AbstractAbstract

*Our project is about ( Foundation Design of Al-Maslamani Mall) which is located in the village of Beit Eba – Nablus governorate.

*The total plan area of this mall is about 3500 m2

*The number of stories is 6; 4 stories above the ground surface & 2 stories are below the ground surface.

Literature ReviewLiterature Review Site Investigation is the first important step in any engineering

work ; to determine type & depth of foundations , to evaluate bearing capacity , to identify construction methods & for many things…

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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Isolated footings Piles

Combined Foundations

Mat

  Isolated FootingsIsolated 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 .

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.

Mat or Raft 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.

Combined Foundations

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 .

Strap or Cantilever Footings

Pile FoundationsPile 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.

Classification of the pilesClassification of the piles

According to load transmission & functional behavior :1) End / Point bearing piles2) Friction piles3) Compaction piles

According to type of material:1) Steel piles 2) Timber piles3) Concrete piles 4) Composite piles

According to effect on the soil:1) Driven piles2) Bored piles

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.

Any structure built on soil is subject to settlement. Some settlement is inevitable, & depending on the situation, some settlements are tolerable.

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.

Bearing Capacity & Settlement

Geotechnical InvestigationThe studied area is approximately flat with slight difference in the three existing elevations. The general soil formation within the depths of the borings consists mostly of wadi deposits of boulders & silty clay followed by successive layers of hard boulders mixed with very little filling silty clay. The whole site is covered by grass.

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

= 20 KN/m³ w = 7.6 % (avg.) C = 0 KN/m² (average) LL = 44.5 % Ø = 25 º PI = 25 qall. = 3.0 kg/cm2 G = 2.73 a-Coefficient of active earth pressure: KA = 0.405 b- Coefficient of passive earth pressure: KP = 2.464 c- Coefficient of pressure at rest: Ko = 0.577

The depths of the drilled boreholes were as follows:The depths of the drilled boreholes were as follows:

Borehole No. Location Depth (m)

1 South-west 7.0

2 East 7.0

3 West 6.0

4 North 10.0

Summary of lab. test results:

After doing check on the bearing capacity value using FOUND

software by using Terzaqi and Meyerhoff formulas, the value

was ranging between 3.2 and 4.3 Kg/ cm2 respectively, SO we

decided to use a value of 3.5 Kg/ cm2 in our project.

Column # Footing # Ultimate Load (ton)

Service Load (ton)

C21 ,C28 F1 60 44.5

C8 ,C9 F2 120 89.0

C3 ,C38 F3 183 135.7

C1,C2,C7,C23,C30,C32,C43

F4 243 180.3

C10,C15,C31,C37,C39,C4,C16

F5 347 257.4

C5,C6,C22,C29,C33, C41,C42,C24,C36,C40

F6 388 287.8

C11,C12,C13,C14,C17,C34,C35

F7 522 387.2

C18,C19,C20,C25,C26,C27

F8 579 429.5

Load Calculations

Manual Design steps:

1) Area of footing = Total service loads on column / net soil pressure

2) Determine footing dimensions B & H .

3) Assume depth for footing.

4) Check soil pressure.

5) Check wide beam shear : ΦVc > Vult

6) Check punching shear : ΦVcp > Pult, punching

7) Determine reinforcement steel in the two directions.

8) Check development length .

9) Check load transfer from column to footing .

Then, we compare manual design with SAP design in footings F4 & F8 .

Isolated Footing Design

The solution of SAP is always smaller than manual one, since SAP uses Finite Element Method.

There is no need to calculate the settlement of the isolated footings; since the soil is gravelly soil , & has a qall. of 3.5 kg/cm2 .

The final results of isolated footings design are in the next table :

Column # F #

Columns Dimension( m)

H (m)

B (m)

Depth (m)

As , H

(mm2)

As , B

(mm2)

C21 ,C28 F1 D= 0.5m 1.1 1.1 0.4 816 816C8 ,C9 F2 0.5*0.2 1.6 1.6 0.5 1548 1548C3 ,C38 F3 C3 : 0.7*0.4

C38 : D = 0.8 m2 2 0.45 1710 1710

C1,C2,C7,C23, C30,C32,C43 F4

C1, C2, C30 : 1.1*0.4C7: 0.65*0.3C23 : 0.75*0.75C32 : 0.8*0.8C43 : 0.6*0.3

2.5 2.5 0.52 2614 2614

C10,C15,C31,C37,C39,C4, C16

F5

C10 : 0.75*0.75C15 , C37 : 0.6*0.3C31 : 1.1*0.4C39 : D=0.8mC4 : 0.4*0.65C16 : 0.75*0.75

2.85 2.85 0.90 5330 5330

C5,C6,C22,C29, C33,C41,C42, C24,C36,C40

F6

C5,C6,C40,C41,C42 : 0.8 * 0.65C22 , C29 : 0.6*0.3C24 : 0.75*0.75C33 : 1.1*0.4C36 : D=0.8 m

3 3 0.80 4930 4930

C11,C12,C13, C14,C17,C34, C35

F7

C11,C12,C13,C14,C35: D= 0.8 mC17 , C34 : 0.75*0.75 3.5 3.5 0.90 6540 6540

C18,C19,C20, C25,C26,C27

F8 C18,C19,C20,C26,C27: D=0.8 mC25 : 0.8*0.8

3.8 3.8 0.95 7530 7530

Wall Stair FootingWall Stair Footing

Dimensions and Reinforcement Dimensions and Reinforcement Details of Wall Stair FootingDetails of Wall Stair Footing

Depth of wall footing = 60 cm.Width of wall = 20 cm.Width of footing (B) = 2 m.

