Krzysztof Holak

Monitoring of a civil structure’s state based on noncontact measurements

In this article, the comparison of two noncontact measurement methods dedicated to civil engineering structures’ state examination is presented. The vision-based method computes the displacement field of the analyzed structure by means of the digital image correlation coefficient. The system consists of one or more high-resolution digital cameras mounted on a head or on portable tripods. The developed methodology and created software application embedded in an MS-Windows operating system are presented. The second system measures the deflection of the structures by means of a radar interferometer. In both cases, it is possible to measure many points on the structure simultaneously. This article presents a comparison of the displacement field measurement performed on a field setup, as well as the span of a steel bridge designed for tram traffic. Both systems are described, with special attention given to their application in measurements of civil engineering structures. This article demonstrates a preliminary test performed to verify both of the noncontact systems in relation to high-accuracy measurement devices, the precise surveying level, and the electronic dial indicator of displacement. The experiment was designed intentionally to simulate the geometric conditions of the real structure, but the displacement values were generated and controlled by the operator. As a key study, a steel viaduct subjected to an operational load was measured, as a type of structure for which the observation is required in terms of structural health monitoring. It was subjected to the operational load caused by tram traffic. Both examined systems were applied. The accuracy analysis of both systems was investigated, and the obtained results were discussed.

Vision based condition assessment of structures

In this paper, a vision-based method for measuring a civil engineering constructions in-plane deflection curves is presented. The displacement field of the analyzed object which results from loads was computed by means of a digital image correlation coefficient. Image registration techniques were introduced to increase the flexibility of the method. The application of homography mapping enabled the deflection field to be computed from two images of the structure, acquired from two different points in space. An automatic shape filter and a corner detector were implemented to calculate the homography mapping between the two views. The developed methodology, created architecture and the capabilities of software tools, as well as experimental results obtained from tests made on a lab set-up and civil engineering constructions, are discussed.

A structure's deflection measurement and monitoring system supported by a vision system

Abstract In this paper a vision-based method for measuring vertical deflection of large engineering structures under load is presented in example of crane working arm deflection measurements. The deflection is computed by means of a digital image correlation technique embedded in the vision-based system. The results of measurements performed on the vision system were compared with data obtained using a Leica Laser Tracker system. The comparison revealed proper functioning of the developed vision system in industrial conditions.

Structure's Condition Monitoring Based on Optical Measurements

In the paper the vision-based method of civil engineering constructions in-plane deflection measurement and state monitoring is presented. The displacement field of the analyzed structure resulting from a load was computed by means of the digital image correlation coefficient. The application of homography mapping enabled the deflection curve to be computed from two images of the construction acquired from two distinct points in a space. There developed methodology, created software tool as well as experimental results obtained from tests made on lab set-ups and a civil engineering construction are investigated. The experiments are carried out on the lab setup consisting of SRL high resolution digital cameras and the steel frame loaded by a point force. The vision based method results are compared with other contact and non-contact measurement techniques. The deflection of the tram viaduct is investigated and results are compared with the data obtained by the interferometric radar.

Application of Vision Based Damage Detection for Real Civil Engineering Structure

Structural Health Monitoring (SHM) is an emerging field of technology that involves the integration of sensors, data transmission, processing and analysis for detection, as well as localization and assessment of damage which can lead to its failure in the future [1,. In general, SHM methods can be divided into two groups: local and global ones. The second group can be applied if a global change in the geometry of a structure can be observed. In practice, the most commonly used methods of damage detection are based on the analysis of variations in various dynamic properties caused by damage [3,. However, the excitation of large structures can be costly and difficult. The acquisition of static deflection requires much less effort, which makes the damage detection methods based on changes in deflection curves more attractive for practical use [5-1. Damage detection and localization methods require a densely sampled deflection curve.

Experimental assessment of rectification algorithm in vision-based deflection measurement system

Abstract An uncertainty assessment of a vision-based method for the measurement of a structure’s in-plane deflection is presented. In the investigated approach, the displacements of measurement points in the structure under load are computed by means of digital image correlation. The application of homography mapping enables the deflection field to be computed from two images of the structure acquired from distinct points in space. The impact of the camera’s pose and changes in focal length on the performance of the developed vision algorithm is investigated. The paper presents and discusses the influence of rectification algorithm on the quality of the vision-based measurement system as well.

Application of vision measurements for modal analysis of wires for the purpose of overhead transmission lines monitoring

Overhead transmission power lines are still one of the crucial elements of electro-energetic system. There are obvious advantages of using overhead transmission in the distribution of electricity. The amount of energy transported through a power line is determined by the distance between the wire and the ground or other objects placed beneath it (eg. trees). This distance is not fixed and depends on the overhang of the wire. This, in turn, is determined by many factors such as ambient temperature, humidity, precipitation, the value of current flowing through the wire. In order to optimize the wires electrical load, the monitoring of that overhang is required. One way to measure it is the non-contact measurement by vision system. It has the advantage, that using high-speed cameras respectively it also allows for vibration measurement and analysis of dynamic performance. That is very important while the wires are susceptible to the influence of wind, and the resulting vibrations interfere with the correct measurement of the overhang. The paper presents the results of vision measurements of the system vibrations and modal analysis carried out on their basis. The study was conducted on a specially made laboratory stand.

Oblique-viewing endoscope calibration in the diagnostics and treatment in the pelvis minor area

Abstract Urinary incontinence (UI) is a common condition, especially in women, and affects the quality of life in a physical, social, and economic meaning. Despite improvements in surgical techniques and the implementation of minimally invasive procedures, male and female stress UI still affects their well-being. Treatment limitations have encouraged researchers to investigate new approaches, including those of tissue engineering. The injection of autologous mesenchymal-derived stem cells (AMDC) might rebuild the urethra sphincter function and minimize leakage symptoms. The treatment is carried out with a rigid endoscope. The aim of this study is to present a practical calibration procedure for an oblique-viewing endoscope imaging system. This article presents the results of an examination of the variability of the internal camera’s parameters with the angle of rotation of the endoscope’s cylinder. The research proves that the most variable parameters are the coordinates of the image plane’s principal point. The developed model of variability can be implemented as a simple look-up table in a real-time operating device. In this article, a tool is proposed for the computation of the relative angle of cylinder’s rotation based only on images. All developed methods can be implemented in a robot-assisted system for an AMDC urethra sphincter injection procedure.