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university of communication and transport

Assess steel cable stayed bridges in

viet namProf.Dr. Nguyen Viet Trung

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General assessment of steel cable stayed bridge

The assessment of cable stayed bridges are carried out by load testing and reality activities.

And specially bridge monitoring system are installed to assess that activities bridge.


Contract dated 30th March 2005 on Loading test for Haiphong Binhbridge between CHODAI Co.,LTD and Center of Civil consulting, Research and Experiment – University of Transport and Communications.

-Based on load testing result at site of Binh bridge by Center of Civil consulting, Research and Experiment – University of Transport and Communications and Haiphong bridges Project manegement unit carried out on 15th, 16th August 2005.

-Documents of Binh bridge project.

- Specification for load testing of bridge on highway 22 TCN 243-98

Binh bridge on load testing


Main bridge (cable stayed bridge)

Measure stress of girder in longitudinal direction under the affect of standing still moving load on bridge

At mid-span sections of main spanAt mid-span sections of Haiphong side span

Measure deflection in vertical direction under the affect of standing still moving load on bridge

At mid-span sections of main spanAt mid-span sections of Haiphong side span

Measure vibration of main griders at middle spansWithout truckWith truck of 40km/h speechWith truck of 60km/h speech

contents of loading test Binh BRIDGE


Measure stress of bridge desk in longitudinal direction under the affect of standing still moving load on bridge

At mid-span sections of main spanAt mid-span sections of side span

Measure stress in cables under the affect of standing still moving load on bridgeAnchor cable and next to anchor cable at Haiphong side spanMid-cable and next to mid-cable at Haiphong side main span

Measure stress and displacement of head of pylonsMeasure stress under the affect of standing still moving load at foot of pylon

area section (spaced 0.3m apart from pylon door)

Measure displacement of head of pylons:Static horizontal displacement at head of pylons in longitudinal direction under the

affect of standing still moving load on bridge.

Displacement and dynamic stress with load of 40km/h and 60km/h speech.



Testing loadTesting load are 24 HUYNDAI trucks (Korean) loading with sand or

bliding stone to ensure the weight of each truck is about 24.03 to 24.98tons (80% of designed load). Detail of real weight of trucks are noted at Appendix.

Sketch of HUYNDAI truck with spacing between axles as follow:

Each truck is located to put the behind axles about 6m away fromthe ahead axles of the following truck.

Loading train is put on spans in different loading sketches to reach adverse loading effects of each of measuring sections.



In each of loading sketch, loading lane arrangement as follow:a- At eccentric position at lower stream,b- At center line,c- At eccentric position at upper stream.

Requirement of testing loadAll testing load shall be weighed for load checking (include legal

certification and minutes of checking at site). Testing load shall be arranged in diferent loading cases appropriate

with effects to measure.



Result of Loading test Binh BRIDGE

Result of loading test of main bridge (stayed-cable bridge) under the affect of testing load

Result of stress measurement of main gridersMaximum stress at compress position (the upper edge of steel grider)a. Mid-span section of main span of main griders (stayed-cable bridge)

59,34%59,34%97,6297,6233

64,12%64,12%105,50105,5022

The upper The upper edge of edge of

steel steel gridergrider(point 2t6(point 2t6’’))

57,71%57,71%164.52164.5294.9594.9511Stress Stress kG/cmkG/cm22

Maximum stress Maximum stress by testing by testing

moving loadmoving load

TimeTime

NoteNoteStress scale Stress scale between between

measurememeasurement and nt and theorytheory

TheoreticTheoretical al

calculate calculate numeric numeric

value value

Measurement resultMeasurement resultQuantityQuantity




b. Cross section near mid-span position of Haiphong side span (≈0.3LB) of main grider (stayed-cable bridge)

61.03%61.03%164.58164.5833

56.03%56.03%151.28151.2822

The upper The upper edge of edge of

steel steel gridergrider(point 2t6(point 2t6’’))

64.08%64.08%269.99269.99173.02173.0211Stress Stress kG/cmkG/cm22



TimeTime

NoteNoteStress scale Stress scale between between

measurement measurement and theoryand theory

Theoretical Theoretical calculate calculate numeric numeric

value value

Measurement resultMeasurement resultQuantitQuantityy




Maximum stress at strain position (the lower edge of steel grider)a. Mid-span section of main span of main griders (stayed-cable bridge)

67.10%67.10%432.55432.5533

64.18%64.18%413.56413.5622

The lower The lower edge of steel edge of steel gridergrider (point (point

2d52d5’’))


