Home Articles Monitoring high-rise building deformation using Global Positioning System

Monitoring high-rise building deformation using Global Positioning System

Wan Aziz, W. A. Othman Z. & Najib H
Department of Geomatic Faculty of Engineering & Geoinformation Science
University Technology Malaysia,Skudai Malaysia
Tel: 07-5502875, Fax: 07-5566163
[email protected]

Deformation of engineering structures is often measured in order to ensure that the structure is exhibiting a safe deformation behaviour. For example, the deformation of high-rise building can be monitored by using geodetic method such as Global Positioning System (GPS). This paper discusses the monitoring of high-rise building using the GPS methods. The case study is the KOMTAR building, in Penang, Malaysia. Six control points have been established whereby four of them is located on top of the building itself, and the other two is located at the KOMTAR Plaza compounds.. The field measurements have been carried out in two different epochs, October 2000 and February 2001. The GPS observation and deformation data have been processed and analysed by using the SKI TM and GPSAD2000 softwares, respectively. The results showed that there is no movement occurred in the building.

Engineering structures (such as dams, bridges, high rise buildings, etc.) are subject to deformation due to factors such as changes of ground water level, tidal phenomena, tectonic phenomena, etc. Cost is more than offset by savings and by improvements in safety both during and after constructions. As a result, the design, execution and analysis of such surveys are a matter of considerable practical importance. Expanded resource development, the trend towards potentially-deformation-sensitivity engineering and construction projects, and growing geosciencetific interest in the study of crustal movement have all combined to increase awareness of the need for a comprehensive integrated approach to the design and analysis of such deformation surveys. Deformation refers to the changes of a deformable body (natural or man-made objects) undergoes in its shapes, dimension and position. Therefore it is important to measure this movements for the purpose of safety assessment and as well as preventing any disaster in the future.

Deformation measurement techniques generally can be divided into geotechnical, structural and geodetic methods (Teskey and Poster, 1988). The geodetic methods (highly understood by land surveyors) that can be used are Global Positioning System (GPS), close range photogrammetry, total station (terrestrial survey), very long baseline interferometry and satellite laser ranging. The survey methods can be further subdivided into the survey network method and direct measurement methods. In geodetic method there are two types of geodetic networks, namely the reference (absolute) and relative network (Chrzanowski et. al., 1986).

The selection of most appropriate technique or combination of techniques for any particular application will depend upon cost, the accuracy required, and the scale of the survey involves. Therefore several aspects related to the optimal design of the networks, measurement and analysis techniques suited to the monitoring surveys have to be considered. The design of monitoring scheme should satisfy not only the best geometrical strength of the network but should primarily fulfill the needs of subsequent physical interpretation of the monitoring results. Selection of monitoring techniques depends heavily on the type, the magnitude and the rate of the deformation. Therefore, the proposed measuring scheme should be based on the best possible combination of all available measuring instrumentation. A common feature for both geodetic and satellite methods in monitoring scheme involves the following three stages:

  • The development of a network configuration,
  • The execution process that runs a designed network into reality which deals with both the documentation of the proposed network stations and the actual field measurement techniques, and
  • The network analysis that deals with the processing and analysis of the collected geodetic data.

GPS Background and Structural High Rise Building
GPS is satellite based positioning system, which has been developed by the US Department of Defense (DoD) for real time navigation since the end of the 70’s. It has made a strong impact on the geodetic world. The main goal of the GPS is to provide worldwide, all weather, continuous radio navigation support to users to determine position, velocity and time throughout the world. It consists of three segments: the space, control and user segment. The GPS can be used for absolute and relative geodetic point positioning. Its primary task is to measure distances between 24 satellites in known orbits about 20,000 km above the earth and provide the user with the information of determining user’s position, expressed in the geocentric 3D coordinate system (WGS84).

GPS techniques have several advantages as a monitoring tool. The surprisingly high accuracies of relative GPS measurements are finding an application in monitoring surveys in areas where stations require intervisibility and weather conditions. Currently, with the deployment of the full satellite constellation, continuous and automated monitoring using GPS will become increasingly practical and cost-effective. Thus, the potentials of GPS as a super positioning tools brought a fresh air to the field of monitoring surveys, especially in areas where quick results could save lives and property. In principle, the monitoring of high-rise building using GPS can be performed episodically (epoch intervals) or continuously. Current GPS accuracy estimates range from 1-2 ppm for regional baseline vectors determined using commercial production software (DeLoach, 1989).

