## 3 Results  
The article presents an analysis of the reliability truss tower with the number of repeating sections _lm_ = 6 and topology shown in Figure 2. Towers are designed from S235 steel with the yield strength \(f_{y}\) = 235 MPa. The structure is designed according to the standards [29; 30; 31]. The reliability index is calculated according to the assumption of parallel-serial connections. This assumption is more appropriate than the assumption of serial connections. It is due to taking into account the real performance of the structure. The study investigated the effect of removing each individual element on the reliability structure. The first step, however, involved the assessment of the reliability of the structure in its original state and number of elements being _le_. This analysis includes the following:  
1. Input data (static scheme, load on the structure for the dominant combination, and capacity \(N_{i}\) of individual elements)--shown in Figure 2;
2. Spectral analysis of linear stiffness matrix \(\mathrm{K_{L}}\) (determination the number of KAFMs and MCSEs) --shown in Figure 3;
3. Determination the effect of actions \(E_{i}\) of individual elements--\(\mu_{Ei}\) (Table 2);
4. Checking the effort of individual elements--\(\mu_{E}\)/\(\mu_{Ni}\) (Table 2);
5. Calculation of the reliability index for elements \(R_{i}\) and assessment of the structure reliability. In the case when there is no failure mechanism, the reliability assessment consists in comparing the reliability index of the structure with the required value of the reliability index. The required value of the reliability index was chosen for the RC2 reliability class (50 years reference period). In accordance with the standard [29], \"Three reliability classes (RC1, RC2, and RC3) may be associated with the three consequence classes CC1, CC2, and CC3\". The tower's construction was classified as a structure with the consequence class CC2. This means that \"Medium consequence for loss of human life and economic, social, or environmental consequences are considerable\". The required value for the reliability class RC2 is \(\beta_{\mathrm{EC}}\) = 3.8. The reliability index for parallel-serial system is 4.471. The structure is sufficiently safe, because the reliability index \(\beta\) is greater than 3.8. \begin{table}
\begin{tabular}{c c} \hline \hline
**Random Variable** & **Coefficient of Variation** \\ \hline area of cross section (\(A\)) & 6\% \\ yield strength (\(f_{y}\)) & 8\% \\ modulus of elasticity (\(E\)) & 5\% \\ minimum moment of inertia (\(J_{min}\)) & 6\% \\ length of element (\(L\)) & 6\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Coefficients of variation for random variables describing the capacity of elements. Figure 2: Static scheme of the studied truss tower: (**a**) topology and dimensions, (**b**) vertical load, and (**c**) horizontal load. Figure 3: All of 300 kinematically admissible failure mechanisms for the studied truss tower. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Element** & **Profile** &
\begin{tabular}{c} **Expected Value of the** \\ **Effect of Actions of the** **the** **Effect of Action** **on**  
The next step is to analyze the effect of removing each individual element of the truss tower. The algorithm for the reliability analysis of truss structure with number of elements \(le-1\) is shown together with an example of the effect of element No. 1 removal, as follows:  
1. Input data (new static scheme, load on the structure for the dominant combination, and capacity \(N_{i}\) of individual elements)--shown in Figure 4;
2. Spectral analysis of linear stiffness matrix \(\mathrm{K_{L}}\) for new static scheme (determination of the new number of KAFMs and MCSEs);
3. Determination of the effect of actions \(E_{i}\) for individual elements under new static scheme--\(\mu_{Ei}\) (Table 3);
4. Checking the effort of individual elements for the new static scheme--\(\mu_{Ei}\)/\(\mu_{Ni}\) (Table 3). Figure 4: The new static scheme after the removal of element No.