## 1 Introduction  
Controlling the stress-strain state of structures is important when high-rise buildings are put into operation. It is the uneven settlement of the foundation that leads to the cracking of the base of the building and its walls, and this can cause significant consequences. Simulation methods based on full design gravity load indeed demonstrate the distribution of deformation; however, they are used for predicting and preliminarily assessing the impact of loads on the building but cannot transmit the actual condition. [PERSON] et al. [1] using the geotechnical analysis of raft and piles (GARP) program for modelling the loading-determined Deformation Contours of Basements (Raft Foundation) on a 75-storey tower in Abu-Dhabi Plaza complex in Astana city (Kazakhstan). According to the analysis of basement raft deformations, the maximum settlement of the core of the building reached 39.6 mm, while for columns around the perimeter, it was only 13.4 mm (Figure 1). The settlement at each construction stage was calculated using the ratio of the vertical reaction at each stage to the vertical reaction at full design load using finite element analysis. The interaction between soils and piles and the stiffness parameters were established by using the GARP software. [PERSON] et al. [2] presented the results of the modelling of the same Abu-Dhabi Plaza high-rise building block with FLAC 3D program. According to the results, the estimated settlement for the core was 37.4 mm, while for columns it was 14 mm (Figure 2). Both simulation methods showed a similar pattern of radial load and settlement distribution, with the greatest influence at the center of the building. In order to determine the actual data on the strain-stress state of the basement raft area of the aforementioned high-rise building, the results of monitoring using fiber optics during the initial stage of building operation were considered. The results of the preliminary simulation helped  
Figure 1: Vertical deformation plan of raft foundation according to the simulation of [PERSON] et al. [1] using GARP software. Figure 2: Deformation contour plan of raft foundation according to [PERSON] et al. [2] simulation results with FLAC 3D program. to determine the placement of the fiber optic cable on the floor plan. The purpose of monitoring with the use of fiber optics was to observe the durability of concrete over time since the depth of the pit was significantly lower than the groundwater level, and the formation of cracks in concrete would allow water to penetrate them. Fiber optics (FO) became an alternative instrumental method for monitoring deformation and tracking maximum allowable stresses in building structures [3]. Even though fiber optics have been used for diverse purposes in many industries for a long time, the use of fiber optic cables as a strain sensing tool began relatively recently [4]. Over the course of several decades, a breakthrough was made not only in improving the quality of the fiber and reducing the losses in the transmission of a light pulse, but also in significantly reducing its market value. An advantage of using optical fibers (OF) as a measuring body is energy passivity and intrinsic safety, because the light energy transmitted through the fiber is at or below a certain level of a power capable igniting explosive atmospheres [5,6]. In addition, fiber optic cables are not affected by noise and electromagnetic interference common in various industries [6,7]. The system for monitoring defects and damages of reinforced concrete foundations is based on the use of optical fibers of the G.652 standard. The main advantage of the fiber optic strain gauge is that, being distributed over a large area, it allows monitoring the stress-strain relationship of a huge number of points using only one optical fiber cable [3,4,6]. Optical fibers are a transparent core surrounded by a transparent cladding material with a lower refractive index.