Design Of Foundation for a Commercial and Residential Building

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Design Of Foundation for a Commercial and
Residential Building
An-Najah National University Engineering
Collage Civil Engineering Department

• Under the Supervision of
• Dr. Mohammad Ghazal
• Prepared by
• Moayad Qadarah
• Rajae Omar
• Luai Abu Sharshuh

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Project Description

• Name Eisheh Taha Oudeh Building.
• Type commercial and Residential Building.
• Location Nablus City, Rafedia Main Street,
  opposite to Ben Qutaiba School.
• Number Of Floors 12 floor, 2 under ground level
  and 10 over.
• Plane Area 550 m2 for the floor.

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SCOPE OF PROJECT

• Evaluation of foundations.
• Selection of the proper foundations.
• Design of foundations.

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Literature Review

• Foundations are the part of an engineered system
  to receive transmit loads from superstructure
  to the underlying soil or rock .
• There are two types of foundations shallow
  deep foundations.
• Many factors should be taken into consideration
  in choosing foundation types such as soil
  properties , economic factors, engineering
  practice, ....etc

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Types of footing

• Isolated Footing.
• Combined Footing.
• Mat or Raft Foundations.
• Strap or Cantilever Footings.
• Pile Foundations.

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 Isolated Footings

• Are used to support single columns.
• This is one of the most economical types of
  footings and is used when columns are spaced at
  relatively long distances.
• Its function is to spread the column load to the
  soil , so that the stress intensity is reduced .

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Combined Foundations

• Are used in the following cases
• 1) When there are two columns so close to each
  other in turn the two isolated footing areas
  would overlap.
• 2) When the combined stresses are more than the
  allowable bearing capacity of the soil.
• 3) When columns are placed at the property line.

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Mat or Raft Foundations

• Are used to spread the load from a structure
  over a large area, normally the entire are of the
  structure .
• They often needed on soft or loose soils with low
  bearing capacity as they can spread the loads
  over a larger area.
• They have the advantage of reducing differential
  settlements.

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Strap or Cantilever Footings

• Cantilever footing construction uses a strap beam
  to connect an eccentrically loaded column
  foundation to the foundation of an interior
  column .
• Are used when the allowable soil bearing
  capacity is high, and the distances between the
  columns are large .

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Pile Foundations

• They are long slender members that are used
  to carry transfer the load of the structure to
  deeper soil or rocks of high bearing capacity,
  when the upper soil layer are too weak to support
  the loads from the structure.
• Piles costs more than shallow foundations so
  the geotechnical engineer should know in depth
  the properties conditions of the soil to decide
  whether piles are needed or not.

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Bearing Capacity

• Bearing Capacity is the ability of a soil to
  support the loads applied to the ground .
• Ultimate bearing capacity is the theoretical
  maximum pressure which can be supported without
  failure
• Allowable bearing capacity is the ultimate
  bearing capacity qu divided by a factor of safety
  (F.S).
• There are three modes of failure that limit
  bearing capacity general shear failure, local
  shear failure, and punching shear failure.

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Settlement

• When building structures on top of soils, one
  needs to have some knowledge of how settlement
  occurs how fast settlement will occur in a
  given situation.
• So, There are three types of settlement
• 1. Initial settlement
• 2. Primary settlement
• 3. Secondary settlement

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Settlement (Cont.)

• Total Settlement SI SC SS
• The allowable bearing capacity and the type of
  foundations provided later are evaluated based on
  the settlements limits. This means that the
  settlement of the proposed foundation would be
  within the acceptable limits if the allowable
  bearing capacity provided is used.

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Geotechnical Investigation

• The studied area is approximately flat with
  slight difference in the three existing
  elevations. The general soil formation within
  Highly fragmented weathered limestone and
  marlstone of soft to medium strength with
  cavities filled with marl soil

• The geotechnical engineer decided to drill Three
  boreholes trying to cover the whole construction
  area.

