Research on technical solution of displacement and deformation monitoring of high-Rise buildings in real time

 Journal of Mining and Earth Sciences Vol. 60, Issue 3 (2020) 75 - 87 75 
Research on technical solution of displacement and deformation monitoring of high-rise buildings in real time Khai Cong Pham * 
Faculty of Geomatics and Land administration, Hanoi University of Mining and Geology, Vietnam 
 ARTICLE INFO ABSTRACT 
Article history: Received 01st Feb. 2020 Accepted 20th May 2020 Available online 30th June 2020 
This article presents a technical solution of displacement and deformation 
monitoring in real-time based on GNSS CORS technology. The components 
and principles of operation of the monitoring system for displacement and 
deformation have been designed and established. The continuous 
operation reference station (CORS) with Net S8+ receiver was used to 
correct position for monitoring station in the RTCM format. A device for 
receiving and transmitting data from the monitoring station to the server 
has been designed and developed. NMEA messages have been decoded 
and filtered through three steps using our self-developed software which 
improves the accuracy of the monitoring results. The results of monitoring 
of displacement and deformation of An Binh high-rise building (in Hanoi) 
show that the developed equipment system can monitor displacement 
horizontally to 3 mm and vertical displacement to 5 mm. Copyright © 2020 Hanoi University of Mining and Geology. All rights reserved. 
Keywords: Continuous Monitoring, Continuously Operating Reference Station (CORS), Displacement and Deformation, Global Navigation Satellite System (GNSS), Net S8+ receiver, Real Time. 
1. Introduction The industrialization and urbanization processes have occured fast during the last several decades which lead to industrial and civil construction projects that are getting bigger and higher. However, the construction works on the ground are often displaced and deformed due to the impact of many different factors, therefore, monitoring displacement and deformation of 
construction works is an important task. The real time identification of the deformation and displacement of buildings can reduce the risk of accidents that can happen to people and avoid financial losses (Bochen Zhang et al., 2018; Deng Hui Wang et al., 2017). Up to now in Vietnam most of the deformation and displacement monitoring works are mainly periodically carried out by traditional measuring devices such as level, theodolite, total electronic station or by GPS technology. It is difficult to monitor continuously changing deformation and displacement in real time by using this technology and equipments. The deformation and displacement surveying needs to be automatically and 
_____________________ 
*Corresponding author 
E-mail: phamcongkhai@humg.edu.vn DOI: 10.46326/JMES.2020.61(3).09 
76 Khai Cong Pham/Journal of Mining and Earth Sciences 60 (3), 75 - 87 continuously carried out in real time due to the rapid development of new technology. The deformation and displacement surveying of high-rise buildings has been effectively studied by GNSS technology (N. Quesada-Olmo et al., 2018; Wan Abdul Aziz Wan Mohd Akib et al., 2012). Deflection and horizontal displacement of bridges can be determined by using GNSS technology (Jiayong Yu et al., 2014). The GNSS system currently allows the continuous reception of satellite signals using real-time RTK dynamic measurement technology with high accuracy. The advantages of GNSS technology are to provide 3D data in real time, operate continuously with different weather conditions, the position with high precision, therefore, this technology has been applied to survey displacement and deformation of bridges effectively (Ruijie Xi et al., 2018). The GNSS technology monitoring system has been widely and effectively applied in many countries over the world. However, these systems all have their own hardware, software and high cost. Therefore, the idea of developing a system for real time continuously monitoring deformation transformation based on GNSS/CORS technology has been proposed. From the working principle and data transmission mechanism of CORS station with Net S8+ receiver, this article describes the development of a device to receive and transmit the corrected data from the user station (User) located at the monitoring position to master station (Server). All measurements from the user station are automatically and continuously sent to the master station. Here software (Server GNSS CORS WDM, GNSS CORS WDM (Pham Cong Khai et al., 2019, Pham Cong Khai et al., 2020) have been designed to handle the measured data received from the user at the monitoring point to produce the results of the instantaneous displacement and deformation of the construction works. To test the accuracy and stability of the system, a dedicated device has been designed and assembled. The results of experiments show that the monitoring system works properly, stably, continuously 24/7 and can monitor the deformation and displacement of the construction works (An Binh high-rise building) from 3 mm upwards. 
