Calculation Note Final

1

Kafr El Sheikh University

Faculty of Engineering

Civil Engineering Department

Suez-Canal

Cable-Stayed Bridge Project

(The Graduation Project)

Prepared By /

Mohamed Ahmed Elfeky

Mohammed Abdelkawy

Ahmed Bahgat Zamil

4th Year Civil

2

The Cable-Stayed Bridge

Basics

The position of cable-stayed bridges within all bridge systems their spans

range between continuous girders and arch bridges with shorter spans at

one end, and suspension bridges with longer spans at the other. The

economic main span range of cable-stayed bridges thus lies between

100m with one tower and 1100m with two towers.

A typical cable stayed bridge is a deck with one or two pylons erected

above the piers in the middle of the span. The cables are attached

diagonally to the girder to provide additional supports. Large amounts

of compression forces are transferred from the deck to the cables to the

pylons and into the foundation.

Cable stayed-bridges have a low center of gravity, which makes them

efficient in resisting earthquakes. Cables are extremely well suited for

axial tension, however are weak against compression and bending forces.

As a result, long span cable stayed bridges, though strong under normal

traffic loads, are vulnerable to the forces of winds. Special measures are

taken to assure that the bridge does not vibrate or sway under heavy

winds.

Because the only part of the structure that extends above the road is the

towers and cables, cable stayed bridges have a simple and elegant look.

3

Advantages of cable-stayed bridges:

First of all the bending moments are greatly reduced by the load transfer

of the stay cables, By installing the stay cables with their predetermined

precise lengths the support conditions for a beam rigidly supported at the

cable anchor points can be achieved and thus the moments from

permanent loads are minimized, Even for live loads the bending moments

of the beam elastically supported by the stay cables remain small.

Large compression forces in the beam are caused by the horizontal

components of the inclined stay cables. The normal forces in the main

and side span equal one another so that only uplift forces have to be

anchored in the abutments which act as hold-down piers.

A second important advantage of cable-stayed bridges is their ease of

construction;

- Arch bridges with large spans are not stable during erection until

The arch is closed and the horizontal support forces are anchored.

- Self-anchored suspension bridges, which may be required when

Their horizontal cable component cannot economically be anchored

Due to bad soil conditions, need temporary supports of their beams

until the main cables are installed.

4

- In cable-stayed bridges, however, the same flow of forces is

Present during free-cantilever construction stages as after completion.

This is true for free cantilevering to both sides of the tower

As well as for free cantilevering the main span only.

The Main Components OF Cable Stayed

Bridge:

1-Deck: The deck or road bed is the roadway surface of a cable-stayed bridge.

The deck can be made of different materials such as steel, concrete or

composite steel-concrete. The choice of material for the bridge deck

determines the overall cost of the construction of cable stayed bridges.

The weight of the deck has significant impact on the required stay cables,

pylons, and foundation.

6

Pylon

7

2-Pylon: Pylons of cable stayed bridges are aimed to support the weight and live

load acting on the structure. There are several different shapes of pylons

for cable stayed bridges such as Trapezoidal pylon, Twin pylon, A-frame

pylon, and Single pylon. They are chosen based on the structure of the

cable stayed bridge (for different cable arrangements), aesthetics, length,

and other environmental parameters. The first cable-stayed bridges used steel towers. Since towers are mainly

loaded by compression, concrete towers are more economical and,

therefore, mainly used today. Only if extremely bad foundation

conditions would require very long piles, are the lighter steel towers used

today.

8

3-Cables: Cables are one of the main parts of a cable-stayed bridge. They transfer

the dead weight of the deck to the pylons. These cables are usually post-

tensioned based on the weight of the deck. The cables post-tensioned

forces are selected in a way to minimize both the vertical deflection of the

deck and lateral deflection of the pylons. There are four major types of

stay cables including, parallel-bar, parallel-wire, standard, and locked-

coil cables. The choice of these cables depends mainly on the mechanical

Properties, structural properties and economic criteria.

9

1- Locked coil ropes: Traditionally used in Germany, completely

shop fabricated, permit construction by geometry.

Advantages: good corrosion protection, simple maintenance

Disadvantages: reduced stiffness, subject to creep, reduced tensile

strength and fatigue strength. Locked coil ropes consist of internal round wires with a diameter of

5 mm and outer layers of Z-shaped wires with a depth of 6 – 7 mm,

Fig. 3.2. Their modern corrosion protection comprises galvanizing of all

wires, filling the interstices with a corrosion inhibitor and painting the

outside in several layers.

The different wire layers rotate in opposite directions in order to achieve

twist-free ropes, Fig. 3.3.

10

When stressing the cables, the Z-shaped outer wires are pressed against

one another by lateral contraction and which ‘locks’ the rope surface

against intrusion of water, hence the name ‘locked coil ropes’.

