Monitoring Static and Dynamic Characteristic of Tall Building
Monitoring Static and Dynamic Characteristic of Tall Building Using GPS Virtual Reference Station and Seismic Sensor Data Huang Liping (Dr) , NTU Kusnowidjaja Megawati (Assoc Prof), NTU Tor Yam Khoon (Assoc Prof), NTU Victor Khoo Hock Soon (Dr), SLA Gerry Ong, GPSLands (S) Pte Ltd Teo Swee Tiong, GPSLands (S) Pte Ltd presented by TOR, Yam Khoon Assoc. Prof. School or Civil & Environmental Engineering Map Asia 2009 20 August 2009
Contents • • Si. RENT GPS and Accelerometer Setup Natural Frequency of Building Results and Analysis – Accelerometer – 1 -Hz GPS – 10 -Hz GPS • Conclusions
Singapore Satellite Positioning Reference Network (Si. Re. NT )
SKEP-Keppel Club SNTU-NTU SSEKSenoko SLOYLoyang SNYPNanyang Poly
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 VRS position is established NMEA Source: Trimble
VRS Data Flow Server uses VRS position to create corrected RTCM real-time data VRS Rover surveys as in normal RTK – but getting VRS data as if from a nearby reference station RTCM NMEA Source: Trimble
GPS and Accelerometer Setup
Location of GPS antennas 20. 629 m 29. 211 m 20. 445 m
Location of accelerometer Y – B e d o e od m accelerometer X – A m
Combined sensor setup North Y – B 5700 e od m Accelerometer R 702 R 701 X – A m e d o
High Rise building monitoring GPS receivers mounted on rooftop of the building. weatherproof housing for receivers and device servers
5700 (North) R 702 (West) R 701 (South) System Set-up for Building Movement Detection & Monitoring System RG 213 RG 58 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 192. 168. 1. 21 (63431) 192. 168. 1. 22 (63432) 192. 168. 1. 23 (63433) Si. Re. NT RS 232 RJ 45 Real-Time Network Correction & Post-Process RINEX Data Internet Port 1 – RT 17 Port 2 – Configuration Port 3 – NMEA/CMR Processing Server
Sensors located at basement and 65 th storey Two QA 700 Q-Flex accelerometers sensors with bi-axial horizontal direction are th th located on the 65 storey and basement. Data collection continues from 6 April to th 13 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 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 • 1 st , 2 nd , 3 rd , 4 th , etc. • Lowest Frequency is 1 st Mode • Frequency increases with each subsequent mode of vibration
Modes of Vibration 1 st 2 nd 3 rd
Natural Frequency and Building 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 on the NEW Uniform Building Code (1997 UBC) 3/4 0. 035* (280*3. 28084) T= = 5. 84 sec F = 1/5. 84 = 0. 1712 Hz Calculating Period Based on the OLD UBC Period = 0. 1 x 66 = 6. 6 sec F = 1/6. 6 = 0. 1515 Hz
Results and Analysis
Modal frequency for Republic Plaza (using available data from Jan. 2007 to Dec. 2007) A-mode frequency(Hz) B-mode frequency(Hz) T-mode frequency(Hz) A 1 0. 1709 B 1 0. 1953 T 1 0. 5127 A 2 0. 6592 B 2 0. 708 T 2 1. 1963 A 3 1. 4404 B 3 1. 6357 T 3 2. 124 A 4 2. 2705 B 4 2. 7832 T 4 3. 2959 Modal frequency for Republic Plaza (using GPS R 701 – VRS Solution, East, 26 May 2009 ) – 10 Hz A-mode frequency(Hz) B-mode frequency(Hz) T-mode frequency(Hz) A 1 0. 176 B 1 0. 234 T 1 0. 469 A 2 0. 625 B 2 0. 818 T 2 1. 093 A 3 1. 406 B 3 1. 641 T 3 1. 956 A 4 2. 210 B 4 2. 734 T 4 3. 203
Accelerometer
Seismic sensor data and corresponding power spectrum analysis with high-pass filter from 0. 1 Hz (00: 00 -00: 59 9 April, 2009) – 100 Hz 0. 1953 0. 1709 0. 708 1. 6357 2. 2705 2. 7832
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. 2705 2. 7832
IMF and Power Spectrum Analysis of accelerometer data IMFs Corresponding power spectrum analysis 1. 6357 1. 4404 2. 2705 0. 708 0. 6592 0. 1953 0. 1709
1 Hz GPS
Displacements of R 701 (VRS Solution) 27 May 2009 – 1 Hz East North
Displacements of R 702 (VRS Solution) 27 May 2009 – 1 Hz (Rover RTK) East North
Displacements of R 701 (Non-VRS Solution) 28 May 2009 – 1 Hz (Rover RTK) East North
Displacements of R 702 (Non-VRS Solution) 28 May 2009 – 1 Hz (Rover RTK) East North
Power Spectrum of R 701 (VRS Solution) 27 May 2009 – 1 Hz (Rover RTK) East North
Power Spectrum of R 701 (Non-VRS Solution) 28 May 2009 – 1 Hz (Rover RTK) East North
Power Spectrum of a week of data (05/04/2009 -12/04/2009) for R 701 – 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 highrise buildings.
10 Hz GPS
Displacements of R 701 & R 702 (VRS Solution) 26 May 2009 – 10 Hz (Rover RTK) East
Displacements of R 701 & R 702 (VRS Solution) 26 May 2009 – 10 Hz (Rover RTK) North
Displacements of R 701 & R 702 (Non-VRS Solution) 27 May 2009 – 10 Hz (Rover RTK) East
Displacements of R 701 & R 702 (Non-VRS Solution) 27 May 2009 – 10 Hz (Rover RTK) North
Displacements of R 701 & R 702 (Non-VRS Solution) 27 May 2009 – 10 Hz (Rover RTK) North
Power Spectrum Analysis of R 701 & R 702 (VRS Solution) 26 May 2009 – 10 Hz (Rover RTK) East
Power Spectrum Analysis of R 701 & R 702 (VRS Solution) 26 May 2009 – 10 Hz (Rover RTK) North
EMD (Empirical Mode Decomposition) of R 701 RPB (VRS Solution) East 26 May 2009 – 10 Hz (Rover RTK) Corresponding frequencies components IMF (Intrinsic Mode Function) B 4 B 2 A 2 B 3 A 4 A 3
EMD (Empirical Mode Decomposition) of R 701 RPB (VRS Solution) East 26 May 2009 – 10 Hz (Rover RTK) Corresponding frequencies components IMF (Intrinsic Mode Function) B 1 A 1
Power Spectrum Analysis – 1 Hz GPS data • If sampling R 701 (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 • VRS solution is acceptable
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