2. General principles of deformation and 
displacement monitoring work The monitoring of deformation and displacement of construction works is the essential determination of its position change in space over a period of time. The equation for calculating displacement and deformation of construction works is shown in the following formula (Hepi Hapsari Handayani et al., 2015). dp = R’p - Rp = dp (Xp, Yp, Hp, t) (1) Where: Rp - position of P point at time t = 0 (before deformation); R'p - position of P point at time t > 0 (after deformation). The deformation and displacement quantity in formula (1) is defined in 4-dimensional space, including 3 dimensions according to component coordinates X, Y, H, and the fourth one is time t. The deformation along each coordinate axe is determined by the following formulas: - Deformation along X: Dx = Xi (t + 1) - Xi (t) (2) - Deformation along Y: Dy = Yi (t + 1)  ... by OY axis: Qy = Yi + 1 - Yi = 580383.4861 - 580383.4816 = 0.0045 m -Complete translation: 2YQ2XQQ = 20045.020471.0 = 0.0473 m = 47.3 mm -Vertical displacement:  = Hi + 1 - Hi = 23.651 - 23.690 = 39 mm Table 1 displays the horizontal and vertical displacement values determined by monitoring equipment and directly measured by a steel ruler mounted on the monitoring mark, the maximum horizontal displacement is 2.3 mm and the minimum is 1.5 mm. The maximum vertical displacement is 4.2mm and the minimum is 3.5 mm. 
7.3. Experimental monitoring high-rise 
buildings Using the equipment system that has been studied and developed (7.1, 7.2 sections), the monitoring experiments are conducted at the An Binh high-rise building in Hanoi, Vietnam. The building has 24 storeys, 1 basement and 3 floors of commercial services. On the roof of the building, there are 04 corner observation stations with 4 Rover numbered Rover-01, Rover-02, Rover-03, and Rover-04 (Figure 7). CORS station named CORS-N001 is used for monitoring which is built on the campus of Hanoi University of Mining and Geology, 2km away from the building (Figure 8). 
Figure 6. GNGGA data according to NMEA 0183 format standard 
 Khai Cong Pham/Journal of Mining and Earth Sciences 60 (3), 75 - 87 83 
After installing monitoring stations on the roof of the building, monitoring is automatically performed. Data at the monitoring stations were continuously sent to the server in the NMEA standard format every second. The data is saved to the server by the default path and file name. 
Figure 7. Experimental monitoring high-rise buildings. 
Number of 
Observation 
Horizontal displacement (mm) Vertical displacement (mm) 
Measured 
by a steel 
ruler 
Observed 
 by CMSS 
equipment 
Observed 
– 
Measured 
Measured 
by a steel 
ruler 
Observed 
 by CMSS 
equipment 
Observed 
 - 
Measured 
1 45 47.3 2.3 35 39.0 4.0 
2 50 51.5 1.5 45 49.2 4.2 
3 55 53.2 1.8 55 58.5 3.5 
4 60 57.8 2.2 65 68.7 3.7 
Table 1. Evaluation of accuracy of horizontal and vertical displacement monitoring results. 
Figure 8. Installation of CORS N001 station system at Hanoi University of Mining and Geology. 
84 Khai Cong Pham/Journal of Mining and Earth Sciences 60 (3), 75 - 87 
The data of each day is saved to a file, the measurement message collected at the monitoring station is sent to the NMEA-0183 standard format. Figure 9 shows a piece of data collected at An Binh building monitoring station. Monitoring is continuously carried out 24/7 within 3 months from 2nd August to 5th November 2018. Processing and analyzing data, determination on of deformation and displacement quantities, and evaluation of the stability of the observation building are carried out through the following steps: 1. Check the integrity of the messages in the GGA format in the data file. 2. Filter out messages whose coordinates have been fixed. 3. Filter out the messages which have the smallest positional uncertainties. 4. Convert the coordinates of the monitoring station to the WGS84 coordinate system. 5. Transform WGS84 coordinates to VN2000 coordinate system. 
6. From the coordinates of the monitoring point in the VN2000 coordinate system, the average of which in every hour will give one position. Comparing coordinates between different time periods will determine the horizontal and vertical displacement of the monitoring points. Based on the displacement of the monitoring stations, the stability of the building will be assessed. Results of the processing of monitored data are calculated by a self-developed software and presented in Table 2. After processing and determining the coordinates of the monitoring station the average daily coordinates for the building is calculated (step 6) and presented in Table 3. The displacements in Table 9 obtained during the 1-month observation period show that the differences in coordinates, distances, and height are smaller than their error, therefore, it can be concluded that An Binh building is stable without deformation during that time. 