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• The depths of the drilled boreholes were as
  follows

Borehole No. Depth (m)
1 16.0
2 10.0
3 10.0

• laboratory test results

• ? 20 KN/m³
• qall. 3.5 kg/cm2

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• Taking the lowest compressive strength value of
  rock core specimens with test results and
  applying the percentage of 5, the strength will
  be
• b.h1 Qall 5 75 3.75 kg\cm2
• b.h2 Qall 5 70 3.5 kg\cm2
• b.h3 Qall 5 78 3.9 kg\cm2
• But considering the fact that rocks is some
  areas may be encountered in fragmented
  conditions, as well as the presence of there
  fracture rocks and marls, it is recommended to
  consider the bearing capacity value of the rock
  formations countered in the site of not more than
  3.5 kg\cm2 within the described rock layers after
  the removal of all loose fill materials over the
  rock.

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Structural design
Column loads are calculated using (sap
program), the structure subjected to the
following loads 1) Dead Load
(own weight). 2) Super imposed
dead load 350 kg/m2. 3) Live
load 500 kg/m2. Using ACI code, the ultimate
loads are calculated considering load combination
Pu 1.2Dead
1.6Live. Material characteristics used in this
project are fc 240kg/cm2 (B
300) Where
fc is the compressive strength of concrete
fy 4200 kg/cm2
Where fy is the yield strength
of steel
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Isolated Footing Design

• Manual Design steps
• Area of footing Total service loads on column
  / net soil pressure
• Determine footing dimensions B H .
• Assume depth for footing.
• Check soil pressure.
• Check wide beam shear Vc gt Vult
• Check punching shear Vcp gt Pult, punching
• Determine reinforcement steel in the two
  directions.
• Check development length .

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DIMENSIONS OF SINGLE FOOTING
Area (m2 ) L(m) B(m) Footing column
2.7 1.8 1.5 F1 c1
2.7 1.8 1.5 F2 c2
2.52 1.8 1.4 F3 c3
2.52 1.7 1.4 F4 c4
2.52 1.7 1.4 F5 c5
2.23 1.65 1.35 F6 c6
20.25 4.5 4.5 F15 C15
14.76 4.1 3.6 F16 c16
18 4.5 4 F19 c19
13.3 3.8 3.5 F20 c20
10 4 2.5 F28 c28
10 4 2.5 F31 c31
10.23 3.3 3.1 F34 c34
10.5 3.5 3 F35 c35
7.02 2.7 2.6 F36 C36
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THICKNESSES OF FOOTINGS

• Depth of footing will be controlled by wide beam
  shear (one way action) and punching shear (two
  way action).

Wide Beam Shear
Shear cracks are form at distance d from the
face of column, and extend to the compression
zone, the compression zone will be fails due to
combination of compression and shear stress.
Punching Shear
Formation of inclined cracks around the perimeter
of the concentrated load may cause failure of
footing. Max, formation of these cracks occurred
at distance d\2 from each face of he column.
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THICKNESSES OF SINGLE FOOTINGS
h(m) d(m) Footing column
0.4 0.32 F1 c1
0.4 0.3 F2 c2
0.4 0.32 F3 c3
0.4 0.32 F4 c4
0.4 0.32 F5 c5
0.4 0.32 F6 c6
1 0.9 F15 C15
1 0.9 F16 c16
1 0.9 F19 c19
1 0.9 F20 c20
1 0.9 F28 c28
1 0.9 F31 c31
0.8 0.7 F34 c34
0.8 0.7 F35 c35
0.6 0.5 F36 C36
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Steel reinforcement

• Isolated footing represented as cantilever, so
  the max moment occurs at the face of the column
• Ultimate moment at the face of the column
• (Mult) (qultln2)/2
• Mn Mu\F , where, F0.9
• Mn Rnbd2
• ? 1\m(1-( 1-2mRn\ fy ).5)
• WHERE
• ? Steel ratio
• m fy\0.85 f'c
• As ?bd

