The calculation of the load on the foundation

load calculation on the foundation necessary for the proper selection of its geometric dimensions and area of ​​the foundation sole.Ultimately, the correct calculation of the foundation depends on the strength and durability of the building.The calculation reduces to determining the load per square meter of soil, and compared it with the permissible values.

For the calculation you need to know:

• Region in which the building is constructed;
• soil type and depth of groundwater;
• material of which will be implemented structural elements of the building;
• layout of the building, number of floors, type of roof.

Based on the required data, the calculation of the basement or a final check is made after the design of the structure.

try to calculate the load on the foundation of one-floor house, made of solid brick solid masonry walls with a thickness of 40 cm Dimensions of the house -. 10x8 meters.Overlapping basement - concrete slabs, overlapping 1 floor - wood on steel beams.Gable roof covered with metal tile, with a slope of 25 degrees.Region - Moscow region, the type of soil - damp loam with a porosity factor of 0.5.The foundation is made of fine concrete, the thickness of the foundation wall is to calculate the thickness of the wall.

Determination of the depth of laying the foundation

Its depth depends on the depth of frost penetration and soil type.The table lists the reference values ​​the freezing depth of soil in different regions.

Table 1 - Background information on the depth of soil freezing

Checklist to determine the depth of laying the foundation for the region

Depth of laying the foundation in general should be more than the depth of freezing, but there are exceptions, due to the type of soil, theyare listed in table 2.

table 2 - The dependence of the depth of the foundation on the type of soil

depth dependence of laying the foundation of the type of soil

depth of laying the foundation necessary for the subsequent calculation of the load on the soil and determine its size.

determined by the depth of soil freezing on Table 1. For Moscow it is 140 cm In Table 2 we find the type of soil -. Loams.Its depth should not be less than the estimated depth of frost penetration.From this depth of laying the foundation for the house is selected 1.4 meters.

calculation load of the roof

roof load is distributed between the parties to the foundation, which is supported by the wall truss system.For conventional gable roof is usually two opposite sides of a foundation for a hipped - all four sides.Distributed roof load is determined by the projected area of ​​the roof, divided by the area of ​​the loaded side of the foundation, and multiplied by the specific weight of the material.

Table 3 - the proportion of different types of roofing

Checklist - The proportion of different types of roofing

1. Determine the area of ​​the projection of the roof.Dimensions of the house - 10x8 meters, the projected area of ​​a gable roof equal to the area of ​​house: 10 · 8 = 80 m2.
2. foundation length equal to the sum of its two long sides, as the gable roof supported by two long opposite sides.Therefore loaded foundation length is defined as 10 × 2 = 20 m
3. area loaded roof foundation thickness of 0.4 m:. 20 x 0.4 = 8 m2.
4. Coating type - metal, slope angle - 25 degrees, so the design load on table 3 is 30 kg / m2.
5. roof load on the foundation is 80/30 = 8 x 300 kg / m2.

calculation of snow load

Snow load is transferred to the foundation through the roof and walls, so loaded are the same side of the foundation, that when calculating the roof.Calculate the area of ​​snow is equal to the square roof.The resulting value is divided by the foundation loaded side of the square and is multiplied by a specific snow load, a particular map.

table - calculation of the snow load on the foundation

1. length of the ramp to the roof with a slope of 25 degrees is equal to (8/2) / cos25 ° = 4,4 m
2. roof area equal to the length multiplied by the ridge.slope length (4.4 x 10) · 2 = 88 m2.
3. Snow load map for Moscow is 126 kg / m2.Multiply it to the roof area and divide by the area of ​​the loaded part of the foundation 88 · 126/8 = 1386 kg / m2.

load calculation floors

ceilings, as well as the roof, usually rely on two opposite sides of the foundation, so the calculation is based on the area of ​​these parties.The area of ​​overlap is equal to the area of ​​the building.To calculate the load of overlap need to consider the number of floors and the basement floor, ie the floor of the first floor.

area of ​​each overlap is multiplied by the specific weight of the material from Table 4 and is divided into an area laden part of the foundation.

Table 4 - The proportion of overlap

Table weight calculation of overlap and the load on the foundation

1. area of ​​overlap is equal to the area of ​​the house - 80 m2.The house has two floors: one concrete and one - wood on steel beams.
2. Multiply reinforced concrete slab area by the specific weight in Table 4: 80 × 500 = 40,000 kg.
3. Multiply hardwood floor area by the specific weight in Table 4: 80 × 200 = 16000 kg.
4. summarize them and find the load per 1 m2 of the loaded part of the foundation: (40000 + 16000) / 8 = 7000 kg / m2.

load calculation walls

wall load is defined as the volume of the walls multiplied by the specific weight of the table 5, the result divided by the length of all sides of the foundation, multiplied by its thickness.

Table 5 - The share of wall materials

Table - Specific gravity walls

1. area equal to the height of the walls of the building multiplied by the perimeter of the house: 3 · (10 · 8 · 2 + 2) = 108 m2.Displacement
2. walls - this area multiplied by the thickness of it is equal to 108 · 0.4 = 43.2 m3.
3. find the weight of the walls, multiplying the volume by the specific weight of the material from Table 5: 43.2 · 1800 = 77760 kg.
4. basement area of ​​all sides of the perimeter is multiplied by the thickness (2 · 10 · 8 + 2) · 0.4 = 14.4 m2.
5. specific load on the foundation wall is 77760 / 14.4 = 5400 kg.

preliminary calculation of the foundation load to the ground

The load on the foundation soil is calculated as the product of volume of the foundation on the specific density of the material from which it is made, divided by 1 m2 of its foundation.The volume can be found as the product of the depth of the foundation on the thickness.The thickness of the foundation take in the preliminary calculation equal to the thickness of the walls.

Table 6 - Specific gravity material foundation

Table - specific density of the material to the soil

1. basement area - 14,4 m2, laying depth -. 1.4 m basement volume equal to 14.4 · 1.4= 20.2 m3.
2. Weight foundation of fine-grained concrete is: 20.2 · 1800 = 36360 kg.
3. load on the ground: 36360/2525 = 14.4 kg / m2.

calculation of the total load on 1 m2 of soil

results of previous calculations are added together, and the calculated maximum load on the foundation, which will be great for those of his party, which relies on the roof.

Conditional estimated R0 resistance of the soil is determined by tables SNIP 2.02.01-83 "Foundations of buildings and structures."

1. summarize the weight of the roof, snow load, the weight of floors and walls, as well as the foundation of the ground: 300 + 1386 + 7000 + 5400 + 2525 = 16611 kg / m2 = 17 t / m2.
2. Determine the design ground conditional resistance tables SNIP 2.02.01-83.For wet loam with porosity coefficient of 0,5 R0 is 2.5 kg / cm2, or 25 t / m2.

from the calculation shows that the load on the ground is within permissible.