an-najah national university engineering faculty civil engineering department

An-Najah National University

Engineering Faculty Civil Engineering

Department

Design of Several Foundation SystemsFor Faculty of Optics

Prepared by:Maysaa Qushou

Sama Ismail

Supervisor:Dr. Isam Jaradanah

Chapter Two presents general types of foundation system

Chapter three presents the structural system of the building that analyzed by two methods which are; tributary area and SAP2000 ver.12 program to find the loads applied on columns and walls.

Chapter four presents site investigation report including the main aspects of geotechnical prosperities

Chapter one presents the introduction of the whole project.

In Chapter five, the isolated footing is checked if it can be used or not.

while chapter six presents the design of mat foundation, including mat thickness, settlement, mat reinforcement.

Finally, chapter seven presents design of pile foundation. Single pile capacity is estimated using several methods, group of piles is found, and pile cap is designed.

The rest chapters present the design of foundations system for the proposed project.

CHAPTER TWOREVIEW OF ENGINEERING FOUNDATIONS

The lowest part of the structure generally is referred to as the foundation; its function is to transfer the load of the structure to the soil on which it is resting.

Types of FoundationsThere are two main types of foundations:•Shallow Foundations•Deep Foundations

Type of shallow foundation(isolated)

Types of deep foundation(Friction pile).

CHAPTER THREESTRUCTURAL SYSTEM

Description of the StructureThe structure that will be analyzed is the Optics Building in An-Najah University.The structure consists of seven stories building; its area is equal to 1200 m².

The main objective of this chapter is to find the loads applied on columns using two methods which are; Tributary area method and analysis using software called SAP12.

Column no.Applied load(ton)

by T.A

Loads by SAP12 (ton)

Allowable applied

loads

Ultimate applied

loads

C1 143.7 90 120

C2 56.5 60 76

C3 51.8 56.3 71.2

C4 56.5 57.2 72

C5 188.4 137.5 180.6

C6 186.5 166.8 218.4

C7 190.7 139 182.6

C8 66 56 71

C9 53 53.5 68

Loads applied on columns

CHAPTER FOURSITE INVESTIGATION REPORT

BH.

No.

Sample

No.Depth(m)

Nature

Moisture

%

Liquid

Limit

%

Plastic

Limit

%

Plasticity

Index

%

Cohesion

(from unconfined

compression test)

kg/cm² (kN/m²)

1

1 0.0 – 1.5 16

2 1.5 – 3.0 30 0.6 (60)

3 3.0 – 5.5 31

4 5.5 – 7.0 20 0.8 (80)

5 7.0 – 8.5 24 61 35 26 0.77 (77)

6 8.5 – 10.0 19 0.9 (90)

2

1 0.0 – 2.5 24 0.61 (61)

2 2.5 -5.5 31 63 34 29 0.7 (70)

3 5.5 – 7.5 19

4 7.5 – 10.0 6

Summary of Test’s Results

Cohesion(c)

(kN/m²)

Unit weight (γ)

kN/m³

Angle of

internal

friction (φ)

allowable bearing

capacity (kg/cm2)

70 17.5 0 1.7

The bearing capacity can be achieved by software called FTGBC. as shown in pages (28,29).

Consider local shear failure, then the cohesion (c) will be reduced by 2/3 and it becomes 50 kN/m². For this case the allowable bearing capacity becomes 120 kN/m².

CHAPTER FIVEDESIGN OF FOUNDATIONS

First of all we will check if Isolated footing can be designed, if we find that this method can't be used, then we will design the Mat foundations in chapter six.

In our project the space between column not enough to design single foundation and that achieved by (FTGBC) software as shown in pages(31,32).

Overlapping:Figure below demonstrates the overlapping of the stress for the two footings.

Calculations:σ1=(136)/(3.2)² = 13.28 ton/m²σ2=(115.1)/(3.5)² = 9.3 ton/m²

9.3+13.28 =18.3 ton/m² > 12 ton/m² This value is not safe . So, we can’t design Isolated footings.

CHAPTER SIXMAT FOUNDATIONS

Mat foundations are used to spread the load from a structure over a large area, normally the entire area of the structure.

To design Mat Foundations, the depth of the mat has to be found from punching shear equation manually. Then, the maximum moment in (X) and (Y) directions, area of steel and settlement are found from SAP.

To find the depth of foundation, the punching shear equation is used at edge, corner, middle. Φ Vc= (0.85)(0.34)(√fc`)(bo)(d)

The results achieved are:d = 60 cm At edge.d = 80 cm at corner.d = 40 cm at middle.

d selected = d max.= 80 cm. Then the total thickness of the mat equals:

h= d + cover + deh= 80 + 25 + 5= 110 cm

To design mat foundation in sap, spring is used as support under the foundation , so the factor of spring is calculated as the equation belowK=12*Qall=12*120=1440kn/m².

SettlementThe settlement of each column was taken from SAP12

and we find that the values is less than 1cm.

