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System identification of Bogazici suspension bridge during hanger replacement
Available online at www.sciencedirect.com
ScienceDirect ScienceDirect Procedia Engineering 00 (2017) 000–000
Available online at www.sciencedirect.com
www.elsevier.com/locate/procedia
ScienceDirect
www.elsevier.com/locate/procedia
Procedia Engineering 00 (2017) 000–000
Procedia Engineering 199 (2017) 1026–1031
X International Conference on Structural Dynamics, EURODYN 2017 X International Conference on Structural Dynamics, EURODYN 2017
System identification of Bogazici suspension bridge during hanger System identification of Bogazici suspension bridge during hanger replacement replacement a, b c a a
Serdar Soyoz *, Umit Dikmen , Nurdan Apaydin , Korkut Kaynardag , Emre Aytulun , a a b a, b Catbasd, Hilmi Lus a Oguz Senkardasler , Necati , ErdalKaynardag Safakb, Mustafa Serdar Soyoz *, Umit Dikmen , Nurdan Apaydinc, Korkut , EmreErdik Aytuluna, a d a b Oguz Senkardasler Necati CatbasBogazici , Hilmi LusBebek, , Erdal Safak , Mustafa Erdikb Department, of Civil Engineering, University, Istanbul 34342, Turkey a
b
Department of Earthquake Engineering, Bogazici University, Cengelkoy, Istanbul 34684, Turkey a c Department of Civil Engineering, Bogazici University, Bebek, 06100, IstanbulTurkey 34342, Turkey General Directorate of Highways, Yucetepe, Ankara ab Earthquake Engineering, Bogazici University, Cengelkoy, Department of Civil Engineering, University of Central Florida, Orlando,Istanbul Florida 34684, 32816, Turkey c General Directorate of Highways, Yucetepe, Ankara 06100, Turkey a Department of Civil Engineering, University of Central Florida, Orlando, Florida 32816, Turkey
Abstract Abstract Bogazici suspension bridge is one of the long-span bridges crossing over the Bogazici strait. It was opened to traffic in 1973 and from that day on it has been one of the most important links in the traffic network of Istanbul. It has a main span of 1074m and Bogazici suspension bridge one of the long-span crossing theInBogazici strait. It was opened to traffic in 1973 the original configuration ofisthe suspension hangersbridges was inverted - Vover shape. 2015, the suspension cables were replaced and and the from that day has been of the to most important links in campaign, the traffic network Istanbul. It has a main span of and orientation of on theitcables wasone changed vertical. During this vibrationofmeasurements were recorded on1074m the tower, the configuration the suspension hangers was inverted -were V shape. 2015, the suspension were replaced and the deckoriginal and the suspension ofcables of the bridge. Measurements takenIn at different stages ofcables this campaign to have an orientation of the cables wasofchanged to vertical.on During this campaign, vibration measurements were recorded were on the tower, understanding of the effects cable replacement the overall dynamic behaviour. Additionally, measurements recorded deck suspension the to bridge. Measurements were taken stages of this campaignResults to have an for at and leastthe several days to cables several of weeks observe operational variations on at thedifferent modal frequencies of vibration. show understanding of cabledominant replacement ondecreased the overallbydynamic measurements that frequenciesofofthe theeffects deck motion modes 6 to 12%behaviour. and there Additionally, were almost no change in thewere towerrecorded motion for at leastmodal several days to several to observe dominant frequencies due to weeks replacement of theoperational hangers. variations on the modal frequencies of vibration. Results show that frequencies of the deck motion dominant modes decreased by 6 to 12% and there were almost no change in the tower motion dominant modal frequencies due to replacement of the hangers. © 2017 The Authors. Published by Elsevier Ltd. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility responsibility of of the the organizing organizing committee committee of of EURODYN EURODYN 2017. 2017. Peer-review © 2017 The under Authors. Published by Elsevier Ltd. Peer-review under Suspension responsibility of the organizing committee of EURODYN 2017. Keywords: Bogazici Bridge; System Identification; Suspension Cable Keywords: Bogazici Suspension Bridge; System Identification; Suspension Cable
* Corresponding author. Tel.: +90-212-3597788; fax: +90-212-287-2457. E-mail address: [email protected] * Corresponding author. Tel.: +90-212-3597788; fax: +90-212-287-2457. E-mail address: [email protected] 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of EURODYN 2017. 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of EURODYN 2017.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of EURODYN 2017. 10.1016/j.proeng.2017.09.275
