A Real-Time Instrumentation

Approach for Structural Health

Monitoring of Bridges

Sarp Dinçer, Civil and Structural Engineer(M.Sc.), Teknik Destek Grubu

Eren Aydın, Technical Coordinator, Teknik Destek Grubu

Himmet Gencer, Software Developer, Teknik Destek Grubu

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Scope: This study is limited to the instrumentation part of SHM, rather

than further analysis aspects form CE point of view.

History of civil engineering is full of examples of sudden and unexpected

failures of bridges and tunnels

Çaycuma, Turkey, 2012

61 years old

Tacoma Narrows Bridge, 1940

4 months old

A Real-Time Instrumentation Approach for Structural Health Monitoring of Bridges. Proceedings of the Istanbul Bridge Conference, 2014

1.Welcome

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

2.Introduction &

Scope

At least 3 theories are still available for the collapse of Tacoma Bridge,

and neither one has been agreed upon yet

A Real-Time Instrumentation Approach for Structural Health Monitoring of Bridges. Proceedings of the Istanbul Bridge Conference, 2014

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Primary Causes of Failure for Bridges and Tunnels

BRIDGES

Fatigue

Reduction of Rigidity

due to Aging

A Real-Time Instrumentation Approach for Structural Health Monitoring of Bridges. Proceedings of the Istanbul Bridge Conference, 2014

TUNNELS

Creep

Huge Static Loads

during Lifetime

Why should we monitor these structures?

To prevent LIFE LOSS To learn more about the BEHAVIOR To prevent ECONOMIC LOSS

Either;

-We will wait for the structure to choose the time for sudden collapse (Disaster)

-Or, we will collapse it down after a certain period of time and construct a new one (Waste of time and Money)

-Or we will monitor them, and decide the best time and components to repair, maintain and rehabilitate

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

All the instrumentation proposed in this study is based on 7/24 real

time monitoring

Characteristic of Instrumentation and Sensors

STATIC DYNAMIC+A combined approach is being proposed

SensorsCabling + Wireless

Sync

Digitizer +Data

Center

Monitoring Software

Real-Time +Post

Analysis SW

Reports/ Feedbacks+Warnings

The Road to Real-Time Structural Health Monitoring

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Selecting the right combination of

instruments among a big batch

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

General Layout for the Proposed SHM Methodology

DYNAMIC PART

Based on an innovative modification of

conventional data acquisition

STATIC PART

Based on an fiber-optical solution with FBG

(fiber-bragg-grating) sensors

WHAT IS INNOVATIVE ABOUT THIS METHOD?

Combines 2 best fits for the dynamic and static

monitoring

Consolidates 2 different technologies at the

same data center, same monitoring and real-

time analysis software

Outputs a solid turn-key solution

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

0

500

1000

1500

2000

2500

3000

80 100 120 140 160

USD

/ A

XIS

PERFORMANCE (DB)

Accelerometers (Cost/Performance)

FBA

MEMS – MET

ICP / IEPE

FREQUENCY RESPONSE

BANDWIDTH

Accelerometers

Operational Modal Analysis /

Ambient Vibration

Dynamic Identity

-Conventional FBAs: best for long period signals, close to DC.

-MEMS/METs: also including force-feedback, best for 0.1 to 100 Hz signals.

-IEPE type piezo-electric: best for high frequency measurement

Noise performance

For buildings: <300-500 nano-g/√Hz

*For bridges: <10µg/√Hz

Bandwidth(at least):0.1 – 100 Hz

Range: ±2 to 3 g

Accelerometer Selection

Dynamic Instrumentation1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Dynamic Instrumentation

A general rule of thumb:

24-Bit + Simultaneous Sampling(1kHz) + >120 dB

What is proposed extra in this approach?

+ Wireless GPS Based Synchronization

for each independent node

+ Low-cost & <1 micro-second resolution

+ Directly drives ADCs

+ Digital data transfer over ethernet

+ No analog cabling

Digitizer Selection

TESTBOX™/e-QUAKE™

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Static Instrumentation

Monitors and Measures:

Deformations

Stress Levels

Position of Neutral Axis

Torsion

Tilt

Crack

Fiber Bragg Grating (FBG)Why Fiber?

Long spans

Different installation opportunities

Static measurement

Multiplexing

EMI/RFI Immunity

Cost optimization

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Overview of the Combined Approach

WHY?

Both parts are not fiber?

High cost for simultaneous sampling at dynamic speeds especially when the number of

nodes increase

Fiber accelerometers are not as efficient as low-cost MEMS-MET accelerometers

Hard to maintain a full synchronization for operational modal analysis as the no of nodes

increase

Both parts are not conventional?

FBG strain gauges are the best fit having a number of installation choices

Cost decreases as the number of nodes increase

Conventional strain gauges are not as durable as fiber sensors

Conventional strain gauges need protection and modification, which increases the cost

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Conclusion

A well-combined mixed approach has been proposed for

Real-Time structural health monitoring of bridges

Conventional, analog instrumentation solves the dynamic

monitoring, including acceleration and dynamic

identification.

