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Real Time
Monitoring of
MBF Structure
Dr G H Tan
Tritech Group
SysEng (S) Pte Ltd
TriTech
Marina Bay
Sands Towers
Real Time Structural Health Monitoring (SHM)
•Sensors are measured and processed every 10 minutes and
available in the secured website using Machine to Machine
Technologies (M2M)
•300 MEMs Tilt sensors for structure movements
•400 VW Strain Gages and 400 Temperatures for cast-in, Post-
tensioning and strut monitoring
•System handles 158,400 sensor readings per day
•Monitoring Period was 12 months during construction
Confidential and Copyright
Confidential and Copyright
Real Time Safety Monitoring for Deep Excavation
Structural Health Monitoring system to continuously
monitoring of Tunnels
System used:-
•Real Time Tunnel Monitoring & Alert system used
since 2002
•Tilt sensors are used to monitor the track sleepers
•Uses proven Leica Automatic Total Station Technology
•Prisms are measured, data are processed and made
available in the secured website using Machine to
Machine Technologies (M2M)
Track Tilt sensor
Prism
locations
Real Time Automatic Tunnel Monitoring System
Confidential and Copyright
Real Time
Structural Monitoring
Quasi-Static
Dynamic
What is Real Time
Monitoring & Alert
System ?
What is actual
Real Time ?
Is it continuous monitoring ? Then what is
continuous then ?
Is it Real Time Data logging only ? Data
Logging is ONLY one basic component for Real
Time Monitoring and Alert system
If characteristics move in days, then monitoring
every hour is real time
If characteristics move in hours, then monitoring
every minute is real time
This was the system Deployed for Real Time Monitoring & Alert
System is Actual Only Real Time Data Logging !
Upload 0000 hrs
Email Alert
only @
0000 hrs !
next day
Walers buckle More Walers buckle
Real Time Monitoring
& Alert System used
in many projects
since 2001
SysEng Real Time Monitoring System SetupLogger #1
Logger #2
Logger #n
GPRS
Network
GPRS Link
GPRS GateWay
GPRS Link
GP
RS
Lin
k
Data Processor and Alert
for Logger #1
Data Processor and Alert
for Logger #2
Data Processor and Alert
for Logger #n
Data Backup
System
Supervisor
SMS
Server
Web and eMail
Server
Construction
Site
SysEng
Server Room
WAN
and
Real tilme Data
Wireless Network
SMSuser HP #1
User HP #2 User HP #n
SysEng Real Time
Monitoring System
User
Uer #1 User #2 User#n
Dial UPADSL
ADSL
http:\\www.syseng-m2m.com
Track Records
Real Time Structural
Monitoring System
(Pasir Panjang Semi
Expressway)
Embedded & Surface
Bonded Sensors
Embedded VW Strain Gage
2001 to 2004
LTA Pasir Panjang C3223
Bridge Instrumentation at
Kicker, Column and Box
Girder
2006 with surface
bonded sensors
during C856 project
2007 Pasir Panjang Semi Expressway
Pier Monitoring System
Total of 11PiersPier Structure
movement detected,
caused by nearby
construction work 1st 2nd
Real Time Structural Monitoring System
(Hong Kong North East Tower in 2001)
High Rise Building during Construction
Construction
Phases of a
420 m High
Tower Block in
HK
Configuration
Level 33
RS485
Network
Level 53
RS485
Network
Level 65
RS485
Network
2.4 GHz
Highway
Central Data
Logging Station
SMS Alert
System
Strain Gages and Displacement Sensors
Real Time Structural Monitoring System
(Republic Plaza)
High Rise Building during Post-Construction
Long Term Building Dynamics
Monitoring at 280 m Republic Plaza
since 1995
Remote Monitoring of the 280m
High Republic Plaza
Measures the Wind Load and Seismic
conditions experienced by the Building
NTU conducts the Full Scale Research while
SysEng (S) designs and install the
Instrumentation
The system operates automatically since 1995
The system can be controlled remotely and
measured data are via modems
Transducers at Republic Plaza
(Top) Ultra sonic
Anemometer to
measure Wind
Direction & Speed
(Top & Bottom)
Servo
Accelerometers to
measure vibrations
