- 156 -

B.3.5.1.2 Expansion

Without any longitudinal restraint, the maximum deck movement will be in the range of ±1.9m for the

load combination of L+T and L+W as shown in Table B.3.5.1-1. Since this movement is extremely

large, very frequent maintenances and repair works on the bearing and expansion joint are foreseen.

The movements are limited to ±1.0m by introducing hydraulic buffer system between the deck and

the anchorages and thereby expansion joints with the capacity up to ±1.1m are installed at both ends

of the deck. Deck movement ranges with hydraulic buffers are shown in Table B.3.5.1-2. The

hydraulic buffer is designed in order to reduce fast movements from traffics passing, braking,

dynamic wind and earthquake and to physically block movements exceeding the limit.

Table B.3.5.1-1 Deck movement ranges without any longitudinal restraints (unit: m)

Load Cases North anchorage South anchorage

Openings Closings Closings Openings

Live(L) -1.46 1.37 -1.37 1.46

Temperature(T) -0.42 0.46 -0.46 0.42

Settlement (SD) -0.07 0.07 -0.07 0.07

Error (E0) -0.01 0.01 -0.01 0.01

Wind(W) -0.33 0.33 -0.33 0.33

Earthquake(EQ) -0.66 0.66 -0.66 0.66

L+T -1.88 1.83 -1.83 1.88

L+W -1.79 1.70 -1.70 1.79

Table B.3.5.1-2 Deck movement ranges with hydraulic buffers (unit: m)

Load Cases North anchorage South anchorage

Openings Closings Closings Openings

Live(L) -0.64 0.57 -0.57 0.64

Temperature(T) -0.42 0.46 -0.46 0.42

Wind(W) -0.33 0.33 -0.33 0.33

L+T -1.06 1.03 -1.03 1.06

L+W -0.97 0.90 -0.90 0.97

B.3.5.1.3 Navigation clearance check

The main navigational clearance of 1000m x 64m is provided as per RFP under reference loading

condition. The loading conditions for the check of navigational clearance are found as in Design Basis

of Great Belt East Bridge. For the Izmit Bay Bridge, it is assured the navigational clearance can be

maintained with a minimum clearance height of 1.2m between deck soffit and navigation clearance

for the load combination of 1.0G + 1.0T + 0.5L.

- 157 -

Vertical deflections

The vertical deflections under service loading conditions are tabulated as follows.

Locations Live Wind Temperature Earthquake Error

At side span(1/2) -6.92m -0.64m -0.21m -1.48m -0.08m

At tower -1.50m -0.25m -0.11m -0.52m -0.04m

At main span (1/4) -9.76m -1.50m -0.99m -1.08m -0.42m

At main span (1/2) -10.50m -1.63m -1.34m -0.43m -0.58m

Navigational clearance

Locations

Proposed

elevation

(A)

Girder

depth

(B)

Girder

deflection

(C)

Obtain

clearance

(D) =(A)-(B)-(C)

Navigation

clearance

(E)

Allowance

(D)-(E)

Point A 74.703m 4.5m 5.050m 65.153m 64m 1.2m

Point B 79.090m 4.5m 7.380m 67.210m 64m 3.2m

B.3.5.2 Orthotropic Steel Bridge Deck

B.3.5.2.1 General

Design of the bridge deck is in accordance with EN 1993 and based upon verification of ultimate limit

state strength by using partial factor method.

Partial factors for steel materials are to be taken into account in accordance with BS EN 1993-2:2006

Resistance of Partial factors Value Remark

Cross sections γM0 1.00

Members γM1 1.10

B.3.5.2.2 Cross sections

A streamlined box cross section having rounded fairing has a total width of 36.7m. The deck plate is

14mm thick, which is a minimum requirement for the surfacing layer of 70mm, according to EC3.

The 14mm of deck plate thickness and 12mm of sidewalk plate thickness are applied along the entire

- 158 -

length of the bridge deck. For the bottom and web plates, a minimum thickness of 8mm is adopted at

normal cross section and increased up to 20mm in the vicinity of the towers. The closed stiffeners

with trapezoidal profiles are used. 300mm × 275mm × 6(8) troughs for deck plate and 450mm

× 225mm × 6(8) troughs are adopted at both 600mm centre at deck and 900mm centre at bottom

flange, respectively. The bridge deck cross sections are classified into 2 types and its material

characteristics are tabulated below.

An open truss type diaphragm is adopted at 4.0m spacing in longitudinal direction, which is more

economical than full plate type bulkhead. The spacing of 4.0m is a well known support condition for

the orthotropic deck.

It is assumed that all cross sections are classified to Class 4 in which local buckling will occur prior to

the attainment of yield stress. The effects of local buckling and shear lag have been considered by

effective width method which reduces resistance instead of the yield strength.

Cross section (Typical)

Material properties Unit TYPE 1 TYPE 2 Remarks

Steel grade - HSB 500 SM520 HSB 600 SM570

Yield strength(fy) MPa 380 360 450 450

Ultimate tensile strength(fu) MPa 500 520 600 570

Modulus of elasticity(E) MPa 210,000 210,000 210,000 210,000

- 159 -

B.3.5.2.3 Resultant forces for ULS combination

The resultant design force envelopes for the bridge deck from global analysis are plotted as shown

below.