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Serdar Soyoz et al. / Procedia Engineering 199 (2017) 1026–1031 S.Soyoz et al.// Procedia Engineering 00 (2017) 000–000
1027
1. Introduction Structural Health Monitoring (SHM) may be described as measuring the response, analyzing the collected data to identify the dynamic characteristics, and evaluating the current status of a structure. SHM has two main objectives: The first objective is to evaluate aluate the “health” of a structure after a major shock (such as an earthquake). The second objective is to estimate dynamic properties of structures using small amplitude “ambient” vibrations. Here the aim would to be use these properties to update representative numerical models of structures so as to improve the predictive capabilities of the models to accurately estimate structural response under strong inputs such as earthquakes. SHM efforts are especially important for critical structures such as as suspension bridges. These types type of bridges have no redundancy in the traffic network and their failure would be catastrophic. This is also the case for suspension bridges in Istanbul which link Europe to Asia. There are three suspension bridges over the Bosphorus; namely, Bogazici (Ataturk), Fatih Sultan Mehmet and Yavuz Sultan Selim Bridges. General Directorate of Highways (GDH)) operates a permanent SHM system on Bogazici Bridge which consists of different sensors such as acceleration sensors (to measure response of tower, deck and cables), strain gauges (for fatigue of the deck and cables), force transducers (to measure Force on cables), laser sensors (to measure relative displacement between tower and deck), GPS stations (to measure movement of tower), tiltmeters, thermo couples, weather stations. In addition to efforts by GDH there have been both analytical and experimental studies on the Bridge throughout years such as [1, 2, 3, 4, 5] In this paper, a recent study by the Departments of Civil and Earthquake Earthquake Engineering at Bogazici University was summarized. The main motivation of this study was to record and analyze vibration response to understand how dynamic characteristics of Bogazici Suspension Bridge change during its structural retrofitting (inclined (inclin hangers were changed to vertical ones). Identification of dynamic characteristics of the Bridge using vibration data collected within this project allowed us to conduct research which has not been carried out previously. 2. Bridge Definition Bogazici suspension ension bridge is the first suspension bridge in Istanbul connecting Europe and Asia. It was commissioned in 1973. It is a gravity anchored suspension bridge with a main span of 1074 m. The original configuration of the hangers was inclined and as discussed in this paper their configuration was recently ntly changed to vertical. Fig. 1 shows general view of the Bridge and elevation view of towers and section view of deck.
Fig. 1. General view of Bogazici Suspension Bridge
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Serdar Soyoz et al. / Procedia Engineering 199 (2017) 1026–1031 S. Soyoz et al./ Procedia Engineering 00 (2017) 000–000
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Fig. 2 shows the hanger replacement during which vertical hangers were placed to their positions and then tension force was transferred from inclined to vertical cables pair by pair.
Fig. 2. Change of hangers
3. Instrumentation and data analysis Main motivation of the study was to investigate the change in the dynamic characteristics of the Bridge during the replacement of hangers. As shown in Fig. 3 and 4, sensors were located on different locations of towers and deck. Synchronized data was gathered to obtain mode shapes of the Bridge. Vibration data was measured also from hangers to determine the force based on the identified frequencies. Vibration data was collected for the following periods: • April 2015 : Inclined Hangers
• July-August 2015 • May-June 2106
: Replacement Period : Vertical Hangers
Fig. 3. Sensor Layout
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Serdar Soyoz et al. / Procedia Engineering 199 (2017) 1026–1031 S.Soyoz et al.// Procedia Engineering 00 (2017) 000–000
1029
Fig. 4. Sensors and DAQ
Fig. 5 shows representative vibration data collected from tower top in transverse and longitudinal directions and from deck mid-span span in transverse and vertical directions. As can be seen from measurement amplitudes, main vibration of the Bridge is in vertical direction and this effect is also observed in the frequency domain results.
