Measurement of deflections and of oscillation frequencies of engineering structures using Robotic Theodolites (RTS)

Abstract The Robotic Theodolite or Robotic Total Station (RTS) is a new generation geodetic instrument that can automatically record the changing coordinates of a moving target (reflector). RTS was so far used for monitoring of static and very slow displacements. This limitation was imposed by some characteristics of these instruments (real sampling rate In particular, it was shown that: (1) the maximum real sampling rate of RTS is 6–7 Hz, but since sampling rate is variable, aliasing-free results can be obtained above the Nyquist frequency. (2) The potential to record oscillations depends on the maximum angular velocity of the instrument and on the maximum velocity of the moving target; for velocities up to about 10 cm/s in field studies, results are very precise. On the contrary, for targets moving with maximum velocities > 15 cm/s, some displacements cycles are not well-defined or are lost, and hence, the accuracy of the oscillation amplitude and frequency are lower. (3) RTS can be used to measure small (on the order of a few mm) amplitudes of oscillation, and to some degree of frequencies of oscillation of various relatively stiff engineering structures (modal frequencies > 1 Hz, up to 3–4 Hz). This potential is demonstrated on the basis of several field examples, including the monitoring of two bridges with dominant modal frequencies > 1.5 Hz. Obviously, these limits reflect the most unfavorable cases of application of RTS, and higher period/larger amplitude oscillations or other deflections can be successfully measured if the main requirement for this type of instrument is satisfied: an unobstructed view of a reflector at a maximum distance of a few hundred meters from an RTS set on stable ground.

[1]  Tracy Kijewski-Correa,et al.  Experimental verification of a GPS network: characterization and removal of multipath effects , 2006, SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[2]  Christopher Watson,et al.  Structural Monitoring of Cable-Stayed Bridge: Analysis of GPS versus Modeled Deflections , 2007 .

[3]  Stathis C. Stiros,et al.  Monitoring dynamic and quasi-static deformations of large flexible engineering structures with GPS: Accuracy, limitations and promises , 2006 .

[4]  Edward M. Mikhail,et al.  Observations And Least Squares , 1983 .

[5]  Hisao Kikuta,et al.  Bridge deflection measurement using digital image correlation , 2007 .

[6]  Chris Rizos,et al.  Detection of Wind-Induced Response by Wavelet Transformed GPS Solutions , 2003 .

[7]  Stathis C. Stiros,et al.  Accurate measurements with primitive instruments: the “paradox” in the qanat design , 2006 .

[8]  Wujiao Dai,et al.  Assessment of Dynamic Measurement Accuracy of GPS in Three Directions , 2006 .

[9]  Tommy H.T. Chan,et al.  Dynamic interaction of long suspension bridges with running trains , 2000 .

[10]  V. Gikas,et al.  Full Scale Validation of Tracking Total Stations Using a Long Stroke Electrodynamic Shaker , 2006 .

[11]  J. M. Rüeger.  Electronic Distance Measurement , 1990 .

[12]  John G. Proakis,et al.  Digital signal processing (3rd ed.): principles, algorithms, and applications , 1996 .

[13]  William F. Teskey,et al.  DYNAMIC MONITORING OF DEFORMING STRUCTURES : GPS VERSUS ROBOTIC TACHEOMETRY SYSTEMS , 2001 .

[14]  Stathis C. Stiros,et al.  Ladon dam (Greece) deformation and reservoir level fluctuations: evidence for a causative relationship from the spectral analysis of a geodetic monitoring record , 2005 .

[15]  John G. Proakis,et al.  Digital Signal Processing: Principles, Algorithms, and Applications , 1992 .

[16]  Stathis C. Stiros,et al.  Induced deformation during tunnel excavation: Evidence from geodetic monitoring , 2005 .

[17]  James M. W. Brownjohn.  Lateral loading and response for a tall building in the non-seismic doldrums , 2005 .

[18]  Alan Dodson,et al.  Integrating a Global Positioning System and Accelerometers to Monitor the Deflection of Bridges , 2004 .

[19]  H. Netzel,et al.  Amsterdam's North/South metroline , 1999 .

[20]  Maria Tsakiri,et al.  Evaluation of dynamic response and local soil effects of the Evripos cable-stayed bridge using multi-sensor monitoring systems , 2005 .

[21]  S. Pagiatakis,et al.  Stochastic significance of peaks in the least-squares spectrum , 1999 .

[22]  Stathis C. Stiros,et al.  Spectral analysis of unevenly spaced or discontinuous data using the normperiod code , 2008 .

[23]  William H. Press,et al.  Numerical recipes in C , 2002 .

[24]  Alan Dodson,et al.  Detecting bridge dynamics with GPS and triaxial accelerometers , 2007 .

[25]  Michael A. Duffy,et al.  AN AUTOMATED AND INTEGRATED MONITORING PROGRAM FOR DIAMOND VALLEY LAKE IN CALIFORNIA , 2001 .

[26]  Jagmohan Humar,et al.  Dynamic of structures , 1989 .