Axial forces envelopes

The axial force envelopes for the cases of maximum and minimum bending moments are shown

below.

Vertical bending moment envelope

Horizontal bending moment envelope

- 160 -

Shear forces envelope

B.3.5.2.4 Bridge Deck

Fiber stress points

Resistance of cross section

(1) Resistance to flexural bending stresses

The design value of a loading effect in each cross section does not exceed the corresponding design

resistance and if several loading effects act simultaneously the combined effect does not exceed the

resistance for that combination.

Members which are subjected to combined bending and axial force satisfy:

1/// 0min..

.

0min..

.

0

≤+

++

+⋅ Myzeff

NzEdEdz

Myyeff

NyEdEdy

Myeff

ED

fW

eNM

fW

eNM

fA

N

γγγ

where, Aeff is the effective area of the cross section when subjected to uniform compression

Weff.min is the effective section modulus (corresponding to the fibre with the maximum

elastic stress) of the cross section when subjected only to moment about the relevant axis

eN is the shift of the relevant centroidal axis when the cross section is subjected to

compression only

- 161 -

(2) Resistance to flexural shear stresses

For unstiffened or stiffened webs the design resistance for shear is taken as:

Ml

hfVVV

wtyw

RdbfRdbwRDb⋅

⋅⋅≤+=

γ

η

3...

where, the contribution from the web is given by :

Ml

wyww

Rdbw

thfV

γ

χ

3.

⋅⋅⋅=

and the contribution from the flanges Vbf,Rd is not considered in this calculation.

The resistance for shear satisfies the following criteria.

0.1.

3 ≤=Rdb

Ed

V

Vη

(3) Interaction between shear force, bending moment and axial force

Provided that η3 does not exceed 0.5, the design resistance to bending moment and axial force need

not to be reduced to allow for the shear force. If η3 is more than 0.5, the combined effects of bending

and shear in the web of an I or box girder satisfy:

( )Rdpl

Rdf

Rdpl

Rdf

M

Mfor

M

M

.

.

1

2

3

.

.

1 0.1121 ≥≤−

−+ ηηη

(4) Summary for bending and shear check

For all elements, the capacity of cross sections along the length of the steel girders has been verified

to be satisfactory. The verification and limit criteria are plotted along the length of the girder as shown

below.

① Bending check (Check Point 01, 02)

- 162 -

② Bending check (Check Point 03,04)

③ Bending check (Check Point 05)

④ Bending check (Check Point 06)

- 163 -

⑤ Shear check

Provided that the design value of the shear force VEd does not exceed 50% of the design plastic shear

resistance Vb,Rd, no reduction of the resistance for bending and axial force need be made.

B.3.5.3 Cable Structures

B.3.5.3.1 Main cable

The main cable is formed from high strength galvanized steel wires with a minimum tensile strength

of 1960MPa, laid parallel and erected by PPWS method. Each cable has a configuration of 154

strands whereof a strand comprises 127 wires of diameter 5.4mm. 19558 in total wires correspond to

a cable area of 0.44792m2. The air void ratio is assumed to be in the order of 20% after cable

compaction and 18% for banded cables.

Main cable cross section before compaction Main cable cross section after compaction

Material Properties Unit Wires Remarks

Grade - KS D 3509 PWR Wrapping wire S-type 3mm

Diameter mm 5.4

Yield strength (fy) MPa 1,530

Ultimate tensile strength (fu) MPa 1,960

Modulus of elasticity (E) MPa 210,000

Yield tensile force MN 685

Ultimate breaking load MN 788

- 164 -

Verification of resistance

The main cables have been designed for both ultimate limit state (ULS) and service limit state (SLS)

in accordance with EN 1993-1-11:2006. For ultimate limit state, applied axial forces will not exceed

the design tensile resistance. For serviceability limit state, stress and strain levels in the component

will not exceed the limiting values.

(1) ULS verification

The resistances of cables have been verified as follows

1≤Rd

Ed

F

F,

=R

k

R

ukRd

FFF

γγ,

5.1min

(2) SLS verification

The stress level is limited to 45% of tensile strength: FRD = 0.45 Fuk

Limit state Splay saddle Side span Main span Center node

ULS

ULS 482 528 519 478

FRD_ULS 585 585 585 585

Utilization ratio 0.82 0.90 0.89 0.82

Check O.K O.K O.K O.K

SLS

SLS 356 390 384 353

FRD_SLS 395 395 395 395

Utilization ratio 0.90 0.99 0.97 0.89

Check O.K O.K O.K O.K

As shown in the above table, serviceability check takes precedence over ULS verification. For

serviceability limit state, the maximum cable tensile force of 395MN occurs at side span in the

vicinity of the main tower. The maximum utilization ratio reaches 0.99, which corresponds to safety

factor of 2.2.

B.3.5.3.2 Hangers

A hanger is very slender and high strength element that carries the loads from the suspended bridge

deck. Because of their small cross section, the bridge might be exposed to vulnerability with regard to

accidental damage. In particular, the risk of progressive collapse will be thoroughly assessed and

necessary means to mitigate the risk will be taken. Since this bridge sustains relatively high traffic

loads, double hanger system will be more advantageous than single hanger system in case of hanger

loss, and therefore the double hanger system has been adopted.

- 165 -

Hanger cross section

Four different sizes of hanger in the following table are used.

