Basic differences among foundation & footing

Foundation: It is the portion of a building that is built up underneath the ground level and keeps direct contact with sub-strata. It transfers the complete load of the building to the subsoil in which it stands in such a manner that settlement of the soil is not collapsed in shear.

Footing: It is the bottom most part of a vertical structure (column, wall) that finally transmits the weight from walls and columns to the soil or bedrock.

Footing is mainly the segment of foundation of any modern structure.

Variation among footing and foundation

Given below, the basic variations among Footing and Foundation:

1
The footing is a formation that is in touch with the ground.

Foundation belongs to a structure that transfers its gravity loads to earth from superstructure.

2
Footing is analogized with the feet of the leg.
Foundation is compared with legs.

3
The footing refers to a type of shallow foundation.
Foundation is both shallow and deep.

4
Footing comprises of slab, rebar which are made of brickwork, masonry or concrete.
Foundation types comprise piles, caissons, footings, piers, the lateral supports, and anchors.

5
Footing reinforces support to a separate column.
Foundation stands for an extensive support since it provides support to a group of footings as a whole building.

6
A number of footings rest on a foundation.
Foundation is the support that sustains different types of loadings.

7
A footing remains under the foundation wall.
Foundations stand for the basement walls.

8
Footing directly transfers loads to the soil.
Foundation is directly related with the soil and passes it on the ground.

9
All footings are foundations.
Not all foundations are footings.

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Guidelines to provide concrete cover for reinforcement in slab, footing, beam & column

Concrete cover: Concrete Cover is arranged for the reinforcement in Reinforced Cement Concrete. Cover means the spacing among the exterior surface of the concrete to the inserted reinforcement.

Benefits of arranging Concrete Cover: The purpose of covering is to provide protection against erosion. Reinforcement is susceptible to erosion and fire for atmospheric conditions. In case of improper cover erosion and cracks may occur in hardened RCC.

Covering is arranged for each and every component of the building (Slabs, Beams, footings) where the reinforcement is applied. The covering blocks are utilized to retain the reinforcement in exact position as well as providing a covering for reinforcement.

Several Types of Concrete Cover Block: Depending on the type of materials applied, the following types of covering blocks are commonly found -

1. Wooden concrete cover Block
2. Steel concrete cover block
3. PVC Block
4. Cement Masonry concrete cover block
5. Aluminium Block
6. Stones

Conditions for Concrete Cover: Covering differs based on the dimensions of the components (Slab, beam, column, footings, etc.) The conditions for arranging covering in RCC are provided below -

Condition - Covering

When the length of the item is ≤ 0.3 1 - 1" or 25mm or 0.025mWhen the length of the item remains among 0.4m to 0.5m then - 2" or 50mm or 0.050m
When the length of the item remains ≥ - 0.6m then 4" or 100mm or 0.1m

From above, the maximum concrete cover remains 0.1m or 100cm

1. Concrete Cover in Columns / Beams: The length and width of the column should be 0.5m and 0.45m. The covering for reinforcement in the column should be 0.050m from all sides and similar reinforcement should be designed accordingly. The Dimensions of Reinforcement in the column should be 0.40m and 0.35m.

Suppose the length and width of the column are 0.40 and 0.25. Covering should be equal. Consider the minimum dimension from the two dimensions i.e. 0.25. For 0.25m the covering of 0.025m should be provided. So, the covering of 0.025m is arranged in all the sides. Therefore, dimensions of reinforcement is 0.35m and 0.20m.

Total Length of Stirrup is 2x [0.35+0.20]+ 9D x 2 (hook length)

2. Concrete Cover for Slabs: Suppose, the length and width of the slab are 1.3m and 1.0m. The covering of 0.1m is arranged when the length of the bar is in excess of 0.6m. Use the same condition as mentioned. The covering of 0.1m is arranged from all the sides of the slab.

3. Concrete cover for footings: Suppose, the dimensions of Footing are 0.7m and 0.6m. To length and width of Mesh (reinforcement) utilized in footings are acquired by subtracting the cover. Use the similar principle as above. As per the condition, a concrete cover of 0.1m is subtracted from all the sides. Therefore, the dimensions of reinforcement are 0.5m and 0.4m.

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Construction Method Of Concrete Slab On Grade

Slab on grade belongs to concrete floor slabs which are poured at grade or ground level to develop a foundation for a home. Prior to start the construction, contractors excavate the soil adjacent to the area where the foundation should be constructed and ensure that the ground has sufficient strength to support the structure.