Maximum Maximum stress by stress by

testing moving testing moving loadload

TimeTime

NoteNoteStress Stress scale scale

between between measuremmeasurem

ent and ent and theorytheory

TheoreticTheoretical al

calculate calculate numeric numeric

value value





Maximum stress at strain position (the lower edge of steel grider)b. Cross section near mid-span position of Haiphong side span (≈0.3LB) of

main grider (stayed-cable bridge)

58.99%58.99%405.12405.1233

55.62%55.62%381.91381.9122

The lower The lower edge of steel edge of steel gridergrider (point (point

1d11d1’’))




TimeTime

NoteNoteStress Stress scale scale

between between measuremmeasurem

ent and ent and theorytheory

TheoreticaTheoretical calculate l calculate numeric numeric

value value





Commentary on stress measurement result in main griders of stayed-cable bridge part:

Stress measurement results under the affect of moving load whichhave been comparative verifyed are all smaller than theoretical calculated numerical values from 3D structural model analysis by MIDAS-Civil software (55.67 to 68.77%). That shows the big safety reserve of loading capacity of main span superstructure.

The maximum stress value by moving load is 443.10kG/cm2, is about 11.36% of permited loading capacity of steel in grider fy = 3900kG/cm2.




. Deflection measurement result of main griders

1/90321/903222,87%22,87%47,0047,0010,7510,75Side spanSide span

1 / 11201 / 112092,06%92,06%252,00252,00232,00232,00Middle of main Middle of main spanspan

ffhh /L/LScale %Scale %Calculation value Calculation value MeasuremeMeasurement valuent value

Maximum deflection (mm)Maximum deflection (mm)Cross sectionCross section

Deflection measurement result is appropriated with theoretical analytic result and is smaller than the permitted deflection value of AASHTO which is L/800 = 0.325m.




Stress measurement result at foot of pylon (Haiphong side)The maximum stress at foot of pylon (Haiphong side):

85,7585,75%%

14,9514,9512.8212.8279,6079,60%%

14,9514,9511,9011,90Stress Stress kG/cmkG/cm22

Scale Scale %%

CalculatioCalculation valuen value

MeasuremeMeasurement valuent value

Scale Scale %%

CalculatioCalculation valuen value

MeasuremeMeasurement valuent value

Point Point

Foot of pylon at Foot of pylon at lowerstreamlowerstreamFoot of pylon at Foot of pylon at uppstreamuppstreamCross Cross sectionsection

Stress values which were measured at foot of pylon at compress position are smaller than correlative theoretical calculate numeric values and much smaller than compress intensity of pylon’s material.




Displacement measurement result of head of pylon (Haiphong side)

101,1101,190,0090,0091,0091,00

Scale %Scale %Calculation valueCalculation valueMeasurement valueMeasurement value

Displacement result of head of pylon (Haiphong side) (mm)Displacement result of head of pylon (Haiphong side) (mm)




Vibrate measurement result of pylon of main bridge

0.3020.302Period (sec)Period (sec)

3.3153.315Frequency (Hz)Frequency (Hz)

Door of S9 pylonDoor of S9 pylonPositionPosition

Vibrate measurement result of main griders of main bridge

0.2450.245Period (sec)Period (sec)

4.0824.082Frequency (Hz)Frequency (Hz)

Middle of main spanMiddle of main spanPositionPosition

Vibrate frequency is in normal limitation.




Stress measurement result in stayed-cable

1.131.13869.54869.54980.69980.690.0980.0985146.555146.550.980.984168.864168.860.880.88S20S20

1.471.47645.75645.75949.52949.520.0980.0985688.565688.561.121.124739.044739.041.031.03S19S19

1.161.16708.45708.45823.60823.600.0970.0974775.184775.181.071.073951.583951.580.980.98S2S2

1.281.28694.41694.41889.57889.570.0970.0975157.635157.631.071.074268.064268.060.980.98S1S1

StressStressKg/cmKg/cm22

FrequeFrequencyncy(Hz)(Hz)


FrequFrequencyency(Hz)(Hz)


FrequFrequencyency(Hz)(Hz)

%%CalculatiCalculation stresson stressKg/cmKg/cm22

DifferenceDifferenceWith moving With moving loadload

Without moving Without moving loadloadCablCabl

ee

Frequency and stress values in cables under the affect of testing moving load are not large.



General conclusion

The loading test work of Binh bridge was completed exactly according to the daft which had been come to an agreement between CHODAI CO.,LTD and Center of Civil consulting, Research and Experiment – University of transport and communication.

Preliminary result shows that technical standards such as load capacity, strain stiffness, settlement, pier displacement, head of pylon’s displacement, eigen vibration period are all appropriate with theoretical analysis result and in the permitted limit.