Items TYPE-H1 TYPE-H2 TYPE-H3 TYPE-H4

Cross sections

No. of wires Φ5.0mm-151 Φ5.0mm-211 Φ5.0mm-223 Φ5.0mm-367

Areas 2,965mm2 4,143mm

2 4,379mm

2 7,206mm

2

Grades KS D 3509 KS D 3509 KS D 3509 KS D 3509

Tensile strength 1670MPa 1670MPa 1670MPa 1670MPa

Breaking load 4,951kN 6,919kN 7,312kN 12,034kN

Elastic modulus 2.0E5MPa 2.0E5MPa 2.0E5MPa 2.0E5MPa

� Strength verification

As described in B3.5.3.1, the hanger has been checked for both ULS and SLS.

Limit state Hanger No.1

side span

Hanger No.24

at tower

Hanger No.56

main span

ULS

ULS 4.04 6.92 2.63

FRD_ULS 4.88 8.02 3.30

Utilization ratio 0.83 0.86 0.80

Check O.K O.K O.K

SLS

SLS 2.98 5.12 1.94

FRD_SLS 3.29 5.42 2.23

Utilization ratio 0.91 0.94 0.87

Check O.K O.K O.K

- 166 -

(2) ULS design

(3) SLS design

FRD = 0.45 Fuk

B.3.5.3.3 Other cable structures

(1) Cable bands

Function of a cable band is to hold the hanger and connect it to the main cable without significant

decrease in the main cable strength. Hence the band will not be compressed more than moderate level.

The compressive force may cause adverse lateral pressures to cable wires and an increase in friction

between individual wires. In such a case, the main cable tends to behave more rigidly (beam action)

which may cause an unfavorable effect.

However, the banding effect by tensioning of the tie rods will assure that the band does not slip on the

main cable, when the band is loaded by increased hanger force from traffic.

Cable bands have been designed in accordance with the Eurocode. The friction between the zinc-

coated wires and the saddle trough is assumed to be µ= 0.20.

=R

k

R

ukRD

FFF

γγ,

5.1min1≤

RD

ED

F

F

1≤RD

ED

F

F

- 167 -

� Material

The cast steel has the following characteristics (SCW550 grade or equivalent):

fa = 209MPa fy = 355MPa fu = 550MPa

The band bolts are (SCM440 grade or equivalent):

fa = 491MPa fy = 834MPa fu = 981MPa

� Design of cable bands

Items TYPE-1 TYPE-2 TYPE-3 TYPE-4 TYPE-5

Material Band SCW550 SCW550 SCW550 SCW550 SCW550

Bolt SCM440 SCM440 SCM440 SCM440 SCM440

Band length 2000mm 1200mm 1400mm 1600mm 3000mm

Num. of bolts 20 EA 12 EA 14 EA 16 EA 30 EA

Thickness 38mm 38mm 38mm 38mm 38mm

Sliding check 8.92 > 1.65 4.26 > 1.65 4.20 > 1.65 3.64 > 1.65 2.89 > 1.65

Separate check 2.08 > 1.65 1.96 > 1.65 2.31 > 1.65 2.37 > 1.65 1.98 > 1.65

Hoop stress 137MPa 137MPa 137MPa 137MPa 137MPa

Contact pressure 11.6MPa 11.6MPa 11.6MPa 11.6MPa 11.6MPa

(2) Tower saddles

The tower saddles, installed on the bent in order to make the main cable pass through the top of the

tower, act as a structure transmitting reaction force of main cable to the tower. The trough of the

saddle is made of cast steel, whereas its body structures are made of structural steel plates.

� Design of Tower Saddle

Classification Values Remarks

Trough Material SCW550 fa= 209MPa / fy=355MPa / fu=550MPa

Curvature R1=7250mm / R2=6250mm

Web

Material HSB500 fa= 220MPa / fy=380MPa / fu=500MPa

Number Main 2NOS

Rib 16NOS

Base Material HSB500 fa= 220MPa / fy=380MPa / fu=500MPa

- 168 -

� Stress Check

Classification Stress check Remarks

Trough

Deck plate f = 78MPa < fa=209MPa O.K

Side wall f = 77MPa < fa=209MPa O.K

Web f = 125MPa < fa=220MPa O.K

Base f = 122MPa < fa=220MPa O.K

(3) Splay Saddles

Splay saddles fix main cables to the anchorage and ensure that the main cables are spread out with a

strand as a unit.

The splay saddles are composite structures that transmit load directly. The trough of the saddle is

made of cast steel, whereas other members are made of steel plate.

� Design of Splay Saddles

Classification Values Remarks

Trough

Material SCW550 fa= 209MPa / fy=355MPa / fu=550MPa

Curvature

RV R1=7,500mm / R2=5,500mm

RH RH = 21,752mm

Web

Material HSB500 fa= 220MPa / fy=380MPa / fu=500MPa

Number of web 2NOS

Base Material HSB500 fa= 220MPa / fy=380MPa / fu=500MPa

� Stress Check

Classification Stress check Remarks

Trough

Deck plate f = 112MPa < fa=209MPa O.K

Side wall f = 152MPa < fa=209MPa O.K

Web f = 174MPa < fa=220MPa O.K

Base f = 112MPa < fa=220MPa O.K

- 169 -

B.3.5.4 Towers

The main towers are portal shaped frame structures consist of two slightly inclined legs

interconnected by 4 cross beams at the top and at intermediate levels between the foundation and the

tower top. The tower legs are supported on two separate circular jacket type foundations.