Fig. 5. Vibration data
Modal values such as frequencies and shapes were obtained using Frequency Domain Decomposition method. This output-only only method is powerful especially to identify close modes. In this method, square matrices whose indices are the cross power spectral density y of the data from different sensors are generated for each frequency output. The singular value decomposition of those matrices gives modal frequencies and shapes. Fig. 6 shows modal frequencies of tower and deck and Fig. 7 shows the corresponding mode shapes.
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Fig. 6. PSD of tower and deck
Fig. 7. Mode shapes
4. Variation of modal frequencies Vibration data collected before, during and after the structural retrofitting campaign was processed as discussed above. Fig. 8 shows how modal frequencies change during this period. Based on the values summarized in Table 1, modal frequencies of the bridges were decreased by as much as 12 % which may be expected due to changes in the configuration of hangers. It was also observed that tower frequency did not change during this period. All these findings will also be investigated through analytical models which will allow us to understand the reason why deck frequency changes due to hanger change.
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Serdar Soyoz et al. / Procedia Engineering 199 (2017) 1026–1031 S.Soyoz et al./ Procedia Engineering 00 (2017) 000–000
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Fig. 8. Deck modal frequency change Table 1. Change in Modal Frequencies Mode 1 (1st Lsym)
Before Retrofitting 0.074 Hz
During Retrofitting 0.076 Hz
After Retrofitting 0.081 Hz
2 (1st Vasym)
0.137 Hz
0.137 Hz
0.125 Hz
3 (1st Vsym)
0.159 Hz
0.154 Hz
0.149 Hz
4 (2nd Vsym)
0.217 Hz
0.215 Hz
0.201 Hz
5 (2nd Vasym)
0.276 Hz
0.262 Hz
0.243 Hz
5. Conclusion Vibration based monitoring of Bogazici Suspension Bridge during configuration change of hangers from inclined to vertical was carried out almost for one year. Results indicate that there is a clear decrease in the vertical modal frequencies of the deck. This and other findings need further analytical investigation using finite element model of the bridge. Experimental and analytical studies will eventually allow us to understand the dynamic behaviour of the Bridge in detail. Acknowledgements Authors from Departments of Civil and Earthquake Engineering of Bogazici University acknowledge the funding by Bogazici University BAP 10150 and Prof Catbas acknowledges the contribution of Tubitak 2221 project. We would also like to acknowledge the help of General Directorate of Highways staff at Bogazici Bridge References [1] S. Tezcan, M. Ipek, J. Petrovski, T. Paskalov, Forced Vibration Survey of Istanbul Bogazici Suspension Bridge, 5th European Conference on Earthquake Engineering, Istanbul, Turkey. (1975). [2] W. J.M.W. Brownjohn, A.A. Dumanoglu, R.T. Severn, A. Blakeborough, Ambient Vibration Survey of the Bosporus Suspension Bridge, Earthquake Engineering and Structural Dynamics, 18 (1989) 263-283. [3] G. M. Erdik, E. Uckan, Ambient Vibration Survey of the Bosporus Suspension Bridge, KOERI Report 89-5, Bogazici University, Istanbul, Turkey. (1989). [4] N.M. Apaydin, Earthquake Performance Assessment and Retrofit Investigations of Two Suspension Bridges in Istanbul, Soil Dynamics and Earthquake Engineering, 30 (2010) 702-710. [5] N.M. Apaydin, C. Zulfikar, E. Safak, Vibration Characteristics of Bogazici Suspension Bridge Using Structural Health Monitoring Data, 2nd Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures, Istanbul, Turkey. (2013).