The loading test process did not show any unusal expression to load bearing systems of the bridge.The Binh bridge of Haiphong was contructed appropriate with the design. The testing result shows that the construction has got enough ability for exploitting with design load.



Some commantaries

After taking into exploit, it is expected to carry out the right monitoring, checking, maintenance work for the construction, especially for the main bridge which is the stayed-cable one, by the management agency. Perfect some structure details such as the drainage system, lock of the door of pylons appropriated with design.


Photos on during Loading test of Binh BRIDGE


Main bridge (cable stayed bridge)

Measure stress of main girder at 4 sections Section No1: L/4 of beside spanSection No2: L/2 of beside spanSection No3: L/4 of midle spanSection No4: L/2 of midle span

Measure stress of some section of pylonAt the top of pylon No1 (to To Hieu street)At the top of pylon No2 (to Chu Van Thinh street)

Measure stress of some stayed cables: 12 stayed cables with 24 point of measurement

Measure stress of slap beamMeasure stress of transerver

contents of loading test Son la BRIDGE


contents of loading test Son la BRIDGE

Measure displacement of main gider at 6 sectionsSection No1: L/4 of beside spanSection No2: L/2 of beside spanSection No3: L/4 of midle spanSection No4: L/2 of midle spanAt the top of pylon No1 (to To Hieu street)At the top of pylon No2 (to Chu Van Thinh street)

Measure Displacement and dynamic stress with load of 40km/h and 60km/h speech at Section No4: L/2 of midle span and Section No2:L/2 of beside span


contents of loading test son la BRIDGE

Measure settlement and Displacement horizontal of top 2 pylons with 3 pionts for each one.

Measure settlement and lifting power at abutment M2 (to Chu Van Thinhstreet with 2 points.

Measure strength of concrete slab, piers, abutments (without destroy)


Result of Loading test son la BRIDGEResult of loading test of main girder of bridge (stayed-cable bridge) under the affect of testing load

Measure Stress of main girder

210.00210.00--216.30216.301/2 1/2 midlemidle spanspan

136.50136.50--231.00231.001/4 1/4 midlemidle spanspan

182.00182.00--238.00238.001/2 1/2 beside beside

spanspan

126.00126.00--220.50220.501/4 beside span1/4 beside span

Strain fiber (kG/cmStrain fiber (kG/cm22))Compress fiber (kG/cmCompress fiber (kG/cm22))

Maximums stress valuesMaximums stress valuesSectionSection

Stress values which were measured rather smaller than calculation


Result of Loading test son la BRIDGE

Result of loading test of cable stayed (stayed-cable bridge) under the affect of testing load

Measure Stress of cable stayed

401.00401.0066

514.60514.6055

413.00413.004 4

576.10576.1033

221.00221.0022

471.50471.5011

Maximums stress valuesMaximums stress values(kG/cm(kG/cm22))

Cable stayedCable stayed

Stress values which were measured rather smaller than calculation


Result of Loading test son la BRIDGE

Result of loading test of pylon (stayed-cable bridge) under the affect of testing load

Measure Stress of pylon

63.0063.001515

--126.10126.101414

--128.10128.101313

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--31.5031.501515

10.5010.501414

65.1065.101313

KhiKhi tt¶¶ii ëë vÞvÞ trÝtrÝ nhÞpnhÞp bibiªªnn

Maximums stress values (kG/cmMaximums stress values (kG/cm22))NoNo


Result of Loading test son la BRIDGEResult of loading test of main bridge (stayed-cable bridge) under the affect of testing load

Measure vabration

2.502.501.2981.2984.3804.3803.7303.7305.4705.470Middle Middle

2.632.631.3711.3713.0133.0132.4302.4303.9023.902Beside Beside

Frequency f (Hz)Frequency f (Hz)1 + 1 + µµyytbtbyyminmin

(mm)(mm)yymaxmax

(mm)(mm)spanspan

Measure Displacement

5.475.47Middle Middle

3.9023.902Beside Beside

Maximum displacement (mm)Maximum displacement (mm)spanspan


Photos on during Loading test of son la BRIDGE




summary

1. The cost of material of Steel Cable stayed bridges in countryside in viet nam is cheap, but the cost of construction is expensive.

2. The assessment maintenance difficultly, required knowledge.

3. There are two type steel cable stayed bridges. The first is Dakrong bridge. This is manufactured by vietnam. The stayed cable is best for cable stayed bridges. The cost and engineering is sensible. The second is binhbridge. That is perfect but the cost is very high.

4. The monitoring system for cable stayed bridges in vietnam are developing with all devices for assessment bridges.


Prof.Dr. Nguyen Viet Trung

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