B.3.5.4.1 Cross Section

The towers, slightly tapered from 6.5m × 10m at the bottom to 6.5m × 6.5m at the top, have

rectangular cross section with square corner cuts. The general elevation and cross sections of the

tower legs are as shown below.

Cross Sections

Classifications Units Values Symbols

Steel grade - HSB 600

Yield strength N/mm2 450 fy

Ultimate tensile strength N/mm2 600 fu

Modulus of elasticity N/mm2 210,000 E

Shear modulus N/mm2 81,000 G

- 170 -

Partial Safety Factors

The partial factors applied to the characteristic values of resistance are tabulated as follows.

Resistance values Partial factors Value Remark

Cross sections γM0 1.0

Members γM1 1.1

B.3.5.4.2 Linear Buckling Analysis

To estimate the effective buckling length of the tower leg, elastic buckling analysis is carried out for

the completed bridge using RM2006. The effective buckling length of each element is derived from

the critical buckling forces for Euler column. Buckling safety factors for three buckling modes are

shown below.

Mode No. Buckling factor Description

1 4.608 tower's 1st mode in longitudinal direction

3 12.087 tower's 1st mode in transverse direction

4 11.921 tower's 2nd mode in longitudinal direction

1st mode : longitudinal direction

3rd mode : transverse direction

- 171 -

B.3.5.4.3 Design force for ULS combination

Axial force Nx (kN) Bending moment Mz (kN∙m) Bending moment My (kN∙m)

Shear force Qz (kN) Shear force Qy (kN)

- 172 -

B.3.5.4.4 Verifications

Cross section properties

It is assumed that all cross sections are classified to Class 4 in which local buckling will occur prior to

the attainment of yield stress. The effects of local buckling and shear lag are considered by effective

width method which reduces resistance instead of the yield strength.

Check buckling effects of plate

The resistance of plated members is determined using the effective areas of plate elements in

compression for Class 4 sections using cross sectional properties (Aeff, Ieff, Weff) for cross sectional

verifications and member verifications for column buckling and lateral buckling according to EN

1993-1-1. Effective areas are determined on the basis of the linear strain distribution with the

attainment of yield strain in the mid plane of the compression plate.

Fiber stress points

Check resistance of cross section

The design value of a loading effect in each cross section does not exceed the corresponding design

resistance and if several loading effects act simultaneously the combined effect does not exceed the

resistance for that combination.

Members which are subjected to combined bending and axial force satisfy:

1/// 0min..

.

0min..

.

0

≤+

++

+⋅ Myzeff

NzEdEdz

Myyeff

NyEdEdy

Myeff

ED

fW

eNM

fW

eNM

fA

N

γγγ

where, Aeff is the effective area of the cross section when subjected to uniform compression

Weff.min is the effective section modulus (corresponding to the fibre with the maximum

elastic stress) of the cross section when subjected only to moment about the relevant axis

eN is the shift of the relevant centroidal axis when the cross section is subjected to

compression only

For all elements, the capacity of cross sections along the height of the main towers has been verified

to be satisfactory. The verification and limit criteria are plotted along the height of the tower as shown

below.

- 173 -

Cross section check in bending and axial force – ULS load combinations

Cross section check in bending and axial force – Accidental load combinations

Check buckling resistance of members

(1) Uniform members in compression

A compression member is verified against buckling as follows:

0.1.

≤Rdb

Ed

N

N

where, NEd is the design value of the compression force

Nb.Rd is the design buckling resistance of the compression member

- 174 -

For axial compression in members the value of χ for the appropriate non-dimensional slenderness λ is

determined from the relevant buckling curve according to :

0.11

22≤

−Φ+Φ= χ

λχ but

where, [ ]2)2.0(15.0 λλα +−+=Φ

(2) Uniform members in bending

A laterally unrestrained member subjected to major axis bending is verified against lateral torsional

buckling as follows:

0.1.

≤Rdb

Ed

M

M

where MEd is the design value of the moment

Mb.Rd is the design buckling resistance moment

Beams with sufficient restraint to the compression flange are not susceptible to lateral-torsional

buckling. In addition, beams with certain types of cross sections, such as square or circular hollow

sections, fabricated circular tubes or square box sections are not susceptible to lateral-torsional

buckling. Therefore, the reduction factor for lateral-torsional buckling is χLT = 1.0 .

(3) Uniform members in bending and axial compression

Members which are subjected to combined bending and axial compression satisfy:

1.

..

.

.. ≤∆+

+∆+

+

Ml

Rkz

EdzEdzyz

Ml

Rky

LT

EdyEdy

yy

Ml

Rky

Ed

M

MMk

M

MMk

N

N

γγχ

γχ

1.

..

.

.. ≤∆+

+∆+

+

Ml

Rkz

EdzEdzzz

Ml

Rky

LT

EdyEdy

zy

Ml

Rkz

Ed

M

MMk

M

MMk

N

N

γγχ

γχ

where, NEd, My.Ed and Mz.Ed are the design values of the compression force and the maximum

moments about the y-y and axis along the member, respectively

∆My.Ed, ∆Mz.Ed are the moments due to the shift of the centroidal axis

Χy and Χz are the reduction factors due to flexural buckling

ΧLT is the reduction factor due to lateral torsional buckling

kyy, kzz,kzy,kzz are the interaction factors

- 175 -

(4) Interaction factor

The interaction factors according to EN 1993-1-1 : Annex B are not applied for member check

because a large displacement analysis including second order effect (P-δ effects) is carried out in global structural analysis.