ScienceDirect ScienceDirect Procedia Engineering 00 (2017) 000–000
Available online at www.sciencedirect.com
www.elsevier.com/locate/procedia
ScienceDirect
www.elsevier.com/locate/procedia
Procedia Engineering 00 (2017) 000–000
Procedia Engineering 199 (2017) 1026–1031
X International Conference on Structural Dynamics, EURODYN 2017 X International Conference on Structural Dynamics, EURODYN 2017
System identification of Bogazici suspension bridge during hanger System identification of Bogazici suspension bridge during hanger replacement replacement a, b c a a
Serdar Soyoz *, Umit Dikmen , Nurdan Apaydin , Korkut Kaynardag , Emre Aytulun , a a b a, b Catbasd, Hilmi Lus a Oguz Senkardasler , Necati , ErdalKaynardag Safakb, Mustafa Serdar Soyoz *, Umit Dikmen , Nurdan Apaydinc, Korkut , EmreErdik Aytuluna, a d a b Oguz Senkardasler Necati CatbasBogazici , Hilmi LusBebek, , Erdal Safak , Mustafa Erdikb Department, of Civil Engineering, University, Istanbul 34342, Turkey a
b
Department of Earthquake Engineering, Bogazici University, Cengelkoy, Istanbul 34684, Turkey a c Department of Civil Engineering, Bogazici University, Bebek, 06100, IstanbulTurkey 34342, Turkey General Directorate of Highways, Yucetepe, Ankara ab Earthquake Engineering, Bogazici University, Cengelkoy, Department of Civil Engineering, University of Central Florida, Orlando,Istanbul Florida 34684, 32816, Turkey c General Directorate of Highways, Yucetepe, Ankara 06100, Turkey a Department of Civil Engineering, University of Central Florida, Orlando, Florida 32816, Turkey
Abstract Abstract Bogazici suspension bridge is one of the long-span bridges crossing over the Bogazici strait. It was opened to traffic in 1973 and from that day on it has been one of the most important links in the traffic network of Istanbul. It has a main span of 1074m and Bogazici suspension bridge one of the long-span crossing theInBogazici strait. It was opened to traffic in 1973 the original configuration ofisthe suspension hangersbridges was inverted - Vover shape. 2015, the suspension cables were replaced and and the from that day has been of the to most important links in campaign, the traffic network Istanbul. It has a main span of and orientation of on theitcables wasone changed vertical. During this vibrationofmeasurements were recorded on1074m the tower, the configuration the suspension hangers was inverted -were V shape. 2015, the suspension were replaced and the deckoriginal and the suspension ofcables of the bridge. Measurements takenIn at different stages ofcables this campaign to have an orientation of the cables wasofchanged to vertical.on During this campaign, vibration measurements were recorded were on the tower, understanding of the effects cable replacement the overall dynamic behaviour. Additionally, measurements recorded deck suspension the to bridge. Measurements were taken stages of this campaignResults to have an for at and leastthe several days to cables several of weeks observe operational variations on at thedifferent modal frequencies of vibration. show understanding of cabledominant replacement ondecreased the overallbydynamic measurements that frequenciesofofthe theeffects deck motion modes 6 to 12%behaviour. and there Additionally, were almost no change in thewere towerrecorded motion for at leastmodal several days to several to observe dominant frequencies due to weeks replacement of theoperational hangers. variations on the modal frequencies of vibration. Results show that frequencies of the deck motion dominant modes decreased by 6 to 12% and there were almost no change in the tower motion dominant modal frequencies due to replacement of the hangers. © 2017 The Authors. Published by Elsevier Ltd. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility responsibility of of the the organizing organizing committee committee of of EURODYN EURODYN 2017. 2017. Peer-review © 2017 The under Authors. Published by Elsevier Ltd. Peer-review under Suspension responsibility of the organizing committee of EURODYN 2017. Keywords: Bogazici Bridge; System Identification; Suspension Cable Keywords: Bogazici Suspension Bridge; System Identification; Suspension Cable
* Corresponding author. Tel.: +90-212-3597788; fax: +90-212-287-2457. E-mail address: [email protected] * Corresponding author. Tel.: +90-212-3597788; fax: +90-212-287-2457. E-mail address: [email protected] 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of EURODYN 2017. 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of EURODYN 2017.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of EURODYN 2017. 10.1016/j.proeng.2017.09.275
