Effectiveness Analysis of the Non-Standard Reinforcement of Lattice Tower Legs Using the Component-Based Finite Element Method

This paper presents an analysis of the effectiveness of the existing reinforcement of steel lattice tower legs made of L-sections by expanding to closely spaced built-up members. Due to the significant differences between the standard assumptions and the existing reinforcement, numerical analyses based on the component-based finite element method (CBFEM) were used to estimate the capacity of the existing structure's tower legs. Geometrically and materially nonlinear stress analysis and linear buckling analysis were performed. The obtained results (stress distribution maps, buckling forms, and corresponding critical forces) were used to modify the geometric parameters of the section of the analyzed tower legs in order to adapt the standard formulas in the calculation procedure. In the analyzed case, distance of the connections between the branches exceeded that indicated in EN 1993-1-1:2005 for the condition concerning the possibility of ignoring the deformation susceptibility in the calculation process. However, it did not result in the separate operation of each branch of the section. Thus, in the case of the analyzed reinforcement, it is possible to neglect the form susceptibility when calculating the buckling resistance of the element. The buckling capacity of the reinforced legs of the tower and the compression capacity of the section of the analyzed structure were calculated according to the method that took into account the results of the numerical analyses. These values are about 35-48% and 30-39% higher, respectively, than the capacity of the unreinforced angle calculated according to EN 1993-1-1:2005 and EN 1993-1-8:2006 standards. Thus, it may be possible to avoid costly and labor-intensive retrofitting of the existing reinforcement to meet the standard requirements. A key issue, and one that is particularly important in light of the lack of standard guidelines aimed at designing reinforcements for telecommunications structures, seems to be the performance of full-scale experimental tests.