Therefore, the value of 1.0 is applied for all elements as the interaction factor in the resistance check.

(5) Summary for all elements

Uniform members in bending and axial compression (major axis) – ULS load combinations

Uniform members in bending and axial compression (major axis) – Accidential load combinations

- 176 -

Check shear resistance of members

(1) Check the resistance for shear

For unstiffened or stiffened webs the design resistance for shear are taken as :

Ml

hfVVV

wtyw

RdbfRdbwRDb⋅

⋅⋅≤+=

γ

η

3...

in which the contribution from the web is given by :

Ml

wyww

Rdbw

thfV

γ

χ

3.

⋅⋅⋅=

and the contribution from the flanges Vbf, Rd is not considered in this calculation.

The resistance for shear satisfies the following criteria.

0.1.

3 ≤=Rdb

Ed

V

Vη

(2) Interaction among shear force, bending moment and axial force

Provided that η3 does not exceed 0.5, the design resistance to bending moment and axial force need

not to be reduced to allow for the shear force. If η3 is more than 0.5, the combined effects of bending

and shear in the web of an I or box girder satisfy:

( )Rdpl

Rdf

Rdpl

Rdf

M

Mfor

M

M

.

.

1

2

3

.

.

1 0.1121 ≥≤−

−+ ηηη

Therefore, there is no need to consider the interaction effect.

(3) Summary of shear check

- 177 -

B.3.5.4.5 Tower foundation

Structural description

The steel foundation consists of top and bottom yoke plates

connected by vertical shear plates and pile sleeves. The

shear plates radiate from the tubular Ø12000 mm leg

towards the pile sleeves. The space between the inside of

the pile sleeves and the outer skin of the pile will be

grouted once the piles are installed, giving a rigid

connection between foundation and piles.

Jacket Foundation

Material properties Unit Tubular leg Steel plate Stiffener Steel pile

Steel grade - HSB 600 HSB 600 HSB 600 SM520

Yield strength(fy) MPa 450 450 450 360

Ultimate tensile strength(fu) MPa 600 600 600 520

Modulus of elasticity(E) MPa 210,000 210,000 210,000 210,000

Element models and analysis

(1) Finite element model

The tower foundation is modeled as a finite element structure using STAAD-Pro. The model is

limited to one foundation leg and to parts situated from 15m below the water line. The foundation

structure is modeled using plate elements, whereas piles and the jacket leg using beam elements.

Plan of yoke plate (Section A)

- 178 -

(2) Beam model

STAAD-Pro is used for creating a beam grid model. The foundation structure is represented by I-

profiles between the tubular jacket leg and the piles. Each shear plate is given a flange based on

effective width of the top and bottom yoke plates.

Finite element model - STAAD Beam model

Results

(1) Shear plates

Earthquake and vessel collision loads give the largest stresses in the shear plates.

The table below summarizes the design stresses for the relevant load cases for the given shear plate

with thickness of 45 mm:

Load case Shear plate connected to

pile no

Max Von Mises stress

fy=450MPa

Max shear stress

τy=260MPa

Vessel collision 1 9 420~450MPa 210~240MPa

Vessel collision 2 10 390~420MPa 180~210MPa

Earthquake 1 7 390MPa 210MPa

Earthquake 2 10 420~450MPa 250MPa

The Von Mises stress levels in the shear plates are very close to the yield strength. Shear stress gives

the largest contribution to the Von Mises stress for all load combinations. Therefore increased plate

thickness is the best approach for reducing plate stress. An increase of thickness from 45mm to 50

mm gives 11% extra capacity or stress reduction, i.e. Von Mises stress of 450MPa in a 45mm plate is

reduced to 405MPa.

- 179 -

Vessel collision – Von Mises stresses Earthquake – Von Mises stresses

(2) Yoke Plates

The yoke plates are subject to lower stresses than the shear plates. The Von Mises stresses are below

390MPa (except for some hot spots due to the FE method). Vessel collision forces give higher stresses

than earthquake loads.

Vessel collision – Von Mises stresses Earthquake – Von Mises stresses

f=330MPa < fy=450MPa O.K f=240~270MPa < fy=450MPa O.K

(3) Tubular leg

① Stiffeners

The chosen ring stiffeners prevent local shell buckling from developing at stress levels below the

yield strength (cross section class ≤3).

The actual leg thickness is 60mm and longitudinal flat bar stiffeners 430×50mm with 650mm

spacing on the inside of the tube give an equivalent (smeared) thickness of 93mm (for the calculation

of longitudinal membrane stresses).

The longitudinal stiffeners give the tube a characteristic buckling stress equal to 434MPa, i.e.

reducing the design stress resistance by 3.6% compared to yield stress limit.

The necessary ring stiffener cross section, given 5m spacing between stiffeners, is shown below.