$GPGGA,170000.000,2104.4617281,N,10545.8333509,E,4,13,0.8,10.451,M,-24.900,M,,0000*4C $GPGLL,2104.4617281,N,10545.8333509,E,170000.000,A,R*46 $GPGSA,A,3,27,07,23,09,11,18,08,,,,,,1.8,0.8,1.6*3F $GLGSA,A,3,78,77,88,87,81,68,,,,,,,1.8,0.8,1.6*2F $GPGSV,4,1,14,08,79,009,55,41,54,229,50,23,51,222,51,09,50,267,52*75 $GPGSV,4,2,14,27,46,033,49,11,41,179,48,42,40,114,44,18,32,151,46*7F $GPGSV,4,3,14,07,29,326,35,04,28,036,26,16,20,050,,01,16,174,26*79 $GPGSV,4,4,14,26,04,070,,28,03,267,*71 $GLGSV,3,1,09,88,66,146,45,87,47,044,47,77,40,039,38,78,27,338,42*62 $GLGSV,3,1,09,88,66,146,45,87,47,044,47,77,40,039,38,78,27,338,42*62 $GLGSV,3,2,09,81,24,190,42,67,17,229,30,68,17,284,40,76,10,097,23*6C $GLGSV,3,3,09,79,01,310,*51 $GPRMC,170000.000,A,2104.4617281,N,10545.8333509,E,000.00,00 0.00,311018,,,R*7B $GPVTG,000.00,T,,M,000.00,N,000.00,K,R*2E $GPZDA,170000.000,31,10,2018,00,00*58 $GPGST,170000.000,0.005,0.003,0.002,86.5,0.002,0.003,0.004*5B $PSTI,030,170000.000,A,2104.4617281,N,10545.8333509,E,10.451,-0.01,0.00,0.07,311018,R,1.0,10.0*2B $PSTI,032,170000.000,311018,A,R,-996.703,288.763,-17.371,1037.836,286.16,,,,,*1E $PSTI,033,170000.000,311018,1,R,0,G1,0,0,R1,0,0,G2,0,0,R2,0,0,,,,*6F $PSTI,033,170000.000,311018,1,B,0,G1,0,0,R1,0,0,G2,0,0,R2,0,0,,,,*7F $GPGGA,170001.000,2104.4617324,N,10545.8333456,E,4,13,0.8,10.420,M,-24.900,M,,0000*4E $GPGGA,170001.000,2104.4617324,N,10545.8333456,E,4,13,0.8,10.420,M,-24.900,M,,0000*4E .......................................................................................................................................................................................................... 
Figure 9. A section of monitoring data of An Binh high-rise building. 
 Khai Cong Pham/Journal of Mining and Earth Sciences 60 (3), 75 - 87 85 
8. Conclusion This work has focused on solving the problem of continuous monitoring deformation and displacement using GNSS/CORS technology. A diagram of the continuous monitoring system has been set up, including the CORS station system and CMSS monitoring station. The message types of the GNSS data structure have been successfully studied and decoded including NMEA format messages sent from the host monitoring station to the server of the CORS station. 
A GNSS data transmission system has been designed to develop both hardware and software that can in real time, continuously and automatically monitor deformation and displacement of construction works. The developed system automatically works well, stably, and guarantees instantaneous transmission of data from the monitoring station to the host computer. GNSS data processing software designed and developed allows for processing data and immediately determining the deformation and displacement of construction works. The system 
No B 
o  
L 
o  
H 
(m) 
X 
(m) 
Y 
(m) 
h 
(m) 
1 21 4 11.158440 105 46 38.154462 68.407 2330873.187 580572.482 93.469 
2 21 4 11.158470 105 46 38.154516 68.410 2330873.188 580572.484 93.472 
3 21 4 11.158440 105 46 38.154558 68.409 2330873.187 580572.485 93.471 
4 21 4 11.158554 105 46 38.154456 68.402 2330873.190 580572.482 93.464 
5 21 4 11.158434 105 46 38.154552 68.405 2330873.186 580572.485 93.467 
6 21 4 11.158530 105 46 38.154486 68.409 2330873.189 580572.483 93.471 
7 21 4 11.158554 105 46 38.154522 68.410 2330873.190 580572.484 93.472 
8 21 4 11.158440 105 46 38.154468 68.402 2330873.187 580572.482 93.464 
9 21 4 11.158422 105 46 38.154492 68.405 2330873.186 580572.483 93.467 
10 21 4 11.158464 105 46 38.154450 68.407 2330873.187 580572.482 93.469 
11 21 4 11.158482 105 46 38.154564 68.402 2330873.188 580572.485 93.464 
12 21 4 11.158428 105 46 38.154528 68.405 2330873.186 580572.484 93.467 
13 21 4 11.158566 105 46 38.154450 68.407 2330873.190 580572.482 93.469 
14 21 4 11.158566 105 46 38.154510 68.402 2330873.190 580572.484 93.464 
15 21 4 11.158494 105 46 38.154504 68.405 2330873.188 580572.483 93.467 
16 21 4 11.158518 105 46 38.154450 68.402 2330873.189 580572.482 93.464 
17 21 4 11.158536 105 46 38.154444 68.402 2330873.190 580572.482 93.464 
18 21 4 11.158554 105 46 38.154420 68.403 2330873.190 580572.481 93.465 
19 21 4 11.158452 105 46 38.154564 68.410 2330873.187 580572.485 93.472 
20 21 4 11.158464 105 46 38.154516 68.401 2330873.187 580572.484 93.463 
21 21 4 11.158446 105 46 38.154474 68.409 2330873.187 580572.483 93.471 
22 21 4 11.158524 105 46 38.154462 68.408 2330873.189 580572.482 93.470 
23 21 4 11.158470 105 46 38.154534 68.407 2330873.188 580572.484 93.469 
24 21 4 11.158542 105 46 38.154570 68.410 2330873.190 580572.485 93.472 
25 21 4 11.158548 105 46 38.154468 68.405 2330873.190 580572.482 93.467 
26 21 4 11.158494 105 46 38.154432 68.408 2330873.188 580572.481 93.470 
27 21 4 11.158578 105 46 38.154540 68.407 2330873.191 580572.485 93.469 
28 21 4 11.158512 105 46 38.154474 68.405 2330873.189 580572.483 93.467 
29 21 4 11.158500 105 46 38.154462 68.405 2330873.188 580572.482 93.467 
30 21 4 11.158464 105 46 38.154444 68.402 2330873.187 580572.482 93.464 
... ........................ ............................ ........... .................... .................. ............ 