This conventional dynamic part includes innovative solutions

inside such as wireless GPS based time synchronization

Fiber sensors solves the static monitoring, including

deformation, stress, neutral axis watch, torsion, tilt and crack

watch.

Data center is capable of handling both parts smoothly.

Real-time calculations and analysis is carried out by a

integrated software both separately and sometimes

considering and double checking the static and dynamic

measurements together.

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

A Real-Time Instrumentation

Approach for Structural Health

Monitoring of Bridges

Sarp Dinçer, Civil and Structural Engineer(M.Sc.), Teknik Destek Grubu

Eren Aydın, Technical Coordinator, Teknik Destek Grubu

Himmet Gencer, Software Developer, Teknik Destek Grubu

TESTBOXData Acquisition Systems

Manufacturer of Turkey

TESTARTSensor & Test

Technologies

www.testart.com.tr

Thank you.

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Tunnels

Rossio Railway Tunnel, Lisbon Portugal

For tunnels, it is possible to monitor deformation and convergence by fiber optic sensors.

A solid case study for this solution was carried out by Barbosa et al. in 2009 for Rossio train tunnel in Lisbon, Portugal.

The monitoring system was a complete solution that comprises measurements of strain and temperature with more than 850 fiber Bragg grating sensors, data acquisition, processing, storage and easy access through a web platform.

The used method for convergence monitoring (MEMCOT) makes it possible to determine tunnel convergences based on strain measurements around the tunnel contour.

An optoelectronic measurement unit and optic switch are deployed at the entrance of the tunnel and remotely connected to a server that saves and displays information to authorized users in web interface

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Recent Solid Experiences From Buildings

EKSEN DOĞU-BATI KUZEY-GÜNEY

1.MOD

FREKANS

(Hz)

HAKİM

PERİYOT

(sn)

1.MOD

FREKANS

(Hz)

HAKİM

PERİYOT

(sn)

REF BİNASI 1,80 0,55 1,56 0,64

TEST BİNASI 1,38 0,73 1,48 0,68

DEĞİŞİMİN

ANLAMI

TEST BİNASINDA CİDDİ

RİJİTLİK KAYBI /

YUMUŞAMA

TEST BİNASINDA RİJİTLİK

KAYBI / YUMUŞAMA

DEĞİŞİM ORANI

(%)33 6

Kuzey-Güney

Doğu-Batı

REF

TEST

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Recent Solid Experiences From Buildings

Doğu-Batı

Kuzey-Güney

EKSEN DOĞU-BATI KUZEY-GÜNEY

1.MOD (Hz) 2.MOD (Hz) 1.MOD (Hz) 2.MOD (Hz)

DURUM 1 1.824 5.608 1.562 5.210

DURUM 2 1.808 5.551 1.554 5.161

DURUM 3 1.792 5.480 1.550 5.126

EKSEN DOĞU-BATI KUZEY-GÜNEY

1.MOD

% Artış

2.MOD

% Artış

1.MOD

% Artış

2.MOD

% Artış

DURUM 1-2 0.9 1.1 0.6 1

DURUM 2-3 0.9 1.1 0.2 0.5

DURUM 1-3 1.8 2.2 0.8 1.6

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You

Oversampling Dynamic Range and Effective Resolution

Her 1 bit çözünürlük artışı için sinyal, 4’ün o kadar kuvveti kadar

fazla örneklenmelidir(oversample)

Örnek: 19 bit @ 4 kHz bir sistem ? @50Hz

4kHz=4w. 50 Hz 80=4w w=3.2 bit

Etkili çözünürlük(ENOB)= 19 + 3,2 = 22 bit @ 50Hz

200 Hz’de, 128 dB dinamik aralığa sahip bir veri toplama

sistemine ihtiyaç varsa:

19 bit @ 4 kHz bir sistem bunu sağlayabilir mi? 19bit→116 dB

128-116= 12 dB artış bekleniyor,

Her fazladan etkili 1 bit, 6 dB artışa denk geliyor,

12 / 6 = 2 bit artış?

4kHz=4w. 200 Hz 4w=20 w>2 bit,

Bu sistemle 200Hz’de en az 2 bit, (12 dB) artış sağlanabilir.

EĞER DOĞRU OVERSAMPLING VE DOWNSAMPLING TEKNİKLERİ

KULLANILIRSA

fos= 4w.fsw:istenilen bit artışı,

fos: fazla örnekleme frekansı,

fs: daha yüksek çözünürlüklü elde

edilen örnekleme frekansı

SNR(dB) = (6,02 . ENOB) + 1,76

SNR: sinyal gürültü oranı

ENOB: etkili çözünürlük

BİT dB O/S

1.Welcome

2.Introduction &

Scope

3.Why to Monitor?

4.7/24 Real-Time

Monitoring

5.Solution

6.General Layout

7.Dynamic Part

8.Static Part

9.Overview

10.Conclusion

11.Thank You