Normally, the periphery of the slab is very dense as compared to the rest of the surface. This section has similarity with footer that facilitates to circulate the weight of the exterior walls uniformly over the soil underneath the structure. Slab on grade foundations are suitable for the areas where the soil is unusable for crawl spaces or basements.

Grade slabs are provided in areas where the ground is not solidified. This type of slabs may or may not include reinforcement in it. The inclusion of reinforcement depends on the floor loads and local building codes.

The thickness of Grade Slab should be at least 4 inches. If porosity exists in soil, the thickness of the slab should be raised. To maintain safety, a layer of gravel & bitumen should be placed on earth prior to arrange concrete slab to stop the penetration of moisture content into the slab.

Slab on Grade is categorized as follow:

1. Supported Slab on Grade
2. Monolithic Slab on Grade

Supported Slab on Grade / Grade Slab: Supported grade slab or slab on grade foundation should be used when the conventional footings are already set up on site to uplift the columns. Under this system, the wall is laid on a footing and the grade slab stands on a layer of gravel and moisture barrier.

The formwork applied for plinth beams operates as batter boards for slab mould. There is an expansion joint among concrete slab and wall to reduce the stress throughout high-temperature days. Control joints are set in a planned grid with chalk lines to manage occasional cracking on the slab.

Monolithic Slab on grade: There are no footings for monolithic grade slab, the concrete slab itself functions as a footing for the building; and the columns, walls are uplifted from the grade slab. This type of slab is structured with batter boards around the slab based on the plan and the concrete is poured inside batter boards. These batter boards operate as a mould to detect the slab corners.

Grade slabs normally stand on the layers of gravel and moisture barrier. These layers can resist penetration of water into the slab to develop surface cracks.

The periphery of the grade slab is very dense as compared to the rest of surface. This dense section operates as a mini footing and facilitates to circulate top loads more consistently over the adjacent soil.

Construction Method: Prior to cast slab on grade, the excavation of earth is done to the desired depth along with compaction to drive out air voids. Batters are leveled and provided in exact location based on the plan prior to concrete pour. These boards function as a concrete mould to facilitate detecting the slab corners.

After that, soil investigation is performed to design the thickness of the slab. After obtaining the results, the layers of gravel and moisture barriers (bitumen) is again poured on the ground. These layers are used as a sub-base for slab and resist the infiltration of moisture into the slab.

The thick concrete is poured at the edges to form an solid footing and reinforcement rods are placed to increase the strength of the edges.

To reduce random cracking on the surface, the concrete should be cured and dried for long times.

The expansion joint should be arranged among the wall and slab. The control joints on the slab are leveled with chalk lines prior to pouring which can check random cracking.

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Sample quotation for constructing an indoor badminton court

In this civil engineering article, you will get a sample quotation with quantities of construction material to design and develop an indoor badminton court.

SPECIFICATIONS: MAIN FEATURES –

• The structure should contain a basement height of 1’0” from Natural ground level.
• Footing pit size 4’x4’x6’-10mm dia @8” c/c main, 8mm dia @8” c/c alternate.
• Column size – 9”x9” (6 nos 16mm dia and stirrups 8mm dia @8” c/c)

• Plinth size – 9”x9” (4nos 12mm dia main reinforcement and stirrups 8mm dia @ 8” c/c)
• Brickwork should be done with superior quality chamber bricks containing cement mortar in 1:6.
• Basement height 2’-0” Basement inside filling with soil. Over the soil PCC is laid with 1:4:8 with 40mm blue metal.
• Plastering with cement mortar 1:4 exterior wall.
• One coat of white cement and two coats of Asian exterior emulsion should be applied.
• Grano flooring with blue metal chips over PCC in the basement.

THE FOLLOWING MATERIALS ARE UTILIZED:–

• CEMENT: Dalmia/Ultratech/Ramco
• BRICKS: Chamber
• STEEL: ISI
• SHEET: JSW CCGL0.47
• PAINT: ASIAN Paint

Total Area of the Building is supposed to be 54’-0” x 54’-0” = 2916.sq.ft.
Subject: Metal Roofing Shed
‘A’ Truss Length x Width: 58’ Feet x 54’ Feet =3132.Sq. Ft
CLADDING WORK (27’x54’) + (27’x54’) + (30’x54’) + (30’x54’) =6156. Sq. ft

Sub: Fabrication and construction of traditional steel structure with Cooler coated Galvalume.

