Παρακολούθηση ταλαντώσεων τεχνικών έργων με χρήση συγχρονισμένων ρομποτικών γεωδαιτικών σταθμών. Εφαρμογή στην υψηλή γέφυρα του Ευρίπου

Abstract

Η παρούσα διπλωματική εργασία έχει ως αντικείμενο μελέτης αφενός την αξιολόγηση της χρήσης των αυτόματα ελεγχόμενων γεωδαιτικών σταθμών (RTS) στην παρακολούθηση ταλαντώσεων μιας γέφυρας και αφετέρου τη σύγκριση διαφορετικών γεωδαιτικών σταθμών αυτού του είδους, έχοντας πρώτα συγχρονίσει τον χρόνο που καταγράφουν. Απώτερος σκοπός είναι να γίνει αξιολόγηση των δυνατοτήτων των γεωδαιτικών σταθμών σε τέτοιου είδους εφαρμογές, να γίνει σύγκριση των μετρήσεων τους σε κοινούς στόχους και τέλος να εξαχθούν συμπεράσματα για τη συμπεριφορά της γέφυρας . Στο πρώτο κεφάλαιο γίνεται μια αναφορά στο αντικείμενο της μελέτης ταλαντώσεων κατασκευών, αναφέρονται τα όργανα με τα οποία υλοποιούνται οι διάφορες μεθοδολογίες, επισημαίνονται χρήσιμες έννοιες κατανόησης όρων που χρησιμοποιούνται στην εργασία αυτή και παρουσιάζεται μια σειρά εφαρμογών ελέγχου ταλαντώσεων γεφυρών. Στο δεύτερο κεφάλαιο γίνεται περιγραφή των χαρακτηριστικών των αυτόματα ελεγχόμενων γεωδαιτικών σταθμών (RTS) αφού είναι και τα κύρια όργανα που χρησιμοποιήθηκαν για το σκοπό αυτής της διπλωματικής εργασίας, των σφαλμάτων αυτών και περιγράφονται τα χαρακτηριστικά των αντίστοιχων γεωδαιτικών σταθμών IS της εταιρείας Topcon και VX της εταιρείας Trimble τα οποία χρησιμοποιήθηκαν. Στο τρίτο κεφάλαιο παρέχονται λεπτομέρειες για το πεδίο εφαρμογής, που είναι η καλωδιωτή γέφυρα του Ευρίπου στη Χαλκίδα και για το δίκτυο παρακολούθησής της. Εν συνεχεία γίνεται αναφορά στην επιλογή των πειραμάτων, την προετοιμασία και την διεξαγωγή τους. Στο τέλος του κεφαλαίου περιγράφονται οι απαραίτητοι υπολογισμοί που έγιναν ώστε να γίνει η επεξεργασία των πρωτογενή δεδομένων με σκοπό την ανάλυσή τους και την εξαγωγή χρήσιμων συμπερασμάτων. Στο τέταρτο κεφάλαιο γίνεται ανάλυση όλων των παραγόμενων διαγραμμάτων των χρονοσειρών στα πεδία του χρόνου, χώρου και συχνοτήτων. Στο πέμπτο κεφάλαιο γίνεται καταγραφή όλων των συμπερασμάτων που εξήχθησαν από όλες τις διαδικασίες της εργασίας αυτής και γίνονται προτάσεις για περαιτέρω διερεύνηση.

