## 5 Experimental Analysis of the Interaction of Anchor Bolts and Concrete Foundation
### Measurement at Operational Loading  
After a detailed analysis of the condition of the anchor bolts, as well as of the measures taken to relieve the first and the other three bolt threads at the nut location, and also taking into account the previous history of the loading of the anchor bolts, the authors determined the preload forces in the individual anchor bolts as follows:  
* Anchor Bolts No. 1 to No. 24 should be preloaded to an axial force corresponding to 200 kN, which corresponds to a given state of bolts, nuts, and washers when defining a pressure value of 120 bar;
* Anchor Bolts No. 25 to No. 34 should have a preload with regard to the passage of the thread into the shank as well as the flexibility of the supporting structure, and a lower range of operational axial forces of 180 kN, i.e., approximately 110 bar. Dynamometers 1 to 4 were used to measure the time changes of the axial forces in the anchor bolts on the casting pedestal. When selecting the anchor bolts under consideration, effort was made to remove the most, or nearly the most loaded bolts. Based on the above requirements, anchor Bolts No. 8, No. 11, No. 19 and No. 24 were selected, which are located on the outer contour of the supporting structure, therefore the preload value was selected at 200 kN. The forces in the bolts was identified by dynamometers according to Table 2.  
Figure 8 shows the time record of the axial force registered by Dynamometer 3 when tightening the nut to the required preload on Bolt No. 8, with a value of 200 kN. After putting the casting pedestal into testing operation and balancing the strain gauge apparatus connected to the completed measuring chain, the strain gauge measurement of \begin{table}
\begin{tabular}{c c} \hline
**Anchor Bolt** & **Dynamometer** \\ \hline
19 & 1 \\
24 & 2 \\
8 & 3 \\
11 & 4 \\ \hline \end{tabular}
\end{table} 
Table 2: Assignment of dynamometers to anchor bolts. Figure 8: Tightening nut No. 8 according to the required preload of 200 kN registered by Dynamometer 3.  
changes in the axial forces in the anchor bolts began. Unfortunately, the first measurements showed that the cabling on Dynamometer 4 was damaged by the operating personnel. Due to the time duration of the planned outage of the casting pedestal, it was not possible to perform its repair. Therefore, the operational measurement was continued by using only three dynamometers. The first measurements, which were performed only when rotating the casting pedestal without the ladle in the first and second basket, showed that the changes in the axial forces in the bolts did not exceed 6 kN in these measurements. Although these are forces that cause stress in bolts below 3 MPa, i.e., absolutely negligible components in terms of the resulting stress, they testify not only to the condition of the roller track but also to the stiffness of the supporting structure of the casting pedestal. Figure 9 shows the time courses of changes in the axial forces in Bolts No. 8, No. 19, and No. 24 when rotating the casting pedestal without a ladle in Basket 1 and Basket 2, while the beginning of rotation at approximately 2000 s is from the position of Basket 1 from the reserve to the casting position. After a short interruption of the rotation, the rotation continues and the traverse is lifted. It can be seen from the course that the axial force increments do not return completely to zero after the return of Basket 1 to the reserve position (time 5000 s), which may be caused partly by inaccuracies in the return of the traverse to the same position, and also by the changed geometry due to the position of the rollers on the roller track. The following section shows the selected time changes of the axial forces in Bolts No. 8, No. 19, and No. 24. The operator used ladles weighing 70,300 kg (empty) and 241,600 kg (full/tare). Figure 10 shows the time changes of the axial forces when loading the empty ladle into Basket 1 in the reserve position at about 50 s after the start of the measurement.