Reinforcement:6 φ16 / m in short direction14 φ16 in long direction

Elevator Wall FootingElevator Wall Footing

Dimensions and Reinforcement Dimensions and Reinforcement Details of Elevator Wall FootingDetails of Elevator Wall Footing

Depth = 33cm, h=40cm

4 φ16 / m

For positive moment & negative moment

In both directions.

Reinforcement details for elevator wall :

Pile FoundationPile Foundation

Design of pile foundationDesign of pile foundation

1-Estimating pile capacity

The ultimate carrying capacity is equal to the sum of the ultimate resistance of the base of the pile and the ultimate skin friction over the embedded shaft length of the pile, this expressed by :

Qu = Qp + Qs

2-Determination of the point bearing capacity

For piles in rocky sand soil as in our case , the point bearing capacity may be estimated as :QP = Ap q' Nq* ≤ QlimitWhere:Ap : Area of the pile tip.

q’ : effective stress at pile tip.Nq*: Factor depends on soil friction angle

Qlimit =(0.5 Pa Nq* tan Ø ) Ap

3-Determination of skin resistance

It can be calculated by using the following formula:

QS =∑ {P*∆L*f }

Where:∆L : Length of the pileP : Perimeter of the pilef : Frictional factor

The following table presents the dimensions The following table presents the dimensions of piles and their capacities in (KN).of piles and their capacities in (KN).

length)m(

D(m) 8 10 12 14 15 16 18

0.5 122 164 216 278 312 349 430

0.6 157 208 271 345 386 430 526

0.7 196 256 329 415 463 514 627

0.8 239 307 390 489 544 602 731

0.9 285 362 455 566 628 694 839

1 335 420 524 647 716 789 951

Summary of piles sizes, number of piles needed, cap dimensionsSummary of piles sizes, number of piles needed, cap dimensions::

Column# Service Load)KN(

Pile size )L,D()m,m(

#of pilesCap

dimension)m(

21+28) F1( 445 )8 , 0.5( 4 2.2×2.2

8+9) F2( 890 )14 , 0.5( 4 2.2×2.2

3+38) F3( 1357 )16 , 0.5( 4 2.2×2.2

1+2+7+23+30+32 +43) F4(

1803 )15 , 0.7( 4 2.85×2.85

10+15+31+37+39 +4+16) F5(

2574 )15 , 0.7( 6 4.6×2.85

5+6+22+29+33+41 +42+24+36+40

) F6(

2878 )14 , 0.8( 6 5.2×3.2

11+12+13+14+17 +34+35) F7(

3872 )14 , 0.8( 8 7.2×3.2

18+19+20+25+26 +27) F8(

4295 )15 , 0.8( 8 7.2×3.2

The structural pile design depends on the nature of soil, which is either stiff or weak, the pile is to be designed as short column if the soil is stiff , and designed as along column if the soil is weak.

The minimum area of steel is 0.5% of the gross area of the pile, also the ties are used starting with 5 cm spacing and ending by 30 cm spacing .the concrete cover must be not less than 7.5 cm.

Asmin=0.005Ag

 

Efficiency of pile group Efficiency of pile group

The efficiency of the load-bearing capacity of a group pile may be defined as:

M= Qg(u ) / ∑Qu

Where:

Qg(u)= ultimate load bearing capacity of the group pile.

Qu= ultimate load-bearing capacity of each pile without the group effect Using simplified analysis to obtain the group efficiency as shown in the following

formula:

ζ = (2(m+n-2) + 4D) / (p×m×n)

Where:

m: # of piles in the direction of Lg.

n:# of piles in the direction of Bg.

d: Spacing between piles centers.

D: Diameter of the pile

P: Perimeter of pile cross section

Design of a pile capDesign of a pile cap:: The minimum distance between two piles is 3D. Pile caps should extend at least 15 cm beyond the outside

face of exterior face of exterior piles. The minimum thickness of pile cap above pile heads is 30

cm. The cover in pile caps commonly ranges between 20 & 25

cm .

Design Steps:

1) Assume depth (d)

2) Check Punching shear : ΦVcp > Vult, punching

3) Check wide beam shear : ΦVc > Vult

4) Calculate area of steel needed

5) Check ρmin. < ρ < ρmax.

Retaining Wall Design:Retaining Wall Design:

The retaining wall is designed by PROKON Program :

Conclusions:Conclusions:1 (From soil report, we note that PI is 25 and cohesion is zero and this

can be explained by the following:

We have soil contains some clay between gravels, and when we take a sample of this soil to be tested for atterberg limits to determine PI,we use sieve #40 and we take the passing which are clay particles and in turn this leads to increase the magnitude of plasticity index.

Cohesion is zero since the soil sample is almost gravel .

2 (After designing the two alternative choices (single footings and piles system) & surveying the quantities for concrete only, we find that it is more practical, realistic and economical to use single footings

3 (there is no need to make settlement calculations for footings and piles ,since we have a gravely soil with B.C of 3.5 kg/cm2(the

settlements in our situation are tolerable, so we can ignore them)..