Monitoring Static and Dynamic Characteristic of Tall Building Using GPS Virtual Reference Station and Seismic Sensor Data presented by TOR, Yam Khoon Assoc. Prof. School or Civil & Environmental Engineering Map Asia 2009 20 August 2009 Huang Liping (Dr) , NTU Victor Khoo Hock Soon (Dr), SLA Kusnowidjaja Megawati (Assoc Prof), NTU Gerry Ong, GPSLands (S) Pte Ltd Tor Yam Khoon (Assoc Prof), NTU Teo Swee Tiong, GPSLands (S) Pte Ltd
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Monitoring Static and Dynamic Characteristic of Tall Building Using GPS Virtual Reference Station and Seismic Sensor Data presented by TOR, Yam Khoon Assoc.
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Monitoring Static and Dynamic Characteristic of Tall Building Using GPS Virtual Reference Station and Seismic Sensor Data
presented by
TOR, Yam KhoonAssoc. Prof.School or Civil & Environmental Engineering
Apparent Advantages of Virtual Reference System (VRS) Network
• Significantly reduces systematic errors (ionospheric and tropospheric delay)
• Extended operating range with improved initialization and accuracy
• Increased productivity
• Less investment for the user
• Eliminates needs to establish local reference station
Source: Trimble
VRS Data Flow
Reference station data
streams back to the
server via leased lines
or LAN/WAN
Source: Trimble
VRS Data Flow
Roving receiver sends its
position back to the server
NMEANMEA
VRS position is
established
VRSVRS
Source: Trimble
VRS Data Flow
VRSVRS
NMEANMEA
Server uses VRS position
to create corrected
RTCM real-time data
RTCMRTCM
Rover surveys as in
normal RTK – but
getting VRS data as if from a nearby reference
station
Source: Trimble
GPS and Accelerometer Setup
20.629m
20.445m
29.211m
Location of GPS antennas
Location of accelerometer
X – A m
ode
Y – B mode
accelerometer
Combined sensor setup
5700
R701
R702
North
Accelerometer
X – A m
odeY – B mode
High Rise building monitoring
GPS receivers mounted on rooftop
of the building.
weatherproof housing
for receivers and device
servers
192.168.1.21
(63431)
5700
(North)
5700
(North)
R701
(South)
R701
(South)
R702
(West)
R702
(West)
192.168.1.22
(63432)
192.168.1.23
(63433)
Port 1 – 9011
Port 2 – 9012
Port 3 – 9013
Port 1 – 9021
Port 2 – 9022
Port 3 – 9023
Port 1 – 9031
Port 2 – 9032
Port 3 – 9033
RG213
RG58
RS232
RJ45
Port 1 – RT17
Port 2 – Configuration
Port 3 – NMEA/CMR
Internet
Processing
Server
Processing
Server
SiReNTSiReNT
Real-Time Network
Correction
&
Post-Process RINEX Data
System Set-up for
Building
Movement Detection &
Monitoring System
System Set-up for
Building
Movement Detection &
Monitoring System
Sensors located at basement and 65th storey
Two QA700 Q-Flex accelerometers sensors with bi-axial horizontal direction are located on the
65th
storey and basement. Data collection continues from 6th
April to 13th
April at sampling
frequency at 100 Hz. Totally one week’s data was collected.
GPS Vs Accelerometer
• The purpose of the accelerometer system is to capture structural response due to wind loading and during occasional events such as long-distant earthquake
• The seismic sensor system can only record the dynamic performance of the structure instead of tracking dynamic and static performance at the same time as GPS
Differential processing (for displacement data by GPS)
Differential processing (for displacement data by GPS)
Velocity
Velocity differential from GPS data
Velocity integrated from seismic sensor data
Displacement
GPS data
Displacement integrated from seismic sensor data
Natural Frequency of Building
Natural Frequency
• When a body freely executes a to-and fro motion about some fixed point it is in oscillation
• The time required to make one full oscillation is the natural frequency of the body in seconds
Modes of Vibration
• Structures can Have More than one Mode of Vibration
• 1st , 2nd , 3rd , 4th , etc.• Lowest Frequency is 1st Mode• Frequency increases with each subsequent mode
of vibration
Modes of Vibration
1st 2nd 3rd
Natural Frequency andBuilding Design
• Design Buildings OUTSIDE their Natural Frequency … Otherwise they are Subject to Collapse
• General Rule …– Short Buildings are Stiff and Have High Natural
Frequencies– Tall Buildings have Low Natural Frequencies
Calculating Period Based onthe NEW Uniform Building Code (1997 UBC)
Seismic sensor data and corresponding power spectrum analysis with high-pass filter from 0.1 Hz (00:00:00-00:59:59 9 April, 2009) – 100Hz
0.1709
0.1953
2.78322.27051.6357
0.708
Empirical mode decomposition (EMD)
• EMD is a method of breaking down a signal without leaving the time domain
• Using the EMD method, any complicated data set can be decomposed into a finite and often small number of components, which is a collection of Intrinsic mode functions (IMF).