Maximum moment in (X) and (Y)directions.

The values of maximum moment in (X),(Y) directions are taken from SAP12.The figures below show the moment in (X),(Y) direction.

we use the following equations to find (As): ρ = Mu / (fc`* b * d²)As = ρ * b * d

The moment between columns gives top steel and the moment at column gives bottom steel.

for best designing the number of strip is reduced to three strips only because the moment is approximately equal and the areas of steel also convergent .

Summary in (X) direction  

Strip width(m) Moment positionMoment

(ton.m/m)ρ As(cm²/cm) Φ

8.25Between column 4.72 0.002 16 4 Φ25

At column 5.09 0.0031 25.45 6 Φ25

13.06Between column 4.77 0.0029 23.85 5Φ25

At column 4.56 0.0028 22.8 5 Φ25

16.91Between column 2.52 0.002 16 4Φ25

At column 1.32 0.002 16 4Φ25

Summary in (Y) direction

Strip width(m) Moment position Moment (ton.m/m) ρ As(cm²/cm) Φ

4.37Between column 8.39 0.0052 41.95 9 Φ 25

At column 7.76 0.0048 38.8 8 Φ25

22.89Between column 3.46 0.002 16 4 Φ25

At column 3.09 0.0022 17.3 4 Φ25

4.37Between column 7.8 0.0048 39 8 Φ25

At column 7.7 0.0048 38.5 8 Φ25

CHAPTER SEVENPILES

Piles transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity..

Design of Piles:Design of piles used in the project are done using software called Prokon using the parameters below:

Cohesion(c)

(kN/m²)

Unit weight (γ)

kN/m³

Angle of

internal

friction (φ)

50 17.5 0

Table below shows the values of allowable bearing capacity of piles by Prokon program.

Length(m)

Allowable Bearing Capacity (KN)

Pile Dia=450

mm

Pile Dia=600

mm

Pile Dia=700

mm

Pile Dia=800

mm

Pile Dia=1000

mm

6 97 139 170 204 279

8 136 191 231 294 366

10 180 250 300 353 464

12 229 316 377 440 573

14 282 387 460 535 670

16 340 463 549 636 819

Allowable bearing capacity of pile versus pile length and diameter.

Type No. Pile length Pile diameter Pile Capacity

1 10 m 600 mm 250 kN (25.5 ton)

2 12 m 700 mm 377 kN (38.4 ton)

Two types of piles are selected in the design of pile foundation in this project, which are shown in the following table:

Types of piles

Table below shows the allowable applied load and the No. of piles with cap’s dimensions that each group of column has.

No. of piles and the dimensions of caps

Column No.Allowable applied

loads(ton)Pile diameter and Length No. of piles

Dimensions

of caps (m)

C1 90 700 mm, 12 m 2 3.1*1

C2 60 700 mm, 12 m 2 3.1*1

C3 56.3 600 mm , 10 m2 2.8*1

C4 57.2 600 mm , 10 m2 2.8*1

C5 137.5 700 mm, 12 m 4 3.1*3.1

C6 166.8 700 mm, 12 m 4 3.1*3.1

C7 139 700 mm, 12 m 4 3.1*3.1

C8 56 600 mm , 10 m 2 2.8*1

C9 53.5 600 mm , 10 m 2 2.8*1

Area of steel neededThe equations below is used to determine the area of steel :Mu=Pu*e

Mn=BM/ɸ

Where: Ø= 0.9

Rn=MN/BD²

m= Fy/(Fc*0.85)

Vu =(Pu*no.of piles in each side of col.)/total no. of piles in the cap

d is assumed and checked if ok or not by Punching shear and Wide beam shear.

So , As= ρ*B*d

ρ=1/m * ( 1- √(1((2*Rn*m)/Fy)) )

Col. #

Col. Dim. (cm)

d (cm)

Cap Dim. (cm)

Pu (ton)

e(cm)

Mu (ton.m)

Mn (ton.m)

Rn (Kg/cm²)

ρAs

(cm²)

C1 30*30 90 310*100 120 90 108 120 14.8 0.0036 33

C2 40*60 55 310*100 76 85 64.6 71.7 23.7 0.006 33

C3 40*60 55 280*100 71.2 70 49.84 55.4 18.3 0.0045 25

C4 40*60 55 280*100 72 70 50.4 56 18.5 0.0046 25.4

C5 40*40 45 310*310 180.6 85 153.5 170.6 27 0.007 97.7

C6 40*40 55 310*310 218.4 85 185.6 206.3 22 0.0055 94.5

C7 40*40 55 310*310 182.6 85 155.2 172.5 18.4 0.0046 78.2

C8 40*40 55 280*100 71 70 49.7 55.2 18.3 0.0046 25

C9 40*40 55 280*100 68 70 47.6 53 17.5 0.0044 24

The areas of steel that calculated for the rest caps are presented in the following table: