On-line GPS Integrity Monitoring and Deformation Analysis For . . .

Recent reports by investigators describe how high precision GPS sensors deployed on large engineering structures (such as dams, bridges, towers and tall buildings) can provide continuous real-time measurements, which can, in turn, be used to indicate displacements and vibrations caused by temperature changes, wind loading, distant earthquakes, landslides, etc. This information can be made available to the system manager, or interested parties, on a continuous basis, or whenever a preset displacement threshold is exceeded. The response of the structure can then be assessed according to the displacement thresholds reached or the changed dynamic characteristics. In the case of an alarm, the system manager can make a decision to, for example, close the structure for further inspection. This creates an opportunity for real-time structural health monitoring, and therefore leads to enhanced public safety. I

A Software Implementation of Multi-Sensor Data Analysis

Some recent developments in structural monitoring schemes have discussed the complementary benefits of integrating GPS positioning with other sensors. This leads to the challenge of having to deal with potentially vast amounts of data, requiring heavy computational and communication loads. Efficient data reduction techniques therefore become necessary tools for handling the large amounts of data generated. These techniques can be easily implemented in projects where the processing software runs on a centrally located control station PC, receiving real-time streams of data, and computing precise positions for all stations located on the target structure. In such schemes, integrity assessment also becomes an important task if the objective is to determine the actual response signature of the structure. This problem can be addressed by using statistical tools in which one or several parameters may change abruptly. In the first instance, biases or outliers due to sensor malfunction should be detected as soon as possible, and then the sensor isolated (and ultimately repaired) in order to guard against incorrect (or biased) deformation signals

An Approach to GPS Analysis incorporating Wavelet Decomposition

The classical least-squares processing of GPS measurements generates residuals, which contains the signature of both unmodelled systematic biases and random measurement noise. It is desirable to extract (or minimise) the systematic biases contained within the GPS measurements. This would be relatively straightforward if there were some apriori knowledge of the phenomena related to these errors. Common ways of dealing with this problem include (i) changes to the stochastic modelling, and (ii) redefinition of the functional model

A framework in support of structural monitoring by real time kinematic GPS and multisensor data

Due to structural damages from earthquakes and strong winds, engineers and scientists have focused on performance based design methods and sensors directly measuring relative displacements. Among the monitoring methods being considered include those using Global Positioning System (GPS) technology. However, as the technical feasibility of using GPS for recording relative displacements has been (and is still being) proven, the challenge for users is to determine how to make use of the relative displacements being recorded. This thesis proposes a mathematical framework that supports the use of RTK-GPS and multisensor data for structural monitoring. Its main contributions are as follows:(a) Most of the emerging GPS-based structural monitoring systems consist of GPS receiver arrays (dozens or hundreds deployed on a structure), and the issue of integrity of the GPS data generated must be addressed for such systems. Based on this recognition, a methodology for integrity monitoring using a data redundancy approach has been proposed and tested for a multi-antenna measurement environment. The benefit of this approach is that it verifies the reliability of both the measuring instruments and the processed data contrary to the existing methods that only verifies the reliability of the processed data.(b) For real-time structural monitoring applications, high frequency data ought to be generated. A methodology that can extract, in real-time, deformation parameters from high frequency RTK measurements is proposed. The methodology is tested and shown to be effective for determining the amplitude and frequency of structural dynamics. Thus, it is suitable for the dynamic monitoring of towers, tall buildings and long span suspension bridges.(c) In the overall effort of deformation analysis, large quantities of observations are required, both of causative phenomena (e.g., wind velocity, temperature, pressure), and of response effects (e.g., accelerations, coordinate displacements, tilt, strain, etc.). One of the problems to be circumvented is that of dealing with excess data generated both due to process automation and the large number of instruments employed. This research proposes a methodology based on multivariate statistical process control whose benefit is that excess data generated on-line is reduced, while maintaining a timely response analysis of the GPS data (since they can give direct coordinate results).Based on the above contributions, a demonstrator software system was designed and implemented for the Windows operating system. Tests of the system with datasets from UNSW experiments, the Calgary Tower monitoring experiment in Canada, the Xiamen Bank Building monitoring experiment in China, and the Republic Plaza Building monitoring experiment in Singapore, have shown good results

Toward The Implementation Of On-Line Structural

The aim of this paper is twofold. First, it describes a pilot project in Singapore, in which an RTKGPS system has been installed for the purpose of monitoring the behaviour of a high rise building. This system will contribute to a project of monitoring that commenced in 1995 with the installation of two pairs of accelerometers and two UVW anemometers. The aim of this project is to capture the building loading and dynamic response during strong winds and remote earthquakes to aid local design code development. The GPS monitoring system installed on the Republic Plaza building (at 280m, the maximum height of any Singaporean building) generates on-line antenna coordinate measurements. These will complement and corroborate the acceleration data to provide the complete picture of the building displacement across the full spectrum of loading frequencies, allowing for direct estimation of lateral loads. The system design and installation is described. The second objective of this paper is to describe a wavelet analysis procedure that has been proposed for the extraction of both the high and low frequencies of the structural dynamics from the 'raw' RTK-GPS results. The results of tests of this time series analysis procedure will be presented