• An IMF represents a generally simple oscillatory mode as a counterpart to the simple harmonic function.
IMF and Power Spectrum Analysis of accelerometer data
IMFs Corresponding power spectrum analysis
2.27052.7832
IMF and Power Spectrum Analysis of accelerometer data
IMFs Corresponding power spectrum analysis
2.27051.6357
1.4404
0.708
0.6592
0.1709
0.1953
1 Hz GPS
Displacements of R701 (VRS Solution)27 May 2009 – 1 Hz
North
East
Displacements of R702 (VRS Solution) 27 May 2009 – 1 Hz (Rover RTK)
North
East
Displacements of R701 (Non-VRS Solution) 28 May 2009 – 1 Hz (Rover RTK)
North
East
Displacements of R702 (Non-VRS Solution) 28 May 2009 – 1 Hz (Rover RTK)
North
East
Power Spectrum of R701 (VRS Solution) 27 May 2009 – 1 Hz (Rover RTK)
North
East
Power Spectrum of R701 (Non-VRS Solution) 28 May 2009 – 1 Hz (Rover RTK)
North
East
Power Spectrum of a week of data (05/04/2009-12/04/2009) for R701 – 1 Hz (Rover RTK)
Observation
• The nature frequency of 0.1758 Hz is dominant for analysis of one week’s data. Comparing to the nature frequency measured by accelerometer 0.1709 Hz, 0.0049 Hz differences exist. Though GPS monitoring of displacement (using 1 Hz data) is somewhat noisy, it can record natural dynamic characteristic of slender engineering like high-rise buildings.
10 Hz GPS
Displacements of R701 & R702 (VRS Solution) 26 May 2009 – 10 Hz (Rover RTK)
East
Displacements of R701 & R702 (VRS Solution) 26 May 2009 – 10 Hz (Rover RTK)
North
Displacements of R701 & R702 (Non-VRS Solution) 27 May 2009 – 10 Hz (Rover RTK)
East
Displacements of R701 & R702 (Non-VRS Solution) 27 May 2009 – 10 Hz (Rover RTK)
North
Displacements of R701 & R702 (Non-VRS Solution) 27 May 2009 – 10 Hz (Rover RTK)
North
Power Spectrum Analysis of R701 & R702 (VRS Solution) 26 May 2009 – 10 Hz (Rover RTK)
East
Power Spectrum Analysis of R701 & R702 (VRS Solution) 26 May 2009 – 10 Hz (Rover RTK)
North
EMD (Empirical Mode Decomposition) of R701 RPB (VRS Solution) East26 May 2009 – 10 Hz (Rover RTK)
IMF (Intrinsic Mode Function) Corresponding frequencies components
A2
B2 B3 A4A3
B4
EMD (Empirical Mode Decomposition) of R701 RPB (VRS Solution) East26 May 2009 – 10 Hz (Rover RTK)
• If sampling R701 (VRS Solution) - North, 26 May 2009 data at 1 Hz, the first mode of the structure is at 0.1836 Hz.
Conclusions
• Accelerometer is capable to measure sway vibration response, but cannot detect the permanent changes in buildings induced by wind or due to environment temperature changes. GPS system data can give information for dynamic + static performance
• If only minor tremors occurred like under ambient vibration condition, the amplitude of response displacement might be covered by GPS noise. While GPS data may show possibility in higher amplitude acceleration induced by wind or long-distance earthquake
Consclusion
• 10-Hz GPS is better in detecting the natural frequency of the tall and slender building than the 1-Hz GPS