- 180 -

Cross section of one ring stiffener including effective flange area

② Cross section capacity

The Von Mises utilisation ratios for the tubular leg cross section, given equivalent thickness 93mm

and reduced stress resistance (fy=434MPa), are shown in the table below. Maximum utilisation ratio is

0.83, due to vessel collision in the main direction

CASE COMB

Axial

(kN)

Shear

(kN)

Bending

(kN·m)

Tors.

(kN·m) Stress

utilization M-dir L-dir N-dir Abt.L Abt.N Abt.M

S1 EQ Max MN -291,678 63,766 8,569 323,036 2,683,289 90,114 0.80

S2 AC SHIP1 maxF -468,243 96,931 13 -437 2,004,046 -109 0.76

S3 AC SHIP2 maxN -400,006 -6,394 -86,249 2,525,767 -239,375 -136,528 0.83

S4 EQ Min PM -500,782 -23,870 -28,133 -834,105 -778,017 -56,174 0.59

(4) Pile sleeve grout connection

This is a traditional offshore jacket pile connection extensively used worldwide. The grout annulus is

about 9m long and the annulus thickness measures 71mm. Both pile and sleeve have 14mm high weld

beads with a spacing of 350mm which serve as shear keys. There are spacer plates inside the sleeve to

ensure concentric location of pile relative to sleeve.

- 181 -

① Grout properties

The grout consists of standard Portland

cement mixed with water. The critical

parameter is the mixing, i.e. to obtain correct

water/cement ratio. In this manner, cube

strength of 60MPa is readily achieved.

Standard grout will not expand, but may

shrink. However, this has no negative effects

in small annuli (typical thickness <100 mm).

The durability of the grout is comparable with

concrete, which has shown to be excellent for

high density/strength applications. In addition

since the grout is protected/contained by pile

and sleeve, there are few environmental

impacts.

Special grout is sometimes used, particularly if extra high strength is required (typically 80-120MPa)

and/or special qualities are required such as fast setting, non-shrinkage, expanding qualities.

② Design check of grout connection

� Design rules

The grouted connection between pile sleeve and pile head is calculated using NORSOK standard N-

004 Design of steel structures, rev 2, October 2004. The NORSOK standards are developed and

owned by the Norwegian petroleum industry and used for the design of Norwegian offshore structures.

� Calculations

Chapter K.5.3 in N-004 gives the strength of a grouted connection.

The following input values are assumed:

- Characteristic cube strength of grout, fck 60Mpa

- Effective grouted connection length, Le 7.5m

- Steel-grout elastic modular ratio, m 18

- Design axial force, NSd 60MN

- Material factor for interface transfer strength, γM 2.0

- Characteristic interface transfer strength, fbk 2.455MPa

- Design interface transfer stress, τbSd 1.04MPa

- Utilization ratio, τbSd / ( fbk/ γM) 0.85

Pile sleeve with grout-filled void

- 182 -

③ Results and conclusion

The connection capacity is larger than the design force. The utilisation ratio for the connection is 85%.

The grout is sensitive to relative pile to sleeve movement during the first 24h after grouting, reducing

the grout strength if movements are too large. Given the rather calm waters of Izmit Bay, full grout

capacity is not difficult to achieve.

B.3.5.5 Anchorages

B.3.5.5.1 General

The site conditions of the anchorages are quite different at the North and South sides. The foundation

of the north anchorage is designed as gravity type while the south is designed as piled foundation. For

the north anchorage, a massive concrete footing with a stepped bottom face is designed. In this way

the resistance to sliding force acting in the direction of the inclined bottom surface is much bigger

than the resistance to the sliding force for a block with horizontal bottom face. This can significantly

reduce the weight of the anchorage.

The geometry of anchorages is identical with two inclined frame structures comprising the splay

chambers and the supporting columns for the splay saddles referred as saddle leg. A cross beam is

provided at the top between the two inclined frames to improve the lateral resistance of the structures.

The incident angle of the main cable at splay saddle is 8.225˚ and the refraction angle of 40˚ is set to

control deviation angles of the main cable at the saddle.

The north anchorage The south anchorage

Concrete type fctm

(MPa) fctk,0.05 (MPa)

Ecm

(MPa) Ecd =Ecm/γcE

(MPa) Applications

C35 3.2 2.2 28,900 25,700 Anchorage

C40 3.5 2.5 29,750 24,800 Bored pile

- 183 -

B.3.5.5.2 North anchorage

Cable forces

The main cable forces from global analysis and the resultant supporting reaction at splay saddle acting

on the inclined supporting block are shown in the following table for one side of main cables only.

Forces per cable G

(Permanent)

Q (Variable) A(Accidental)

Traffic Wind Temp. EQ

Cable force (kN) 253,230.0 94,916.0 21,471.0 3,472.0 40,787.0

Reaction at saddle (kN) 138,643.1 51,996.4 11,755.3 1,900.9 22,330.8

Foundation A - saddle leg footing

(1) Loads

Classification V (MN) H (MN) x (m) y (m) V · x H · y V·x + H·y

G

Self weight. 398.9 0.196 78.4 0.0 78.4

Buoyancy 0.0

Cable force(SW) 253.092 113.280 0.000 8.000 0.0 906.2 906.2

Q

Cable force (L) 94.864 42.460 0.000 8.000 0.0 339.7 339.7

Cable force (W) 21.459 9.605 0.000 8.000 0.0 76.8 76.8

Cable force (T) 3.470 1.553 0.000 8.000 0.0 12.4 12.4

A Earthquake 112.010 8.415 0.0 942.6 942.6

Cable force (EQ) 40.765 18.246 0.000 8.000 0.0 146.0 146.0

(2) Stability analysis

ULS (EQU) combination action is applied to resistance to overturning. ULS (EQU) and ULS

(Seismic) combination action is applied to resistance to sliding. V and H of component cable force,

obtained from the load combination feasibility study, are multiplied by partial safety factor.