Columns: Delivery and installation of 12 Numers.150×100 Columns (MS I BEAM Height 32’ Feet) Columns Base Plates should have 20 mm thickness 300 mmX300mm & Columns top Plates should have 8 mm thickness.

Base foundation 25 mm 1’5’Feet 48 Numbers
Columns Bracing Support ( X 4 Numbers)

A Type Trusses: Delivery and installation of of 4 Numbers. Trusses 54.0” Feet span formed 50X50mm MS Square Pipe Bottom Rafter as 50X50mm MS pipe with inner cross 30X30 Straight as 30X30 mm pipes medium (ISI 2mm thickness) Lighting Support 1 No Inclusive.

Paint Works: One coat of premier & two coats of enamel paint.

Roof Sheet: Color coated Galvalume CCGL JSW sheet (0.47mm) and its accessories.

Purlin > 60×40 (ISI 2mm thickness) Square Tube purlin.(1000+1300=1Numbers)

To get more details, click on the following link www.onlinecivilforum.com

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Some vital tips to develop a column independently

A column footing generally stands for a block of concrete that is poured in the bottom of a hole with the purpose of allocating the weight provided on the column to a greater area. As a result, the columns can’t go down into the ground in due course. Given below, some useful guidelines to pour the footings independently.

Step 1 - Measure the Footing: Label the spot to locate the correct center point of the column.

After that, work out and mark out a square that is 12 inches larger regarding the size of the column, and excavate the hole. Standard depth should be 12 inches along with one extra inch for each three inches of column. As for instance, the minimum depth should be 14 inches for a six-inch column. More is always recommended.

Step 2 - Level the Bottom: The bottom of the hole should be leveled. If it is not possible to work with a shovel because of shortage of space, utilize a concrete trowel.

Then, take the measurement from the bottom 12 inches along with the depth added for column size, and fix a nail into the side of the hole at that depth on all four sides. Instead, provide a stake into the bottom of the hole, leaving that amount of the stake uncovered.

Step 3 - Measure the Concrete required: Cut a piece of wire mesh as per size of the hole, and put aside. It is assumed that minimum one full bag of concrete should be needed for the column footing or possibly more, but the formula for making perfect measurement is L x W x H / 12 to obtain the result for the number of bags required, rounded up. The height should be the distance from the bottom of the hole to the nails (or the top of your grade stake).

While arranging a column permanently, work out the concrete to fill the hole to within three inches of the top. Apply a mix containing small rocks in it since these rocks will arrange reinforcement and avoid cracking.

Step 4 - Pour the Footing: Mix the concrete based on your calculations. It is suggested not to mix excessively than required amount to fill the hole up to the nails at this time. It will be the actual footing and it should be poured discretely first, prior to adding the permanent concrete setting. Shovel or pour the concrete into the hole, but take precautions not to cave in the sides. Set the wire mesh down into the concrete, roughly halfway to the bottom.

The finishing of the surface should be smooth, but not slippery. Employ the nails as a guide for the finish depth along with them hardly over the top of the footing.

As these nails are only a guide, therefore, apply a torpedo level for leveling the footing. Allow a footing to be cured for minimum 48 hours prior to setting the column.

Step 5 - Set the Columns: While setting permanent columns, arrange one end on the footing after it is cured. Brace the column to retain it perfectly in vertical direction while checking on all sides. After that, mix the remaining concrete from your calculation and fill the hole upto three inches of the top.

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Simple process to calculate shuttering materials for footing

There are various types of formwork materials can be used for footings. You can use plywood, wooden plank or even steel shutter.

Mostly used shutter materials for footing is wooden planks, plywood or wooden board as those are cheap and widely available.

How to Easily Estimate Shuttering Materials for Footing

There are different types of footings in a building. But, all the footings are different. There should be equivalent types of footings. Initially, it is required to summarize the similar type of footings.

Summarizing footings - Generally, the footings are demarcated as F1, F2, F3… etc.

Presume, there are 10 numbers of F1 type footing, 6 numbers of F2 type footing, and 8 numbers of F3 type footing, etc.

Summarize them all. The same types of footings will be summarized based on the footing layout drawing sheet. It is accessible in the structural drawing book.

Once the counting is done for all types of footings, verify the footing layout drawing to find out whether any footing remains unmarked. If there is any, count it also.

Once this step is completed, you’ll get the numbers of all types of footing.

Now, the total number of footings should be counted in the footing layout drawing by marking individually with the pencil.