11

2- Parallel wire cables: Developed by LAP in the 1960s from

BBR post-tensioning system in order to overcome the disadvantages of

Locked coil ropes, almost exclusively used in Germany since then, also

completely shop-fabricated.

Advantages: high stiffness, no creep, high tensile and fatigue strength

with Hiam-anchorage

Disadvantage: complex corrosion protection with several components

Parallel wire cables comprise a bundle of straight wires with 7 mm or 1⁄4

inch diameter which are anchored with button heads in a retainer plate.

In order to further improve the fatigue strength, the so-called ‘HiAm’

anchorage was developed and investigated in many tests.

The basic design idea is to anchor the individual wires gradually by

lateral pressure exerted by small steel balls into which the wires are

broomed-out inside a conical anchor head.

13

3- Parallel strand cables: Developed from strand tendons in

order to exploit higher tensile strength and better availability of strands

Advantages: cost-effective, fabrication on site from components,

exchange of individual strands

Disadvantage: slightly reduced stiffness.

16

Main Types of Cable Stayed Bridges:

18

Bridge Layout

1) Bridge Structural Type: Concrete Box Girder

Cable-Stayed Bridge

2) Span Arrangement: 165+400+165=730m

3) Stay Cable Arrangement: Semi Fan

4) Stay Cable: Strand Cables

5) Pylon Type: Reinforced Concrete H-Shaped Column

6) Pylon Height: 150m

7) Navigation Clearances: 70m Above H.H.W.L

8) Bridge Width: 20m

19

Bridge Components

Cable-Stayed bridges have 3 main components:-

1) Pylon

2) Deck

3) Cables

3D Model

20

The Pylon

The Pylon is the main support of cable-stayed bridges.

Cables link the deck to the pylon, so it can carry the deck

safely.

Our pylon is a Reinforced Concrete H-Shaped Column.

The section of the pylon is a nonprismatic section

Pylon Bottom Pylon Top

21

The Deck

The Deck View

The Deck Properties:-

The Deck Width = 20.00 meter

(Consists of 4 lanes - 2 lanes in each direction , 2

sidewalks of width equals 2.0 m , and an island of

width equals 2.0 meters)

t1 = t2 = t3 = t4 = 0.30 m t5 = t6 = 0.25m

L1 = L2 = 2.00 m

The Depth = 3.00 m

22

Material Properties for Pylon and Deck:

concrete has a specified compressive strength equals

400 kg/cm^2, Considering Creep and Shrinkage.

23

Cables

In this bridge we have 16 cables in each side of the

pylon

The distance between cables in the deck plan equals

to 10.00 meters In the Side Spans and Equal To

12 meters Between the Pylons

The distance between them at its links to the pylon

equals to 2.00 meters

Material Properties:

Fu = 17.7 T/Cm^2

Fy= .89* 17.7 = 15.7 T/Cm^2

E = 1950 T/Cm^2

Diameter = 15.7 mm

24

Modeling Steps

(Using CSI Bridge Program)

1) Drawing the layout line of the bridge.

The layout has 2 stations the 1st at 0.0 and the 2

nd at

730.00.

2) Defining the deck sec. which is box girder has 3

vents.

3) Defining Lanes.

4) Defining and drawing the pylon.

5) Defining and drawing the rigid links to link the

deck sec. to cables as one unit.

6) Defining springs.

7) Solving the model to get the deformation due to

dead load.

8) Defining the cables (Diameter & Pretension

Force) which achieve deformation equals to zero.

9) Defining the design vehicle and vehicle class.

10) Defining All Cases Of Moving Load.

11) Solving due to moving load and getting

deformation.

25

12) Defining the Earthquake loads Using Static

Analysis (Seismic Coefficient Method) and Safety

Was Checked by Dynamic Analysis (Time History

Method).

15) Solving the model due to earthquake forces.

16) Defining the wind loads.

17) Solving.

18) Defining load combinations.

19) Design the bridge.

Philosophy of Analysis:

1-Find the value of cable tension that will give

optimum deck profile for final model.

2- Stage construction analysis to find cable force

during erection.

3- Final checks with seismic, Wind and other effects

26

The Program Outputs:

Deformation due to Dead Load only (Without Cables)

Joints Labels

These joints are at the center of the deck.

28

From the table:

The max deflection is at p54 and p56 which are at

the mid span, and equals to 54.41 m.

29

We will use 3 groups of cables

The 1st one consists of 5 cables (the nearest cables to

the pylon)

This group has cables of diameter equals to 7.00

cm, and a tension force of 340 ton of its end I

which linked to the pylon.

The Force in cables is put in a load pattern called

Target.

After Using Cables With Pretension Force:

30

The 2nd group consists of the next 5 cables.




The 3rd group consists of the next 6 cables.




31

Deformed Shape:

Almost no deformation …

The output values are due to the combination

between Target and Dead Load.

