# Experimental Research of the Structure Condition Using Geodetic Methods and Crackmeter
###### Abstract  
The article presents an approach to monitoring the structure's condition with two measurement methods: the SHM-X crackmeter and the classic geodetic method of determining displacements, supplemented with additional information on the condition of the external environment obtained from thermal images. The study aimed to propose an approach combining geodetic and non-geodetic methods of assessing the condition of a structure and its effectiveness in practical application. The research facility is a public utility building of the Bydgoszcz University of Technology with a reinforced concrete structure. Objects of this type require periodic tests of their constancy. Interpreting the test results and identifying possible dangerous states that may indicate the risk of a construction failure is extremely important. The results presented in the article are an extension of the previous ones, in which several factors that could have a destructive effect on the structure were excluded. Observation of the object showed that only the reinforced construction plate is deformed. The only factor influencing the change in structure geometry is thermal changes. As part of the tests in places where cracks were noticed, the SHM-X crackmeter was used to measure the cracks' opening. In the geodetic research, measurements of the measurement and control network displacement were carried out, in which the TDRA6000 laser station measurement technology was used. The control points were also placed in places where the width of the cracks was directly observed. The proposed approach, with the applied calculation scheme and supplementing the information with the temperature measurement with thermal images, showed the submillimeter accuracy of the determined 3D displacements of the controlled points. Additionally, the parallel application of these methods gives a complete picture of changes in the structure elements, in which signs of destruction appear under the influence of stress. structural health monitoring; displacement surveying; breakdowns of building structures; civil engineering +
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and challenging task [4,5]. Therefore, the research process, which supports the assessment of the technical condition of the structure, is supplemented with measurements of displacements and deformations using geodetic and non-geodetic techniques. The primary symptom of negative phenomena occurring in building objects is their displacements and deformations. Geodetic monitoring is used, among other things, to determine displacements and deformations of engineering structures. It includes measurements, the subsequent analysis of which allows concluding the dynamics of the occurrence of changes in the structure. These measurements also provide information on the geometrical state of objects and changes in time and allow for obtaining additional information, for example, on the object's surface and volume [6, 7, 8]. The geodetic monitoring method depends on the object's structure, its location in space, the size and speed of changes, and the geodetic technology that can be used and conditioned by the measurements' cyclical nature [9, 10, 11]. The displacements are monitored by performing a measurements series of the measurement network and control points set up in the object, and the structure should be optimized in terms of the possibility of making measurements and the correctness of determining displacements [12, 13, 14]. Modern measuring technologies enable the implementation of tasks that have not been possible until now by traditional methods while ensuring the required precision. Currently, construction objects and subsoil can be monitored using classic geodetic methods [14, 15], the GNSS system and gravimetric measurements [16, 17, 18], unmanned aerial vehicles, and laser scanning [19, 20, 21], and supplemented with GIS technology [22, 23].