High-rise building is defines as a multistory building tall enough to require the use of a system of mechanical vertical transportation such as elevators. Although originally designed for commercial purposes, many high-rise buildings are now planned for multiple uses. They arose in urban areas where increased land prices and great population densities created a demand for buildings that rose vertically rather than spread horizontally, thus occupying less precious land area. The foundation of high-rise buildings must support very heavy gravity loads and they usually consist of concrete piers, piles or caissons that are sunk into the ground. The most important factor in the design of high-rise buildings is the building’s need to withstand the lateral forces imposed by winds and potential and ground movements. Most high-rise buildings have frames made of high strength steel and concrete. Their frames are constructed of columns (vertical-support members) and beams (horizontal-support members). Cross bracing or shear walls may be used to provide structural frame with greater lateral rigidity in order to withstand wind stress. Even more stable frames use closely spaced columns at the building’s perimeter, or they use the bundled-tube system, in which a number of framing tubes are bundled together to form exceptionally rigid columns. Curtain walls enclose high-rise buildings; these are non-load-bearing sheets of glass, masonry, stone or metal that is affixed to the building’s frame through a series of vertical and horizontal members called mullions and muntins.

Fig.1: KOMTAR building Penang
Case Study
The KOMTAR building in Penang has been chosen for the purpose of the deformation monitoring study. Figure 1 shows the view of the building, which is the tallest building in Penang. It is located in the little colonial and touristic George Town at 245 meter high (65 floors).

The observation network consists of 2 base stations, and 6 monitoring stations. Two observation campaigns are made for this study: The first campaign was carried out in November 2000 and the other in February 2001. All stations were surveyed by using 3 units of Leica 300 dual-frequency receivers. Static GPS surveying mode with relative positioning was used for all stations. Two GPS base stations, TLDM (P314) and Kg. Penaga (P288), were used for each GPS survey. In this study, geodetic control survey has been carried out to identify the stability of the monitoring stations KT1, KT2, KT3, KT4, KT5 and KT6 from the GPS observation. In order to achieve the maximum possible accuracy in deformation surveys, we try to keep all possible systematic errors constant by using only the same type of receiver in all survey campaign, use the same software, try to use similar geometry of satellites in the repeated measurements of individual baselines, and finally try to conduct all survey campaign in similar environmental conditions.

Result and Analysis
The GPS network adjustment of data from both epochs is accomplished using the Ski TM software with constrains network adjustment. The coordinates and standard deviations are shown in Table 1 and 2 for the 1 st epoch and 2 nd epoch, respectively. The comparison of standard deviations from these two GPS campaigns is plotted in Figure 2. As indicated in Figure 2, the standard deviations for the 1 st epoch are varied from 0 mm to 5 mm in horizontal components and from 0 to -3mm in vertical component, while in the 2 nd epoch, the corresponding values are varied from 0 mm to 9 mm in horizontal component and 0 mm to 6 mm in vertical component. Practically, the overall analyses have shown that the qualities of the observation data for these GPS campaigns are good.

The result for the residuals, standardised residuals, and internal/ external reliability is summarized in Table 3 – 6, respectively. Figure 3 and 4 depicts the accepted residual values and standardized residuals for epoch 1 and 2, respectively. It can be seen that the residual values in Table 3 and 5 are smaller than the standard deviation of the observations (see Table 1 and 2). Figure 5 and 6 shows the internal and external reliability for both epochs. The internal reliability for the first epoch is varies from 0.05 to 0.26 in horizontal and 0.04 to 0.07 in vertical component. While the second epoch varies from 0.06 to 0.24 in horizontal component and 0.06 to 0.012 in vertical component. The external reliability also small whereby it values is varies from 0.0001 to 0.0107 in horizontal and 0.0001 to 0.0072 in vertical component. The overall results have shown that the network has a good reliability.

The comparison of different adjusted coordinates has also been carried out for this experiment, and it is summarized in Table 7. Figure 7 illustrates this results. Here, it can be seen that the smallest and the biggest values is occured at station KT1 and KT5, respectively. The station KT5 has the values of -8.8 mm and 57.7 mm for the horizontal component and -10.6 mm for the vertical component. The station KT1 has the value of 1.3 mm and 16.7 mm for the horizontal components and -2.5 mm for the vertical component.
Table 1: Coordinate and standard deviation for 1st epoch

