reinforcement detailing for isolated footing

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REINFORCEMENT DETALING FOR ISOLATED FOOTING
@ETCONP SHORT ARTICLE
Figure1. Isolated footings source: - topper
I. መግቢያ/introduction
There are different types of foundation based on number of factors.
The isolated footing is the most simple and popular and simplest types of
foundation used worldwide. Foundation is very important to the building.
Ultimately the entire load of the building is transferred to the ground through the
foundation. Isolated footing are the most commonly used footings for reinforced
cement concrete column because it is simple and most economical. An isolated
footing is used to support a single column. Isolated footings are independent
footings which can provide for each column.
የተለያዩ አይነት foundation አይነቶች አሉ። Foundation የምንመርጠው የተለያዩ
ምክንያቶች አሉ።

ለምሳሌ ፡ -
 የአፈር የመሸከም አቅሙ
 Type of structure
 Purpose of the building
 Types of the soil
እኚ ሁሉ የምንጠቀመውን የ foundation አይነት ይወስናል።
Isolated footing የ foundation አይነት ሲሆን ከሌሎች የ foundation አይነቶች ጋር
ስናነፃፅር ወጪ ቆጣቢ እና ለአሰራር ቀል ያለ በኣብዛኛው ጊዜ የምንጠቀመው የ foundation
አይነት ነው። ይህ የ foundation አይነት ለእያንዳንዱ column አንድ footing አለው።
II. This type of footing is used
1. Column is not closely spaced
 ውድ የ @Etconp ቤተሰቦች የ አንድ ህንፃ column ቢጠጋጋ ምን ችግር አለው?
 Dear @etconp members what if the column are closely spaced?
2. Load on the footings are less
3. The safe bearing capacity of soil is generally high
The isolated footings essentially consists of a bottom slab. There are three basic
types of bottom slabs are
1. Pad footing with uniform (thickness)
2. Steeped footing (with nonuniform thickness)
3. Sloped footing (trapezoidal section)
Figure2.types of isolated footing source:-nptel (National Program on Technology Enhanced Learning

III. REINFORCEMENT DETALING OF ISOLATED FOOTING INCLUDE
1.Concrete cover of reinforcement
According to (INDIAN STANDARD) IS 456-200 the “minimum thickness to main
reinforcement in footing should not be less than 50mm if footing is in contact
with the earth surface directly, and 40mm for external exposed face such as
surface leveling PCC. If the surface levelling is not used, then it is required to
specify a cover of 75milimeteres to cover uneven surface of excavation.” PCC
means plain cement concrete ሌላ ነገር አይደለም lean concrete ማለት ነው።
ህንዶች RC ለማለት RCC፣ Grade beam ለማለት plinth beam ነው ሚሉት።
2.Minimum reinforcement and bar diameter
Minimum reinforcement shall not be less than 0.12 percent of the total cross
sectional area.
The minimum diameter for main reinforcement should not be less than 10mm.
3.Reinforcement distribution in footing
In way RCC footing, the reinforcement is distributed uniformly across the full
width of footing. In two-way square footings, the reinforcement is distributed
across the full width of footing along direction. However for short direction, the
reinforcement is distributed in central band as per calculation below in figure 4.
The rest reinforcement in short direction is distributed equally on both sides of
central band.
Figure3. Two way square footing source: - Bayan Mustafa

Figure 4. Reinforcement distribution in square isolated footing source:-NPTEL
4. DOWEL REINFORCEMENT
Dowel reinforcement is used to tie the isolated footing from above column. With
regard to dowel reinforcement development length, the development dowel bars
in to column and the isolated footing shall be provided clearly shown in design
drawings.
Figure5.isolated footing section source: - topper

5. Lap splice
Splice length of dowel and column reinforcement shall be checked to prevent
bond failure of the dowels in the footing and to prevent failure of the lap splices
between the dowels and the column bars.
Fig6. Anchorage reinforcement source:-NTPEL
FIGURE7. PLAN VIEW OF ISOLATED SLOPED FOOTING SOURCE: - NTPEL

IV. ADVANTAGE AND DISADVANTAGE OF PAD FOOTING
 ADVANTAGE
 Its type of shallow foundation so it requires little excavation
 Can be designed to accommodate tight sights
 Economic due to control of foundation size
 Reinforcement for shear and tension can be added
 Easy to construct
 DISADVANTAGE
 Foundation size can be very large cope with high points load
 Limited foundation suitable to point loads of framed building
 Weak against different settlement that may affect the building
 Deep excavations for foundation would require support to prevent
caving in
 Weakness against uplift force, wind forces and earthquake forces
Source:-AAiT lecture note

V. List of figure
Figure8. Arrangement of bars for isolated footing source:-topper
Figure9. Casting concrete for isolated footing source:-@topper

Figure10. Rigid spread footing and flexible spread footing source:-ntpel
Figure11. Plan view and section for spread footing (uniform) source:-ntpel

Figure12. Plan, section and 3D of spread footing source: - CTCIVIL.IR

FIGURE13. Bar details of spread footing source: - nptel
Figure 15. Sloped isolated footing source:- ntpel

Figure 16. Section and elevation for square, rectangular and circular footing
Source: - ntpel
Figure17.flexible spread footing and rigid spread footing source:-ntpel
Source:-ntpel
Topper
AAiT LECTURE NOTE
CITCIVIL.IR
BAYAN MUSTEFA

reinforcement detailing for isolated footing

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