GPS receivers to
measure
displacements
Ultrasonic Anemometer
Mounted on Top of
building
No moving parts
Reliable
Lightning Protection
Robust for out door
continuous use
Dual Axes Balanced DC Servo
Accelerometer Module
Real Time Structural Monitoring System
(Helix Bridge)
Bridge Monitoring
Post-Construction
URA The Helix at Marina Bay
Elevation Layout
Dynamic Shaker Servo Accelerometer
Real Time Structural
Monitoring System
(MBS Hotel Towers)
Cast-in VW Strain Gage
•To measure the vertical
force from the
superstructure
Welded VW Strain Gage
•To measure the
tension/compression force on
the support beam between the
vertical and slope core
x
L
x = Lsinθ
Where L is floor
height
D
Ln-2
Ln-1
Ln
L1
L3
L2
Tilt meter
Displacement Sensor
Total Lateral Displacement at
level n-> Xi = D + ∑ Li sin θi
D
Individual floor level
lateral displacement can
be determined by using
•Displacement sensor as
the referencing datum
•Accumulated lateral
movement resolved from
tilting angle detected by
tilt meter
X i
X i
X i
X i
X i
X i
D
Location of
•Tilt Meter
•Displacement
sensor
Challenges
in Operating and
Maintaining Systems
Real Time
Monitoring & Alert is
Analyzing the data
immediately into
information for the user
to take informed decision
Systematic data management is required to
avoid information overload and condense huge
information into information the human user can
handle
Simplify the human interface for easy
interpretation and de-skilling of decision
operations
Real Time Continuous Monitoring by Computers
need the same corresponding Real Time
Continuous Analysis by computers also !
Real Time Monitoring & Alert System
gives SMS Alerts within 10
minutes,hence earlier reaction time for
crisis management
SMS
Alert
Important data
flow path
Quality & Reliability
of
Sensor Data
Sensor
Signal
Conditioner
Data
Logger
High Electro Magnetic
Interference or Unwanted signal
sources from Motors, Arc
welding Equipment, Heaters,
Inverters, etc
Digital Signal
with 1.10 valueAnalogue
Signals
Use of a Fast Fourier
Transform (FFT)
Spectrum Analyzer to
check the Signal to
Noise Ratio to verify
Quality of Signal
presented to the ADC
Readout gives 1.1value
= 1.05(Sensor) + 0.05(Noise)?
= 0.9 (Sensor) + 0.2 (Noise) ?
= 0.5 (Sensor) + 0.6 (Noise) ?
EMI Noise affecting the sensor readings
Under Ideal condition, the Data Quality is
maintained even if 1000 m cables are used
Site conditions generate EMI Noise due to Arc Welding,
Power Generators and High Current AC current wires
inducing noise into sensor wires due to cross coupling.
Cables with improper shielding configuration, ungrounded
shielded cable ends, exposed cable joints can corrupt
sensor readings
But the Reality is that a site condition is very different
Non Noise site ~ 500m while Noisy site ~ 200m
Portable
EMI Meter
to pin-
point the
source
Same Data Logger but monitoring different sensors via
Multiplexers showing EMI noise affecting readings over days
EMI Noise
Time scale in days
Time scale in days
Real Time scale in minutes
Good Engineering Practices
Site Layout Design Consideration
Consideration factors
Maximum signal cable length
Reduce noise pickup possibility
Cable installation
Avoid noise source
Avoid wielding cable and power generator cable crossing
Max numbers of channels per logger
Cluster design
Easy to view sensors info at Real Time monitoring & Alert System
160.86m
24m
24m
Depth =27m
A B
C
D
Max distance
A - ~ 60meter
B - ~ 60meter
C - ~ 45meter
D - ~ 40meter
Cluster design
-Easy to install and Maintain
-Keep out from noise source
-Keep out from working place
-Avoid cable crossing power cables
Sensors are precision devices
•Resolution & Accuracy
•Handling & Storage from office to
site
•Mounting Sensor in right location
where it is sensitive to movements
and in-sensitive to noise
•Sensor to Cable link water
proofing
•Lightning protection to avoid
sensor intermittent failures