It is not necessary, to create formwork for all the footings. As for instance, there are 10 numbers of F1 type footings. The sizes of all these footing are equivalent. If you only create one formwork for this type, that can be used again for all 10 footings. In this way, the cost will be saved significantly.

To reduce the cost, it is recommended to utilize wooden shutter materials for footing instead of steel shutter for footings.

Given below, the detail method to measure wooden shutters materials for the footing of a building project.

Step 1: Work out the Periphery Length of Footing.

Assume, the size of the F1 footing is, 4′ x 6′ x 1′.
Therefore, the periphery length of this footing will be as follow :-
= (4′+6′) x 2
= 20′
Step 2: Work out The Periphery Area of The Footing
The periphery area of the F1 footing is,

=20′ x 1′ (the height of the footing is taken as 1′)
= 20 square feet (sft)

Step 3: Workout Shuttering Materials

Wooden plank or plywood : The periphery area of the F1 footing is actually required area of wooden plank or plywood that is 20 square feet. It is required to include 5% extra while giving order for wooden plank or plywood. Therefore, necessary wooden plank or plywood for our footing is, 21 sft.

Wooden batten: Usually, 3″x 2″ wooden batten for the formwork of footings is utilized. To make the process simple for calculating wooden batten, just use a thumb rule that is 2 rft (running feet) per shuttering area. So, required wooden batten for the footing will be as follow :-

= 2 x 21
= 42 rft (running feet)

Nail: Similarly, to calculate nail for formwork, just use a thumb rule that is 0.02 kg for one square foot of shuttering area.

Therefore, the required nail for our example footing is,
=0.02 x 21
=0.42 kg (kilogram).

So, the necessary shuttering materials for one formwork of F1 type footing are obtained. Depending on how many formworks will be required for F1 type footing, multiply the shuttering materials with that number.

As for instance, if there are 10 numbers of F1 type footing and it is necessary to create 3 numbers of formwork for this type footing, required shuttering materials for 3 numbers of formwork for F1 type footings will be as follow:-

• Wooden plank or plywood = 3 x 21 = 63 sft
• Wooden batten (3″x2″) = 3 x 42 = 126 rft
• Nail = 0.42 x 3 = 1.26 kg.

In the same way, work out the shuttering materials for all several types of footing for your building project and summarize them all.



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Importance of pre-pour cards for concrete placement

Pre-pour checklists are very crucial for proper concrete placement. There should be an authentic verification and checking method to make sure that your next concrete placement is accurate. Without a pre/post pour checklist, huge is money is lost due to inappropriate lighting, incorrect mix design, slump, spacing, manpower etc.

In a pre-pour checklist, the following items should be included :-

1. Fill out as soon as the pour is already finished.
2. Fill it out 5 minutes prior to the pour
3. Left blank
4. Don’t have/use one.

Then it is required to re-assess what a good pre-pour checklist can achieve.

To make a pour card effective, the perfect process should be developed while running through the checklist. A perfect pre-pour process will achieve all the steps and the: Who, What, When, Where, How”.

Who: has verified, examined, checked, and figured: yardage, elevations, sleeves, anchor-bolts, embeds, reinforcing, elevations, mix design etc.

What: is being placed, size of pour, manpower required (footing, wall, column, SS, SOG, S.O.M.D)

When: is the pour occuring (Date, Time, truck spacing)?

Where: (Placement location, pump truck setup, truck route, wash out bin)

How: is it being placed (pump, screeds, equipment, lighting, safety, etc.)?

The pre/post pour cards facilitate a simple check and verifications. While a detailed assessment and paying special attention to detail and passing through all the steps to checkoff is accomplished, it will save your significant time and money and re-work as well as allow you planning and performing a effective pour.

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Plum Concrete – Usage and Construction Process

Definition of Plum Concrete: It is formed by amalgamating coarse aggregate and cement which are set underneath the foundation or footing of a structure in order to attain a level surface for allocating the load equally.

The plum concrete is actually an inexpensive variation of mass concrete.

The plum concrete is suitable when the desired thickness of PCC is extreme or large.

It is primarily provided under the foundations where the quantity of leveling course could be too much because of steep slope of the strata.

Usages of Plum Concrete:

1. The plum concrete is applied underneath the footings of residential buildings with small portion where the slope of ground under single footing is 1:10 to 1:50 in order to save the cost of concrete. It leads to huge reduction of the overall construction cost of the building.