2
Serdar Soyoz et al. / Procedia Engineering 199 (2017) 1026–1031 S.Soyoz et al.// Procedia Engineering 00 (2017) 000–000
1027
1. Introduction Structural Health Monitoring (SHM) may be described as measuring the response, analyzing the collected data to identify the dynamic characteristics, and evaluating the current status of a structure. SHM has two main objectives: The first objective is to evaluate aluate the “health” of a structure after a major shock (such as an earthquake). The second objective is to estimate dynamic properties of structures using small amplitude “ambient” vibrations. Here the aim would to be use these properties to update representative numerical models of structures so as to improve the predictive capabilities of the models to accurately estimate structural response under strong inputs such as earthquakes. SHM efforts are especially important for critical structures such as as suspension bridges. These types type of bridges have no redundancy in the traffic network and their failure would be catastrophic. This is also the case for suspension bridges in Istanbul which link Europe to Asia. There are three suspension bridges over the Bosphorus; namely, Bogazici (Ataturk), Fatih Sultan Mehmet and Yavuz Sultan Selim Bridges. General Directorate of Highways (GDH)) operates a permanent SHM system on Bogazici Bridge which consists of different sensors such as acceleration sensors (to measure response of tower, deck and cables), strain gauges (for fatigue of the deck and cables), force transducers (to measure Force on cables), laser sensors (to measure relative displacement between tower and deck), GPS stations (to measure movement of tower), tiltmeters, thermo couples, weather stations. In addition to efforts by GDH there have been both analytical and experimental studies on the Bridge throughout years such as [1, 2, 3, 4, 5] In this paper, a recent study by the Departments of Civil and Earthquake Earthquake Engineering at Bogazici University was summarized. The main motivation of this study was to record and analyze vibration response to understand how dynamic characteristics of Bogazici Suspension Bridge change during its structural retrofitting (inclined (inclin hangers were changed to vertical ones). Identification of dynamic characteristics of the Bridge using vibration data collected within this project allowed us to conduct research which has not been carried out previously. 2. Bridge Definition Bogazici suspension ension bridge is the first suspension bridge in Istanbul connecting Europe and Asia. It was commissioned in 1973. It is a gravity anchored suspension bridge with a main span of 1074 m. The original configuration of the hangers was inclined and as discussed in this paper their configuration was recently ntly changed to vertical. Fig. 1 shows general view of the Bridge and elevation view of towers and section view of deck.
Fig. 1. General view of Bogazici Suspension Bridge
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Serdar Soyoz et al. / Procedia Engineering 199 (2017) 1026–1031 S. Soyoz et al./ Procedia Engineering 00 (2017) 000–000
3
Fig. 2 shows the hanger replacement during which vertical hangers were placed to their positions and then tension force was transferred from inclined to vertical cables pair by pair.
Fig. 2. Change of hangers
3. Instrumentation and data analysis Main motivation of the study was to investigate the change in the dynamic characteristics of the Bridge during the replacement of hangers. As shown in Fig. 3 and 4, sensors were located on different locations of towers and deck. Synchronized data was gathered to obtain mode shapes of the Bridge. Vibration data was measured also from hangers to determine the force based on the identified frequencies. Vibration data was collected for the following periods: • April 2015 : Inclined Hangers
• July-August 2015 • May-June 2106
: Replacement Period : Vertical Hangers
Fig. 3. Sensor Layout
4
Serdar Soyoz et al. / Procedia Engineering 199 (2017) 1026–1031 S.Soyoz et al.// Procedia Engineering 00 (2017) 000–000
1029
Fig. 4. Sensors and DAQ
Fig. 5 shows representative vibration data collected from tower top in transverse and longitudinal directions and from deck mid-span span in transverse and vertical directions. As can be seen from measurement amplitudes, main vibration of the Bridge is in vertical direction and this effect is also observed in the frequency domain results.
