2-1.2) = 2.10kn/m240mm thick mortar ordinary brick 0.24 × 18 = 4.32kn/m218mm thick cement mortar plastering internal and external walls 0.018 × 20 × 2 = 0.72kn/m2

Total 5.04 kn / m2

Then the standard value of dead weight line load of brick wall is 5.04 × (2.0-0.18) = 9.17kn/m

Self weight of ring beam: 0.24 × 0.18 × 25 = 1.08kn/m

The standard value of permanent line load transmitted to the top of foundation is 2.10 + 9.7 + 1.08 = 12.35kn/m

3. determination of foundation bottom width

If the width of foundation is 500mm, take 1m long foundation for calculation:

=39.0kn / m2 < < FA = 244.1kn/m2, meeting the requirements.

The width height ratio of foundation: B2: H0 = 70 / 300 = 0.23 < 1:1.25, meeting the requirements.

4. check the bearing capacity at the bottom section of brick wall

H0=2H=4.0m，μ1=1.2，μ2=1.0，

Height thickness ratio:

H0 / h = 4.0 / 0.24 = 16.7 < μ 1 μ 2 [β] = 1.2 × 1.0 × 24 = 28.8, meeting the requirements.