33

The uplift at P34 equals to 3 cm, and the max

Settlement equals to 1.5 cm at P71.

34

The Pylon Sway due to Dead Load:

The Max Sway from D.L. equals to17.6 cm.

The Moment Diagram:

Max Moment = 7272 t.m

35

The Shear Force Diagram:

Max Shear = 840 ton.

The Normal Force Diagram:

Max axil compression force in deck =12064 ton

Reaction for pylon Column = 16574 ton

36

Moving Loads:

The Bridge consists of 4 lanes, 2 lanes in each

direction, and 2 sidewalks of 2.00 m width in each

one and central median 2m Width.

The lane width equals to 3.50 meters.

37

Moving Load Model (1):

Consists Of concentrated and distributed load.

Truck 60ton.

Truck40ton.

38

Truck 20ton.

Uniform 0.25t/m^2 for The rest of road width

Uniform 0.5t/m^2 for Pavements and Median

40

The max deflection equals to 29 cm

41

Bending Moment Diagram:

Max Moment = 3956 t.m

Shear Force Diagram:

Max Shear = 243 ton

42

Normal Force Diagram

Max Torsion = 1882 t.m

Moving Load Model (2):

consists of uniform 0.5t/m^2 for bridge width

43

the max deflection equals to 28.9 cm

allowable Deflection (50-80) cm Safe

44

Load Case for torsion

(2 lanes occupy other 2lanes are empty)

Max Torsion Moment = 2606 t.m

45

Earthquake Analysis

Dynamic Time History linear Analysis

1) Define Mass Source:

46

2) Define Time History Function:

(time &acceleration)

We Will Use (ELCENTRO) General EQ

in X&Y Direction

47

3) Define Time History Load Case:

- Damping Ratio: Take (2%)

- Response Modification Factor (R): Take = 3

48

If we Want to increase the damping ratio

we can use cable anchorage with Hydraulic Damper

For great values up to 5%.

This is reducing the response of the super structure.

49

- Scale Factor: I*g/R= (1.3*9.81)/ (3) =4.25

51

Max Lateral Displacement = 28.7 cm

52

Normal Force Diagram

53

Shear Force Diagram

54

Bending Moment Diagram

55

Seismic Analysis Using (Simplified Response Spectrum)

>> (Seismic Coefficient Method) <<

57

Max Lateral Displacement = 29.6 cm

58


59

Shear Force Diagram

60

Base Reactions

61

Wind Loads

Wind load which affect on the deck of the bridge

and on the trucks can be calculated from the

EGYPTIAN code of loads as following:

62

Wind Load on Deck (With Live Load)

Wind load (deck) = 0.15 * 6 = 0.9 ton /m.

The wind applied in Y – Direction.

64


65

Load Combinations

1) Characteristic Load Combinations

According To Egyptian Code:

1.35 Dead+1.35 Live (1)

1.35 Dead+1.35 Live (2)

1.35 Dead+1.35 Live (1) +0.9 Winds

1 Dead+0.2 Live (1) +EQ

1 Dead+0.2 Live (2) +EQ

66

Final Design Design of cable: Subjected to Tension with

Small Compression Values:

67

Design of pylon: pylons designed as

Columns subjected to Axial Force and Biaxial

Moments.

Max Straining Action:

p m3 m2

23817.09 -3748 -5006.61

17244.32 -2914.12 -35635.8

17913.68 9806.453 -12637

17358.85 3167.38 31823.26

68

Design by SCI COLUMN Program:

Using 254 bar ᶲ 22

Total area Steel=966 Cm^2 Steel ratio = 0.4%

69

Design of the Deck:

Max Straining Action:

Max Compression= 18171 ton

Max positive Mx=9972.35 t.m

Max negative Mx= -9605 t.m

Max Positive My= 26560 t.m

Max Negative My= 27280 t.m

Max Torsion = 2845 t.m

Max Shear = 1272 ton

70

Flexure Design

For Exterior Girder (right, left)

Using upper and lower

R.F.T = 50 ᶲ 25

(Upper & Lower)

Achieve Moment of

Resistance = 2512t.m

71

For Exterior Girder (right, left)

Using upper and lower

R.F.T = 60 ᶲ 25

Achieve Moment of Resistance =

3330t.m

72

Design of Sec Using CSI COLUMN as Column:

73

Comparison for Better Results:

1- We can use prestressed concrete to achieve the

tensile stresses and get Small effective cross section

or using Steel deck.

2- We can do camber for Pylon and the deck to

prevent high deflections for the deck And lateral

Displacements For the pylon

3- high damping rubber bearings (HRB) were used

as seismic isolators (supports) for the steel girder,

With allowable movable length (seismic) = ± 450

mm.

4- To limit the horizontal movements, lateral rubber

bearings were installed between the bridge deck and

the tower with a gap of 10 mm.

Calculation Note Final

Documents

Transcript of Calculation Note Final