2. Plum Concrete is also suitable in areas where considerable concrete placements like concrete dams or bridge piers are necessary. Under these types of situations, pieces of rock about 150 mm in size are utilized as coarse aggregates to blend a plum concrete.

Construction Process of Plum Concrete:

Step 1 – Transportation of Plum Material
The boulders contain large Stone size which are simply upraised by laborers, not too big or small.

Step 2 – Leveling and Cleaning – Arrangement Of Surface
Preliminary, the surface should be perfectly leveled and cleansed by eliminating soft soil that can produce low bearing capacity. As soon as clearing and grubbing are completed, water is sprinkled to the surface to keep it wet prior to arrange plum concrete. The purpose of sprinkling water is to retain exact bond of plum concrete with the ground surface. As soon as the water is sprinkled, anti-termite chemical is sprayed to keep the foundation of the structure undamaged.

Step 3 – Pacing and expanding of Plum Concrete
Boulder’s are put on the ground layer by layer with little spacing and concrete is distributed with pump all over the boulders in each layer that gradually penetrates inside the spacing among boulders. It allows tying it perfectly, once the concrete is poured, boulders are provided to the concrete again and the process is reiterated till desired level surface is attained.

Step 4 – Curing of Plum Concrete
Curing should be accomplished for at least next 7 days. Jute bags are laid on the entire area of plum concrete to keep moisture for a prolonged period after curing.

Boulder’s should be examined prior to spreading and if any dirt or Clay is detected, then it should be cleansed perfectly. Boulders should be well-built and should not be flaky as the load from entire building will be enforced upon it. Sometimes, more boulders are required in case of shortage of concrete or for economical purpose etc.

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Reasons for failure of bearing capacity on foundation

Foundation failure occurs due to variation on the load:

There exist three types of shear failure, i.e. General, Local and Punching shear failures which happened due to the compactness of soil and depth of footing with regard to its breadth (i.e D/B Ratio). When the utmost capacitybearing  of the soil is attained, it may fail in one of the following three failure type on the basis of the type of soil and depth to width ratio of the footing. A foundation can collapse in the following three diverse ways under loads :

Punching shear failure of foundation

General Shear Failure of foundation

Local shear failure of foundation

The above three types of foundation failure should be examined throughout design phase of concrete foundation for the specified load. Directives obtained through standard codes of practice should be obeyed so that foundation does not fail in any of the failure types as stated under any probable load combinations when structure is in use.

1.General Shear Failure

• Under this type, the footing moves downward slightly and thus forms completely plastic zones and a sudden failure occurs with a significant bulging of the ground surface alongside the footing
• It is based on clear-cut failure pattern, that comprised of a wedge and slip surface and bulging (heaving) of soil surface alongside the footing
• Sudden collapse happens, together with tilting of the footing
• This type of failure happens provided that dense sand or stiff cohesive soil support the footing
• Failure load is apparent
• The load-settlement diagram is equivalent to stress-strain for solid sand or over-consolidated clay
• The ultimate load is apparent on this curve.

2. Local shear Failure:

Failure pattern comprises of wedge and slip surface but is transparent only under the footing. Slight bulging of soil surface takes place. Tilting of footing is not necessary.

• In this mode a large deformation takes place under the footing prior to the formation of failure zones, i.e. large vertical settlement occurs prior to slight bulging of the ground surface
• Tilting of footing is not necessary
• Ultimate load is not clear
• It occurs in moderately compressible soils or loose sand i.e occurs in soil of high compactness
• Yielding occurs adjacent to the lower edges of the footing
• Various yield developments may happen together with settlement in a series of jerks
• The bearing pressure at which the first yield occurs is assigned as the first-failure pressure or first failure load

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Detailed information on Shallow Foundation

Shallow foundation

A shallow foundation is defined as the foundation that transmits the building loads to the earth adjacent to the surface. It’s depth is equivalent to or under its width.

Categories of shallow foundation:

1. Spread footingThe role of Spread footing is to extend the super imposed loads of the structure over a extensive zone.

Spread footing is subcategorized as below :

• Single footing for a column.

• Stepped footing for a column.

• Sloped footing for a column.

Concrete is utilized to create the base of these types of footings.

• Wall footing without steps and with steps.

• Grillage foundationgrillage foundation is considered as most cost effective while transmitting the heavy structural loads concerning a column to the soil of low bearing capacity. Depth of such a foundation is restricted to 0.9 to 1.6 meter.