① Stability checks

Classification

Overturning (MN·m) Sliding (MN)

Overturning

force

Stabilizing

force

Utilization

ratio

Sliding

force

Resistance

force

Utilization

ratio

ULS (EQU) 1,454 11,404 0.13 181.7 482.9 0.38

ULS

(Seismic) - - - 251.6 341.2 0.74

- 184 -

(3) Bearing pressure analysis

ULS (EQU) and ULS (STR/GEO) are applied to bearing pressure analysis.

① Load combination 1 – ULS (EQU)

Classification

Σ V Σ M e Bearing pressure Utilization

ratio (MN/m) (MN·m/m) (m) Max

(kPa)

Min

(kPa)

Resistance

(kPa)

GK Anchorage-SW 8.4 1.6 0.2 178.8 170.2

QK Cable Force 8.1 29.1 3.6 244.9 93.4

SUM 15.1 27.1 1.8 385.1 244.1 1466.0 0.26

② Load combination 2 – ULS (STR/GEO)

Classification

Σ V Σ M e Bearing pressure Utilization

ratio (MN/m) (MN-m/m) (m) Max

(kPa)

Min

(kPa)

Resistance

(kPa)

GK Anchorage-SW 10.8 2.1 0.2 229.9 218.9

QK Cable force 9.6 34.5 3.6 290.7 110.9

SUM 20.4 36.6 1.8 520.6 329.8 2052.0 0.25

For all load combinations, it has been verified that the bearing capacity of foundation is satisfactory.

Foundation B – anchor block footing

(1) Loads

Classification V (MN) H (MN) x (m) y (m) V · x H · y V·x + H·y

G

Self weight 1,568.6 -3.109 -4,877.1 0.0 -4,877.1

Buoyancy 0.0

Cable force(SW) -325.5 388.0 7.046 24.718 -2,293.8 9,589.9 7,296.1

Q

Cable force (L) -122.0 145.4 7.046 24.718 -859.8 3,594.5 2,734.7

Cable force (W) -27.6 32.9 7.046 24.718 -194.5 813.1 618.6

Cable force (T) -4.5 5.3 7.046 24.718 -31.4 131.5 100.0

A EQ 440.5 8.415 0.0 3,706.6 3,706.6

Cable force (EQ) -52.4 62.5 7.046 24.718 -369.5 1,544.6 1,175.2

- 185 -

(2) Stability analysis

ULS (EQU) of combination action is applied to resistance to overturning. ULS (EQU) and ULS

(Seismic) of combination action are applied to resistance to sliding. V and H of component cable

force, obtained from the load combination feasibility study, are multiplied by partial safety factor.

① Resultant summary

Classification

Overturning (MN·m) Sliding (MN)

Overturning

force

Stabilizing

force

Utilization

ratio Sliding force

Resistance

force

Utilization

ratio

ULS (EQU) 21,125 38,272 0.55 350.7 699.5 0.50

ULS (Seismic) - - - 609.0 650.4 0.94

(3) Bearing pressure analysis

ULS (EQU) and ULS (STR/GEO) are applied to bearing pressure analysis.

① Load combination 1 – ULS (EQU)

Classification

Σ V Σ M e Bearing pressure Utilization

ratio (MN/m) (MN-m/m) (m) Max

(kPa)

Min

(kPa)

Resistance

(kPa)

GK Anchorage-SW 27.5 -85.3 -3.1 349.6 794.2

QK Cable force -8.7 195.1 -22.4 326.6 -689.3

SUM 18.5 109.7 5.9 676.3 104.9 1466.0 0.46

② Load combination 2 – ULS (STR/GEO)

Classification

Σ V Σ M e Bearing pressure Utilization

ratio (MN/m) (MN-m/m) (m) Max

(kPa)

Min

(kPa)

Resistance

(kPa)

GK Anchorage-SW 35.3 -109.7 -3.1 449.5 1021.1

QK Cable force -10.3 231.5 -22.4 387.7 -818.2

SUM 25.0 121.8 4.9 837.3 202.9 2052.0 0.41

For all load combinations, it has been verified that the bearing capacity of foundation is satisfactory.

- 186 -

Check the cross section

(1) Saddle Leg

① Design member force

Classification Axial (kN) Shear (kN) Moment (kN·m)

Longitudinal Transverse Longitudinal Transverse

ULS (STR/GEO) -334,851 12,110 -1,226 -112,159 16,852

ULS-seismic X -255,042 553 -11,927 -196,352 306,121

ULS-seismic Y -245,390 8,923 -36,004 -105,139 965,503

② P-M interaction check

fck=35Mpa, fyk=400Mpa

fcd=

fck

=

35

= 23.3 Mpa

fyd=

fyk

=

400

= 348 Mpa

γm 1.5

γm 1.15

Longitudinal direction Transverse direction

The longitudinal reinforcement ratio for the saddle leg is approximately 1.4%, which is determined to

satisfy the minimum ratio criteria of longitudinal reinforcement for compression components

specified.