Fig. 5. Vibration data
Modal values such as frequencies and shapes were obtained using Frequency Domain Decomposition method. This output-only only method is powerful especially to identify close modes. In this method, square matrices whose indices are the cross power spectral density y of the data from different sensors are generated for each frequency output. The singular value decomposition of those matrices gives modal frequencies and shapes. Fig. 6 shows modal frequencies of tower and deck and Fig. 7 shows the corresponding mode shapes.
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Fig. 6. PSD of tower and deck
Fig. 7. Mode shapes
4. Variation of modal frequencies Vibration data collected before, during and after the structural retrofitting campaign was processed as discussed above. Fig. 8 shows how modal frequencies change during this period. Based on the values summarized in Table 1, modal frequencies of the bridges were decreased by as much as 12 % which may be expected due to changes in the configuration of hangers. It was also observed that tower frequency did not change during this period. All these findings will also be investigated through analytical models which will allow us to understand the reason why deck frequency changes due to hanger change.
6
Serdar Soyoz et al. / Procedia Engineering 199 (2017) 1026–1031 S.Soyoz et al./ Procedia Engineering 00 (2017) 000–000
1031
Fig. 8. Deck modal frequency change Table 1. Change in Modal Frequencies Mode 1 (1st Lsym)
Before Retrofitting 0.074 Hz
During Retrofitting 0.076 Hz
After Retrofitting 0.081 Hz
2 (1st Vasym)
0.137 Hz
0.137 Hz
0.125 Hz
3 (1st Vsym)
0.159 Hz
0.154 Hz
0.149 Hz
4 (2nd Vsym)
0.217 Hz
0.215 Hz
0.201 Hz
5 (2nd Vasym)
0.276 Hz
0.262 Hz
0.243 Hz
5. Conclusion Vibration based monitoring of Bogazici Suspension Bridge during configuration change of hangers from inclined to vertical was carried out almost for one year. Results indicate that there is a clear decrease in the vertical modal frequencies of the deck. This and other findings need further analytical investigation using finite element model of the bridge. Experimental and analytical studies will eventually allow us to understand the dynamic behaviour of the Bridge in detail. Acknowledgements Authors from Departments of Civil and Earthquake Engineering of Bogazici University acknowledge the funding by Bogazici University BAP 10150 and Prof Catbas acknowledges the contribution of Tubitak 2221 project. We would also like to acknowledge the help of General Directorate of Highways staff at Bogazici Bridge References [1] S. Tezcan, M. Ipek, J. Petrovski, T. Paskalov, Forced Vibration Survey of Istanbul Bogazici Suspension Bridge, 5th European Conference on Earthquake Engineering, Istanbul, Turkey. (1975). [2] W. J.M.W. Brownjohn, A.A. Dumanoglu, R.T. Severn, A. Blakeborough, Ambient Vibration Survey of the Bosporus Suspension Bridge, Earthquake Engineering and Structural Dynamics, 18 (1989) 263-283. [3] G. M. Erdik, E. Uckan, Ambient Vibration Survey of the Bosporus Suspension Bridge, KOERI Report 89-5, Bogazici University, Istanbul, Turkey. (1989). [4] N.M. Apaydin, Earthquake Performance Assessment and Retrofit Investigations of Two Suspension Bridges in Istanbul, Soil Dynamics and Earthquake Engineering, 30 (2010) 702-710. [5] N.M. Apaydin, C. Zulfikar, E. Safak, Vibration Characteristics of Bogazici Suspension Bridge Using Structural Health Monitoring Data, 2nd Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures, Istanbul, Turkey. (2013).