## 5 Discussion  
The simulation results represent a general picture of the distribution of settlements in the building plan; they do not take into account local effects from the concentrated load from columns and core walls and also do not detail the horizontal plane exactly where the points of dangerous tensile deformation are located. Since concrete does not work well in tension, the local tension of concrete is fraught with crack formation. WFO observations showed increased relative deformations near the zones of concentrated loads (columns) up to 80 \(\mu\epsilon\) (0.8 mm per 1 m length) in the horizontal plane. In Figure 17, single scattered tensile strain points are located in the immediate vicinity of the column and are explained by the tension of the upper part of the raft. Concrete in the places where the column is supported is subjected to compression because of a point load from the upper floors. The top layer of the raft near the column-raft joint is a subject of deflection. Since the optical fiber is located in the upper layers, it undergoes tension in this place. However, in the middle of the deflection zone, the cable is subjected to compression. Figure 16: Horizontal displacement in the X-direction: (**a**) view of the surface of the raft; (**b**) volumetric model. Figure 17: Strains near point loads (columns). In the middle part of the flight, where the spread load is applied, the raft plain is evenly compressed and leads the compression strain of the fiber optic cable. Similarly, compressive stress occurs in the immediate area of the building core with the increased load from the core walls. The increased settlement (negative displacement in Z axis) of the R building core, with a slight focus on the northern part of the building, is also confirmed by the results of computer simulation in the articles by [PERSON] et al. [1]. [PERSON] et al. [2] presented the results of foundation settlement in computer simulation symmetrically to the contour of the building, finding a maximum in the center with a gradual decrease along the edges. According to [PERSON] et al., in GARP (Geotechnical analysis on raft and piles) simulation the maximum settlement of the core was 39.6 mm, and the minimum was in the surrounding columns, at 13.4 mm (Figure 1). So, the differential settlement between the core walls in the middle and the columns by the perimeter of block R is 26 mm, and the distance in horizontal plane is 26.31 m. The values of tensile strain in the horizontal plane are negligible at less than 1 \(\mu\)e.  
The results of FLAC 3D simulation program (Figure 2) show the core of the building reaches the settlement of 37 mm in the raft surface level. The least settled column around the core gains 14 mm of the settlement. So, the differential settlement is 23 mm, and the distance between the core and the least settled column is 20.25 m. With such values of settlement difference, the tensile strain in the horizontal plane in the upper layer of concrete would be less than 1 \(\mu\)e (0.01 mm per 1 m length). However according to SHM, with fiber optic measurement tensile strains with the values varying between \(-\)20 to \(-\)40 \(\mu\)e, compression from +20 to +40 \(\mu\)e near the walls of the core was registered. Fiber optic cable measures the actual data of the concrete strain exactly in coordinates in the horizontal plane; nevertheless, the pre-simulated modelling shows the most appropriate location for laying the fiber optic cable for further measurement. The simulation shows the overall picture of the settlement of buildings in the plan and omits local effects from the concentrated load of the columns. In the considered case, the fiber optic cable layout was placed according to the results of the preliminary simulation to cover the areas expected to have the most subsidence. The results of the fiber optic monitoring were aimed at determining areas at risk of cracking in concrete and not at measuring the settlement.