Station Coordinate X (m) Standard deviation of X (m) Coordinate Y (m) Standard deviation of Y (m) Coordinate Z (m) Standard deviation of Z(m)
P 314 6246578.6211 0.00000 -1140193.1164 0.00000 598604.6758 0.00000
P 288 6244748.2409 0.00000 -1143708.2813 0.00000 610775.9046 0.00000
KT1 6247164.3027 0.03417 -1138664.3150 0.02230 597852.2263 0.02230
KT2 6247161.5147 0.03399 -1138670.0366 0.02737 597869.9871 0.02744
KT3 6247164.1546 0.03530 -1138652.4298 0.02985 597876.0809 0.02771
KT4 6247166.9093 0.03683 -1138646.6376 0.02509 597858.3177 0.02202
KT5 6246953.3319 0.05364 -1138640.5030 0.03221 597803.4737 0.03242
KT6 6246962.3547 0.03080 -1138554.1557 0.02873 597868.8060 0.02902

Table. 2 : Coordinate and standard deviation for 2nd epoch

Station Coordinate X (m) Standard deviation of X (m) Coordinate Y (m) Standard deviation of Y (m) Coordinate Z (m) Standard deviation of Z(m)
P 314 6246578.6211 0.00000 -1140193.1164 0.00000 598604.6758 0.00000
P 288 6244748.2409 0.00000 -1143708.2813 0.00000 610775.9046 0.00000
KT1 6247164.3194 0.03045 -1138664.3137 0.03045 597852.2238 0.03045
KT2 6247161.5430 0.04146 -1138670.0388 0.03045 597869.9839 0.03045
KT3 6247164.1866 0.03724 -1138652.4483 0.02931 597876.0695 0.02981
KT4 6247166.9230 0.03487 -1138646.6411 0.03355 597858.2783 0.02961
KT5 6246953.3896 0.09400 -1138640.5132 0.05455 597803.4631 0.06201
KT6 6246962.3084 0.05774 -1138554.1645 0.04301 597868.7771 0.03864

Fig.2: Standard deviation for both epochs
A statistical test known as the congruency test is required to determine whether significant movements is occurred between the monitoring campaigns, i.e. to evaluate the stability of the control points. The application of congruency tests is quite simple. Initially, the congruency of common datum points at each epoch is evaluated by the global congruency test. If the test indicates that there is a significant movements, then the localization process is performed, follows by a similar test on the remaining datum points through the partial congruency test. In this study, the GPSAD200 software has been used to analyse the stability of all control points located at the KOMTAR building. Table 8 shows the baseline vector with two fixed points for epoch 1 and epoch 2. The deformation analysis is carried out for all observations. Results for the variance ratio and congruency test is summarised in Table 9. It can be seen form this table that the variance ratio test at significance level of 0.05 is passed for all observations, whereby the value is smaller than the critical value, i.e. (1.204 < 2.405). This shows that the variance factor is same for both GPS campaigns. The global congruency test at significance level 0.05 for the results is also implemented. The output of this global test indicates that all control points are in stable conditions – see Table 10.

The monitoring network is properly adjusted and analysed before the results are used in the deformation analysis. The SKI TM software has been used to process all GPS observation data. While, the analysis of deformation survey for the GPS observation has been carried out by using the GPSAD2000 software. The preliminarily presented results of the test surveys demonstrate that GPS survey has the potential to be used in monitoring of high-rise building. More research is required , however, to fully understand all sources of errors and their influence on GPS results for high precision deformation surveys because some anomalies in the GPS results still occur in geodetic measurements which cannot yet be fully explained.

Table 3: Residuals, Standard residuals and minimal detectable bias for 1st epoch

From To Residuals Standard Residuals Minimal Detectable Bias
X (mm) Y (mm) Z (mm) X Y Z X Y Z
P 314 KT1 1.01 0.46 -1.08 0.63 0.45 1.06 0.08 0.06 0.06
  KT2 0.85 0.34 -1.42 0.71 0.30 1.24 0.11 0.07 0.07
  KT3 0.33 -0.39 -1.97 0.36 0.40 1.33 0.14 0.10 0.06
  KT4 0.73 0.67 0.13 0.41 0.35 0.06 0.09 0.05 0.04
  KT5 -1.96 1.39 -2.67 1.16 0.79 1.56 0.26 0.07 0.07
  KT6 2.79 1.01 -0.61 2.64 0.66 0.42 0.09 0.06 0.08
P 288 KT1 -4.71 -2.28 5.28 0.65 0.47 1.08 0.08 0.05 0.05
  KT2 -9.21 -2.65 7.37 0.89 0.40 1.11 0.11 0.07 0.07
  KT3 -5.64 -2.60 6.70 0.36 0.24 1.21 0.15 0.11 0.07
  KT4 1.15 -0.02 0.77 0.78 0.56 0.06 0.21 0.12 0.06
  KT5 -5.93 -3.97 8.42 0.24 0.64 1.36 0.24 0.07 0.07
  KT6 -23.09 2.45 0.05 2.53 0.40 0.01 0.10 0.07 0.07

