Issue 75

P. Grubits et alii, Fracture and Structural Integrity, 75 (2026) 124-156; DOI: 10.3221/IGF-ESIS.75.10

(a) (b) Figure 14: Results for the initial configuration of the 37-bar truss: (a) load–plastic deformation response of the entire structure; (b) load– displacement response at the midspan node of the bottom chord. A closer examination of the presented results, as illustrated in Fig. 9, reveals that following the buckling of the most sensitive top chord members, the structure exhibits a significant loss of stiffness. As a result, both vertical displacement and plastic deformations increase substantially. However, the predefined load level is successfully reached. Furthermore, as shown in Fig. 15, the critical bars experience the largest inelastic deformations, while the remaining members predominantly remain within the elastic range under the load level. Consequently, the final value of the complementary strain energy is determined to be , 28,311.08Nmm p init W  , which is adopted as the reference value 0 p W during the optimization process. Based on this, the threshold for the elasto-plastic design scenario is defined as , 0 0.25 p max p W W  .

(a)

(b) Figure 15: Distribution of (a) vertical displacements and (b) plastic deformations in the initial configuration of the 37-bar truss structure. Comparison between optimization results of the 37-bar truss Following the modeling principles presented in the previous section, three distinct optimization setups are conducted and compared to demonstrate the efficiency and flexibility of the proposed framework. For each setup, 10 independent optimization runs are performed to evaluate the stochastic nature of the GA and assess the reliability of the design methodology. A summary of the three configurations is provided in Tab. 3. It should be noted that the prescribed displacement limit of ,max 40.00mm y U  is consistent with the Eurocode recommendations, calculated as /250 l , where l denotes the span length of the structure.

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