How to make the design of a Foundation

Foundation is the portion of structure underneath plinth level up to the soil. It is directly connected with soil and it transfers the load of super structure to soil. Normally, it is located under the ground level.

If some portion of foundation is situated over ground level, it is also enveloped with earth filling. This part of structure is not in touch with air, light etc, It is considered as the concealed part of the structure.

Depth of Foundation: Depth of foundation is based on the following points-

1. Sufficient bearing capacity should exist
2. Depth of shrinkage and swelling for of clay soils, because of change in climate that may lead to appreciable movements.
3. Depth of frost penetration for fine sand and silt.
4. Chances of availability of excavation
5. Depth of ground water table
6. Practical lowest depth of foundation should not be under 50 cm. to facilitate subtraction of top soil and deviations in ground level.
7. So, the desired depth of foundation should vary from 1.00 meter to 1.5 meter from original ground level.

Footing: Footing belongs to a structure that is built up in brick work, masonry or concrete under the base of a wall or column for dispersing the load over a extended area.

Width of Foundation/Footings

The width of footings is based on the structural design. For light loaded buildings like houses, flats, school buildings etc which do not contain over two stories, the width of foundation is provided below :-

1. The width of footing should not be under 75 cm for one brick thick wall.
2. The width of footing should not be under 1 meter for one and half brick wall.

Various methods in Foundation Work: The following methods are involved in the foundation works -

1. Excavation of earth work in trenches for foundation.
2. Work out cement concrete.
3. Set the footing for raft or column construction.
4. Arrange Anti termite treatment.

5. Set Brick work up to plinth level.
6. Set Damp proof course on the walls.
7. Refilling of earth around the walls
8. Refilling of earth in the building portion up to the desired height as per plinth level.

For more: http://constructioncost.co/how-to-make-the-design-of-a-foundation.html

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Published By

Rajib Dey

www.constructioncost.co

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Benefits of raft foundation

Raft foundation stands for a type of foundation developed for the reinforced concrete slab having consistent thickness (150 mm to 300 mm) that expands over the large area particularly whole footprint of the building.

It provides support to the columns or walls and transmits the load from structure to large area of ground. Once it is built up, it seems mat of concrete extends over large area, as a result it is also known as mat foundation.

The slab bears the load of entire building and delivers it to ground, so it is assessed to float on ground similar way the raft floats on ground.

Raft Foundation is effective under the following situations :-

When the soil at site contains a low bearing strength, thus load required for being allocated over big area.

When it is ineffective to arrange individual or any other type of foundation. As for instance, when the strip foundation would encompass 50% or more area of building footprint, in such conditions raft foundation is very useful.

When there are chances for unnecessary settlement or differential settlement, when other type of foundation is arranged. In this way, settlement chances are minimized by setting up raft foundation.

When the soil situated below is unstable and might comprise of pockets of easily compressible soil, which may lead to individual footing failure. By arranging raft foundation, this risk is reduced.

If it is required to build up basement, raft foundation is necessary. It’s unreasonable and creates various issues if other types of foundation are arranged except for raft foundation at the time of providing basement. Raft foundation is very suitable for transmitting load and also functions as a floor for basement.

Why raft foundation is necessary if the bearing strength of soil is low?

Generally, it is found that if the soil contains low bearing strength, the raft foundation is arranged at site.

Benefits of raft foundation.

Raft foundation transmits the total load of the building to the soil below.

The deign of raft foundation is simple.
The total load on building (dead + live + other loads + self weight of building and foundation) is estimated.

This total load of building is divided with total area of foundation (i.e. footprint of building). It provides us stress on per sq.m of soil.

For raft foundation the load transfer area of footing is much more as compared to the other types of foundation, therefore, the stress on soil is much lesser, thus it can be avoided by soil having low bearing capacity. The risk of shear failure can also be resisted.

To get more information on raft foundation, go through the following link unsolvedengineering.co.in



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Published By
Rajib Dey
www.constructioncost.co
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Simplify the rectangular & continuous footing design with StruCalc

StruCalc’s footing design module is very useful to create the design of square, rectangular and/or continuous footings.

The footing module can be used to meet size and reinforcement requirements for any concrete footing loaded with pure vertical load. Once a footing type is set, StruCalc will then require what is providing the load; it signifies that the type of column is set for the square or rectangular footing, or the stemwall type for the continuous footing.

As soon as the footing type is provided, then the loads on the footing should be entered. The loads originate from two sources: calculations somewhere in the structure that might leads to reactions from beams, columns, walls, etc., or they might originate from the use of the load calculator. The load calculator will produce loads on the footing depending on the user set floor, roof, and wall loads accompanied by indicating tributary widths or areas.

Just fill in the load options of the calculator and it will automatically workout the Live Load and Dead Load.

As soon as the loads are provided, there exist some supplementary footing/environment information like steel yield strength, concrete compressive strength, soil bearing pressure, reinforcement cover, and reinforcement bar size etc. should have been entered.

StruCalc preloads some common values for the properties stated above, but the user will be able to modify any values that seem to be inappropriate.

Besides, adequate information concerning the column should also be entered while going to perform a square or rectangular footing design.

Now, for creating the designing of a square or rectangular footing, StruCalc will need a depth and a trial footing width (and length for rectangular footing) to be entered. Once, these are entered, StruCalc will check their capability provide the necessary reinforcement.

If the dimensions of the footing are not sufficient, a red bar will be visible in the lower right hand corner of the screen and new dimensions should have to enter. It will be at this point though, that StruCalc will have computed a necessary area for the footing. It will facilitate the user to indicate dimensions to fulfill the required area.

While going to design a continuous footing, then the density of the stemwall and height, along with the footing depth should have been entered. Once they are entered, StruCalc will produce a necessary footing width and the continuous reinforcement that is essential.

For more information, go through the following article www.strucalc.com



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Published By
Rajib Dey
www.constructioncost.co
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