Table 4: External reliability for 1st epoch

Point X Y Z
KT1 0.0001 0.0001 0.0001
KT2 0.0017 0.0010 0.0005
KT3 0.0022 0.0022 0.0017
KT4 0.0016 0.0022 0.0018
KT5 0.0056 0.0019 0.0011
KT6 0.0007 0.0023 0.0023

Table 5: Residuals, Standard residuals and minimal detectable bias for 2nd epoch

From To Residuals Standard Residuals Minimal Detectable Bias
X (mm) Y (mm) Z (mm) X Y Z X Y Z
P 314 KT1 2.32 0.35 -0.88 1.48 0.22 0.56 0.07 0.07 0.07
  KT2 2.26 -0.16 -1.34 1.19 0.11 0.94 0.10 0.07 0.07
  KT3 2.30 -1.62 -2.87 1.80 0.99 1.87 0.11 0.06 0.07
  KT4 1.39 0.46 -3.71 1.35 0.33 1.76 0.11 0.09 0.06
  KT5 3.57 0.23 -3.66 0.73 0.07 0.81 0.18 0.11 0.12
  KT6 -1.10 -0.02 -3.48 0.54 0.01 1.08 0.18 0.09 0.07
P 288 KT1 -8.79 -1.36 3.37 1.49 0.23 0.57 0.07 0.07 0.07
  KT2 -11.43 0.55 6.44 1.26 0.08 0.99 0.10 0.07 0.07
  KT3 -12.74 -0.58 4.79 0.79 0.05 0.34 0.16 0.12 0.15
  KT4 -3.28 -3.18 6.95 0.14 0.19 0.89 0.24 0.18 0.10
  KT5 -1.79 -2.54 7.37 0.09 0.24 0.01 0.24 0.13 0.12
  KT6 0.13 -1.29 5.07 0.15 0.01 0.79 0.22 0.10 0.09

Table 6: External reliability for 2nd epoch

Point X Y Z
KT1 0.0000 0.0000 0.0000
KT2 0.0003 0.0002 0.0002
KT3 0.0065 0.0053 0.0059
KT4 0.0032 0.0048 0.0072
KT5 0.0107 0.0041 0.0027
KT6 0.0044 0.0042 0.0059

Table 7: Different of adjusted coordinate for both epoch
(Epoch 2-Epoch 1)

Station DX (mm) DY (mm) DZ (mm)
KT1 16.7 1.3 -2.5
KT2 -28.3 -2.2 -3.2
KT3 32.0 -1.85 -11.4
KT4 13.7 -3.5 -39.4
KT5 57.7 -10.2 -10.6
KT6 -46.3 -8.8 -28.9

Figure 3: Residuals for both epochs

Figure 4: The standardised residuals for both epochs

Figure 5: The internal reliability for both epochs

Table 8: Baselines vector of both epochs

From To   Epoch 1     Epoch 2  
P 314 KT1 DX (m) D Y(m) DZ (m) DX (m) D Y (m) DZ (m)
585.672 1528.797 -752.439 585.675 1528.799 -752.443
  KT2 582.885 1523.076 -734.675 582.899 1523.079 -734.679
  KT3 585.530 1540.691 -728.575 585.543 1540.684 -728.578
  KT4 588.277 1546.479 -746.366 588.288 1546.471 -745.360
  KT5 374.730 1552.600 -801.175 374.733 1552.601 -801.176
  KT6 383.706 1638.951 -735.864 383.698 1638.952 -735.864
P288 KT1 2416.109 5043.989 -12923.731 2416.166 5043.981 -12923.715
  KT2 2413.366 5038.271 -12905.991 2413.416 5038.237 -12905.985
  KT3 2415.970 5055.878 -12899.891 2416.073 5055.839 -12899.883
  KT4 2418.837 5061.712 -12917.591 2418.715 5061.672 -12917.696
  KT5 2205.150 5067.818 -12972.515 2205.167 5067.794 -12972.515
  KT6 2214.345 5154.101 -12907.099 2214.066 5154.130 -12907.178

Table 9: The variance ratio and the congruency test result

Statistical test Day1 Day2 Day3
Variance ratio test Passed Passed Passed
Global congruency test Passed Passed Passed