Table 2. Results of processing of monitored data on step 4, 5 of An Binh high-rise building 
86 Khai Cong Pham/Journal of Mining and Earth Sciences 60 (3), 75 - 87 
Monitoring time X (m) Y (m) H (m) dX (mm) dY (mm) dP (mm) dh (mm) 2/8/2018 2330873.189 580572.484 93.471 2 3 3.6 -3 3/8/2018 2330873.191 580572.487 93.468 4 2 4.5 3 4/8/2018 2330873.195 580572.489 93.471 -2 -4 4.5 -5 5/8/2018 2330873.193 580572.485 93.466 -4 3 5.0 4 6/8/2018 2330873.189 580572.488 93.47 1 -4 4.1 -2 7/8/2018 2330873.19 580572.484 93.468 -5 -4 6.4 -6 8/8/2018 2330873.185 580572.48 93.462 2 4 4.5 -1 9/8/2018 2330873.187 580572.484 93.461 -1 -3 3.2 2 10/8/2018 2330873.186 580572.481 93.463 5 7 8.6 4 11/8/2018 2330873.191 580572.488 93.467 -2 -1 2.2 3 12/8/2018 2330873.189 580572.487 93.47 3 -3 4.2 1 13/8/2018 2330873.192 580572.484 93.471 2 2 2.8 -5 14/8/2018 2330873.194 580572.486 93.466 -4 -1 4.1 1 15/8/2018 2330873.19 580572.485 93.467 2 4 4.5 2 16/8/2018 2330873.192 580572.489 93.469 3 -4 5.0 -2 17/8/2018 2330873.195 580572.485 93.467 -4 -3 5.0 -1 18/8/2018 2330873.191 580572.482 93.466 -5 2 5.4 5 19/8/2018 2330873.186 580572.484 93.471 4 3 5.0 -2 20/8/2018 2330873.19 580572.487 93.469 2 1 2.2 4 21/8/2018 2330873.192 580572.488 93.473 -1 -4 4.1 -1 22/8/2018 2330873.191 580572.484 93.472 -2 1 2.2 -2 23/8/2018 2330873.189 580572.485 93.47 4 3 5.0 5 24/8/2018 2330873.193 580572.488 93.475 2 -3 3.6 -5 25/8/2018 2330873.195 580572.485 93.47 -6 -3 6.7 1 26/8/2018 2330873.189 580572.482 93.471 6 4 7.2 2 27/8/2018 2330873.195 580572.486 93.473 -3 -2 3.6 -2 29/8/2018 2330873.192 580572.484 93.471 -1 3 3.2 6 29/8/2018 2330873.191 580572.487 93.477 -2 -4 4.5 -5 30/8/2018 2330873.189 580572.483 93.472 4 2 4.5 -4 31/8/2018 2330873.193 580572.485 93.468 
Table 3. The displacements of An Binh building during 1 month 
 Khai Cong Pham/Journal of Mining and Earth Sciences 60 (3), 75 - 87 87 of monitoring stations has been studied, developed, and tested by specialized equipment. It works well, stably, continuously and ensuresthe required accuracy to monitor deformation and displacement of the construction works up to 3 mm in horizontal and 5 mm in height. 
Acknowledgements This research was financially supported by the Hanoi People's Committee (grant number 01C-4/08-2016-3) and the Hanoi Department of Science and Technology. 
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