(2) Splay chamber

① Design member force

Classification Axial (kN) Shear (kN) Moment (kN-m)

Longitudinal Transverse Longitudinal Transverse

ULS (STR/GEO) -46,892 27,797 885 -531,201 -12,439

ULS-seismic X 40,421 30,419 15,494 -600,136 -525,091

ULS-seismic Y -74,489 22,310 52,911 -427,561 -1,670,359

- 187 -

② P-M interaction check

fck=35Mpa, fyk=400Mpa

fcd= fck

= 35

= 23.3 Mpa

fyd= fyk

= 400

= 348 Mpa γm 1.5

γm 1.15

Longitudinal direction Transverse direction

The longitudinal reinforcement ratio for the splay chamber is approximately 1.8%, which is

determined by the minimum ratio criteria of longitudinal reinforcement for compression components

specified in EC2.

B.3.5.5.3 South anchorage

Cable forces

The main cable force from global analysis and the resultant supporting reaction at splay saddle acting

on the inclined supporting block are shown in the following table for one side of main cables only.

Forces per cable G

(Permanent)

Q (Variable) A (Accidental)

Traffic Wind Temp. EQ

Cable force (kN) 253,230.0 94,916.0 21,471.0 3,472.0 40,787.0

Reaction at saddle

(kN) 138,643.1 51,966.4 11,755.3 1,900.9 22,330.8

- 188 -

Check foundation

(1) Applied load summary

Classification V (MN) H (MN) x (m) y (m) V · x H · y V·x + H·y

G

Self weight 2,034.2 -11.456 -23,302.7 0.0 -23,302.7

Buoyancy 0.0

Cable force(SW) -72.5 501.3 14.000 51.050 -1,014.4 25,588.8 24,574.5

Q

Cable force (L) -27.2 187.9 14.000 51.050 -380.2 9,591.2 9,211.0

Cable force (W) -6.1 42.5 14.000 51.050 -86.0 2,169.6 2,083.6

Cable force (T) -1.0 6.9 14.000 51.050 -13.9 350.8 336.9

A EQ 571.2 7.326 0.0 4,184.5 4,184.5

Cable force (EQ) -11.7 80.7 14.000 51.050 -163.4 4,121.5 3,958.1

(2) Cable force by combination of actions

Classification Cable force (MN) V (MN) H (MN) Remarks

ULS (STR/GEO) 964.340 -137.959 954.421 Member design,

Bearing pressure

ULS (EQU) 812.402 -116.223 804.046 Stability, Bearing pressure

ULS (Seismic) 624.270 -89.309 617.849 Seismic

SLS 712.522 -101.934 705.193 -

(3) Stability analysis

① Resultant load at the center of footing

Classification N (MN) H (MN) M (MN·m) Remarks

SLS 1,927.0 736.4 12,791.8

ULS (EQU) 1,910.7 848.5 18284.3 Pile design

ULS (STR/GEO) 2,000.0 1,000.5 17,578.4 Pile design

/ Member design

ULS (Seismic) 1,939.6 1,221.0 12,729.5 Pile design

② Verification of stabilities

See chapter B.3.6.2

- 189 -

Check the cross section

(1) Saddle leg and splay chamber

The cross sections of the saddle leg and splay chamber are the same as those of the north anchorage

and the section check is not required.

(2) Piles

Pile head forces and moments for a row of 11 piles for ULS (STR/GEO) and ULS (Seismic) are

tabulated as below.

① Load case ULS (STR/GEO)

Pile

Local pile head forces and moments

Axial force

(kN)

Lateral force

(kN)

Moment

(kN·m) Remark

No. 1 40,400 13,000 111,000 -

No. 11 2,030 13,000 111,000 -

② Load case ULS (Seismic)

Pile

Local pile head forces and moments

Axial force

(kN)

Lateral force

(kN)

Moment

(kN·m) Remark

No. 1 38,500 15,900 142,000 -

No. 11 3,730 15,900 142,000 -

The large moments are clamping moments at pile top (towards cable anchorage) which diminish

quickly in the first 10m layer of soil.

The following figures show the moments along the depth of No. 1 pile for ULS (Seismic).

- 190 -

ULS (Seismic)

③ Chosen cross sections

The most obvious feature about the anchor is the high level for shear forces. This generates peak local

moments in the upper part of the piles. The chosen arrangement is to use diameter 3.8m in the top 8m

of pile and 2.5m thereafter. This solution leads to a reasonable reinforcement arrangement with a

maximum of 2 layers of 2 off bundled 32mm reinforcement bars.

Distance from

foundation

Cross section

name

Pile

diameter Reinforcement bars

Reinforcement

amounts

Concrete

amounts

0 – 8m Type 1 3.8m

2Φ32mm centre distance

200mm. Inner and outer layer.

As = 0.18㎡ Ac = 11.2㎡

8 – 21m Type 2a 2.5m 2Φ32mm centre distance 200mm.

Inner and outer layer. As = 0.11㎡ Ac = 4.8㎡

21 –58.5m Type 2b 2.5m 2Φ32mm centre distance 200mm.

As = 0.06㎡ Ac = 4.9㎡