2. Combined footing

The combined footing is developed for two or more columns.

Shape of combined footing is balanced in such a ratio so that the center of gravity of the supporting area remains consistent with the center of gravity of the two column loads. It is formed as either rectangular or trapezoidal.

A combined rectangular footing is useful where both the columns bear identical load or interior column bears superior load. A combined trapezoidal footing is arranged under any situations of loading.

3. Strap footing Strap footing is undertaken when two or more footings are associated with a beam. It is required when the distance among the columns is so excessive that a combined trapezoidal footing turns to be little constricted, containing great bending moments.

4. Mat or Raft foundation Mat or raft foundation is described as a consolidated reinforced concrete slab that covers the entire region of the bottom of the structure.

Mat or raft foundation is useful in the following conditions :-

• If the soil located below contains bearing capacity as well as the building loads are substantial.

• If the combined area of individual footing exceeds half of the total area of the structure, then application of mat or raft foundation will be cost effective.

Article Source : www.civilengineeringterms.com

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How to measure Reinforcement with column & footing

This construction video provides step-by-step guidelines on estimation of Reinforcement with column and footing as per construction drawing. The video will be very useful for foundation design.

Reinforcement is essential for reinforced concrete members like footings, beams, columns, slabs, lintels etc. It is recommended to estimate reinforcement quantity before tendering phase for measuring cost of project or construction work roughly.

If working drawings and schedules for the reinforcement are unavailable, then it is required to create an estimate of the projected quantities. The quantities are usually defined according to the requirements of the Standard method of measurement of building works.

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Different types of foundation and their usefulness

Maximum structures are built with two parts like super structure and sub-structure of the foundation. Super Structure is located over the ground and the other sub-structure of the foundation is located beneath the ground level. Foundation alias footing of a structure associates and transfers the load from the structure to the ground soil. The foundation is developed on the solid ground and it is called as the foundation bed. The foundation transfers the load of the structure and it’s self-weight to the soil with the purpose of keeping the final bearing capacity of the soil under control (the shear failure does not occur) as well as keeping acceptable settlement.

All the structures have foundation at the base that offers the following functionalities:

• To disperse the load of the structure across an extensive bearing area.
• To load the bearing surface equally to get rid of asymmetrical settlement.
• To resist the lateral movement of the supporting material.
• To enhance the strength of the structure all together.

Foundation is based on the following points :-

Foundation is categorized depending on the dispersion of load to the ground into two sub-categories like shallow foundation and deep foundation.

Shallow Foundation

Shallow foundation belongs to the foundations where depth of the foundation remains below the width of the foundation (D < B). Shallow foundations are usually known as spread footing because they transfer the load of the super structure laterally into the ground.

Categorizarion of Shallow Foundation:

Based on the design, the shallow foundation is classified as:

• Wall Footing
• Isolated column or Column Footing
• Combined Footing
• Cantilever (Strap) Footing
• Mat (Raft) Foundation
• Wall Footing

This type of foundation runs consistently along the direction of the wall and facilitates transferring load of the wall into the ground. Wall footing are mostly applicable where transferable loads are small and cost-effective in compact sands and gravels. For this type of foundation, the width remains 2-3 times the width of the wall at ground level. Wall footing is built up with stone, brick, plain or reinforced cement concrete.

Column Footing

Column footing are useful and inexpensive for the depth surpassing 1.5m. For this type of foundation, the base of the column is distended. Column footing comes in the shape of of flat slab and is developed with plain or reinforced concrete.

Combined Footing

Combined footings belong to the foundations which are built in common for two or more columns in a row. It is generally formed if the footing for a column is spreaded outside the property line. It is applicable if the two columns are placed narrowly and the soil on which the structure is developed contains low bearing capacity. The shape of the combined footing appears as rectangular or trapezoidal.

Strap Footing

If an edge footing fails to spread outside the property line, it is connected with the other interior footing through a strap beam. Such footings are defined as strap footing. or sometimes cantilever footing.

Mat Foundation

A mat foundation belongs to a combined footing that covers the whole area below a structure and supports all the walls and columns. It is also called as raft foundation. Mat foundation is mostly suitable for the following reasons:

Permissible bearing pressure is low.

The structure is weighty.

The site is located with highly compressible layer.

The mat foundation is categorized into following types:

Flat slab type.

Flat Slab thickened under column.

Two way beam and slab type.

Flat slab with pedestals.

Rigid frame mat.

Piled mat.

To read the complete article, visit civileblog.com

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