Aim of this thesis is firstly to evaluate the use of automatically controlled total stations (RTS) to monitor oscillations of a bridge and also the comparison between two different stations of this type having synchronized the time of record with the global time zone UTC. As an ultimate goal is set to evaluate the abilities of the geodetic stations in those applications, afterwards to compare the measurements in common objectives and finally to draw conclusions about the response of the bridge. In the first chapter, there is a reference to the research of oscillations of the structures and the equipment/instruments used in the various methodologies implemented. Furthermore, there is citation of useful meanings of the terms used in this thesis and presentation of a series of applications in the dynamic deformation of structures. In the second chapter, there is description of the characteristics of automatically controlled total stations (RTS)-since they are the main instruments used for this thesis- and the errors performed. In addition, the technical characteristics used of controlled total station of the IS of Topcon company and the VX of Trimble company are stated. In the third section, there are the details on the scope of the cable bridge Evripos in Chalkida and its network monitoring are provided. Furthermore, the chapter refers to the selection of experiments, the preparation and their conducting. Finally, the necessary calculations are mentioned in detail in order to process the raw data to analyze them and draw useful conclusions. In the fourth chapter, there is the analysis of all generated graphs of time series in the area of time-space-frequencies. In the fifth chapter, there is the recording of all conclusions reached by the majority of processes of this thesis and a number of suggestions are provided for further investigation.

By processing and analyzing the measurements, various conclusions were accrued, which were afterwards divided in three categories: The first category refers to those that relate to the accuracy and reliability of two geodetic stations used in the experiments. The second category refers to the evaluation of the methodology used with regards to the use of the two robotic stations, whose chronometers were synchronized so as to compare the results, and The third category mentions the conclusions reached for the research conducted referring to the cable-stayed bridge of Chalkida in terms of response and correspondence to data of study or previous investigations.

As far as the reliability of RTS used, the following conclusions were revealed: The time series of the two robotic stations presented recording gaps mostly in range of 1 measurement per minute and a number of times for a longer time period. Both stations for some intervals were unable to record entire cycles of oscillations, also reflected in graphs where there were periods with no changes recorded. This fact is probably present due to the reason that the distance requires a longer time period for the recording of the station opposed to the angles immediately recorded by taking the measurement. The uncertainty of the coordinates calculated in the order of centimetres (±5mm). The two stations locked –at a different point– the target recorded in a number of times by both the simple and the OMNI angle.

In the thesis, two robotic stations were used after having their clocks synchronized and having simultaneous measurements in common or not targets taken. The following conclusions were reached by using this method: The synchronization of the stations was successful and it might provide us with information on different targets at the same time. The data can be combined with other measurements of geodetic equipment such as GPS or geotechnical instruments. By using two different stations, it was found that regarding movements close or within the limits of the calibration of the instruments, the equipment used did not record any similar changes. Ιn the cases where gaps were present during the recordings in a geodetic station –in time periods were no significant changes exist– the lost information of the data of the second station was found as long as the same target was aimed. As far as the vibration amplitudes are concerned, there was accordance of the two stations in cases where intense and long vibrations were present and partial inconsistency in low-range movements. This specific method provided the ability of taking measurements checkpoints placed in different positions over the bridge in order through the processing of the measurements to determine the response of the bridge on more than one element in a given time period The exact time of recording was not clearly estimated, since the two stations recorded per second broken in integer seconds, and as a result there is an error of ±0.5sec The frequency of recording of the measurements was marginally adequate, as according to Nyquist theorem, the sample taking by examining the flexible structure with natural frequency less than 1Hz should be in the range of at least 2Hz. For this reason, the main frequencies generated marginal and the existence of loud noise of the estimate frequencies.

One of the main objectives of this thesis was the conduct of conclusions for the dynamic response of the cable bridge of Evripos. The results are mentioned below:

For the longitudinal axis of the bridge, no significant oscillations were recorded neither on the pillars or the deck and the majority of the values were within the limits of the uncertainty of the two stations. In the transverse axis of the bridge and in specific measurements of the targets placed on pillars recorded, significant oscillations range of 3cm were recorded. On the vertical axis, and specifically the middle of the opening of the deck, notable oscillations of 6cm were recorded. Τhe main oscillation frequency calculated using the spectral analysis using the Lomb normalized periodogramm was equal to 0.43Hz from both geodetic stations with small deviations ranged in millimeters of Hz (0.001Hz). The measurements performed on targets in anti-diametrical points of the two pillars M5 and M6 recorded the counter-oscillation during the pass of the operating load (passing vehicles).