High frequent total station measurements for the monitoring of bridge vibrations

Abstract

Robotic total stations (RTS) are frequently used for the measurement of temperature induced bridge deformations or during load testing of bridges. In experimental setups, total stations have also been used for the measurement of dynamic bridge deformations. However, with standard configurations the measurement rate is not constant and on average an update rate of 7–10Hz can be achieved. This is not sufficient for the vibration monitoring of bridges considering their natural frequencies which are also in the same range. In this paper, we present different approaches to overcome these problems. In the first two approaches we demonstrate how the measurement rate to prisms can be increased to 20Hz to determine vertical deformations of bridges. Critical aspects like the measurement resolution of the automated target tracking and the correct sequence of steering commands are discussed. In another approach we demonstrate how vertical bridge vibrations can be measured using an image assisted total station (IATS) and corresponding processing techniques. The advantage of image-based methods is that structural features of a bridge like bolts can be used as targets. Therefore, no expensive prisms have to be mounted and access to the bridge is not required. All approaches are verified by laboratory investigations and their suitability is proven in a field experiment on a 74m long footbridge. In this field experiment the natural frequencies derived from the total station measurements are compared to the results of accelerometer measurements.

Mems Based Bridge Monitoring Supported by Image-Assisted Total Station

“…Ehrhart and Lienhart (2015a) performed displacement and vibration monitoring of a footbridge structure by capturing video frames from the telescope camera of an IATS for a circular target marking rigidly attached to the structure. Ehrhart and Lienhart (2015b) and Lienhart et al (2017) were carried out vibration analysis of a footbridge structure using an IATS of type Leica MS50 with a sampling frequency of 10 Hz, an RTS of type Leica TS15 with a sampling frequency of 20 Hz and an accelerometer of type HBM B12/200 with a sampling frequency of 200 Hz based on measurements of the circular target markings and structural features such as bolts of the bridge structure. Omidalizarandi et al (2018) used an IATS of type Leica MS50 with sampling frequency of 10 Hz for displacement and vibration analysis of a footbridge structure.…”

TLS for Dynamic Measurement of the Elastic Line of Bridges

“…Thanks to the capability to transfer data even via the Internet and be managed remotely, they are used to monitor slopes and large structures [8,9]. The sampling frequency up to 7 Hz allows its use for dynamic measurements [10,11], but it is not possible to track more points at the same time; (3) GNSS satellite surveying is often used for tall buildings and large span bridges [12][13][14]. It is possible to obtain an accuracy of a few millimeters, while the acquisition frequency reaches 20 Hz.…”

Influence of Time Delays of Robotic Total Stations Witch High Sampling Frequency on Accuracy of Measurements to Moving Prisms

“…In practice, the record of vertical and horizontal angles does not occur at the same moment either, which is conditioned by the various instrumental adjustments introduced. During the performance of the measurement, the actions of the four types of sensors affect the measurement time: angle encoders, ATR -automatic target recognition system, total station main axis tilt compensator and EDM -electro-optical INFLUENCE OF TIME DELAYS OF ROBOTIC TOTAL STATIONS WITCH HIGH SAMPLING... [14]. The angular values calculated by the instrument take into account the quantities contained in formulas -Eq.…”