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single footing reinforcement
Reinforcement in long direction/cm Reinforcement in short direction/cm Footing
1ø16/27 1ø14/21 F1
1ø16/28 1ø14/20 F2
1ø16/28 1ø14/20 F3
1ø16/27 1ø14/21 F4
1ø14/27 1ø14/21 F5
1ø16/27 1ø14/21 F6
1ø18/12 1ø18/10 F15
1ø18/12 1ø18/12 F16
1ø18/13 1ø18/13 F19
1ø16/11 1ø16/11 F20
1ø18/10 1ø16/11 F28
1ø18/10 1ø16/11 F31
1ø16/12 1ø14/10 F34
1ø16/12 1ø14/10 F35
1ø14/12 1ø14/12 F36
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DESIGN OF COMBINED FOOTING
footing column
Fc1 C7,C8
Fc4 C23,C24
Fc5 C26,C27
Fc6 C29,C30
Fc7 C32,C33
SUMMARY OF DIMENSIONS
h(m) d(m) L(m) B(m) Footing
.8 .7 6.8 2.5 Fc1
.8 .7 11.5 2.5 Fc2
1.5 1.4 6 4.5 Fc3
1.5 1.4 7 2 Fc4
1.5 1.4 7 2 Fc5
1.5 1.4 9 3 Fc6
1.5 1.4 9 3 Fc7
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Steel Reinforcement (Flexural)
By using sap program to get the maximum negative
and positive Moment Mn Mu\F , where, F0.9 Mn
Rnbd2 As ?bd Steel reinforcement for
Fc2 The figure below show bending moment in
x-direction using SAP2000
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Mu 93.175ton.m Mn 93.175\.9
103.52ton.m Mn Rnbd2 Rn 21.1kg\cm2 ?
.0054 As 37.8cm2
Use 1 F16\12cm
The figure below show bending moment in
y-direction using SAP2000
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Steel reinforcement for Fc2

• Mu 144.822 ton.m
• Mn 144.822/ 0.9
• 160.913ton .m
• Mn Rnbd2
• Rn20.1kg\cm2
• ?.005
• As 37.5cm2
• Use 1 F16\12cm

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Steel reinforcement for Combined footing
Reinforcement in y direction Reinforcement in x direction Footing
1?16/12cm 1?16/12cm Fc 1
1?18/10cm 1?22/10cm Fc2
1?18/10cm 1?22/10cm Fc 3
1?32/10cm 1?22/10cm Fc 4
1?32/10cm 1?22/10cm Fc 5
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Mat foundation Design

• In this project the mat foundation was designed
  using Sap2000 with the following data ( fc 240
  kg \cm2,
• fy 4200 kg\cm2 )

Calculating the Thickness for mat
The thickness of mat foundation was calculated
using check for punching in the next calculation
. (the most critical for determining the
thickness for mat in the punching shear ) To
calculate the thickness , it was used the next
equation Pu .751.06(fc).5 bod
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Where Pu the load at the column bo
parameter of the bunching area d
thickness of the mat foundation
for mat foundation 1which include (col
21,22,25) Col 21 has the critical load ,Pu
377.29 ton 377.291000 .751.06(240).5(2(d50)
(2(d70))d d 80 cm
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Design of mat foundation using sap
2000 Deflection shape When we do the analysis
using sap 2000 it was found that the maximum
settlement was equal to 0.0055 m
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Reinforcement
reinforcement in x direction we take the maximum
moment at the face of columns and the maximum
between the columns. Then ,the area of
reinforcement will calculate by the Equation As
pbd 1)at the face of column Mu 123 ton
.m p 0.0054 As 0.0054 10080 As 43 cm2 use
10?25 mm/m 2)between the columns Mu 40 ton.m P
0.0016?0.0033 So use pmin 0.003 As26.4 cm2
use 10?18 mm/m
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reinforcement in y direction 1)at the face of
column Mu 75 ton.m ? 0.0032 ? 0.0033 use
? min for all the zone. As ? b d 0.0033
100 80 26.4 cm2 Use 10 ? 18 mm /
m secondary reinforcement (Negative moment) the
max. moment equals to 20 ton.m ? 0.0015 ?
0.0033 use ? min for all the zone. As ? b
d 0.0033 100 80 26.4 cm2 Use 10 ?
18 mm / m
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