## 6 Comparisons between the Obtained Costs and Mases of Different Objective Functions  
Comparison of the Obtained Costs between the Direct Cost Optimization and Other Performed Optimizations  
In order to investigate how different objective functions affect the amount of costs of the structures, the optimal costs obtained with the direct cost optimization (DC) are compared with the costs calculated in the mass optimization and in the energy life-cycle cost optimization. Comparative diagrams are presented below. The diagrams in Figure 10 show the achieved costs (EUR/m\({}^{2}\)) of the CFSWIS structures. The diagrams are developed for different objective functions, i.e., for the direct cost optimization (DC), the mass optimization (MASS), the energy life-cycle cost optimization for the energy efficient case (ELCC EEC), the energy life-cycle cost optimization for the energy inefficient case (ELCC EIC), and the energy life-cycle cost optimization for the high energy consumption case (ELCC HEC). Similarly, the diagrams in Figure 11 show the achieved costs (EUR/m\({}^{2}\)) of the CFSIPE structures, while Figure 12 shows the optimal costs of the CFSHEA structures. While the diagrams of the CFSWIS structures are developed for spans of up to 50 m, the diagrams of the CFSIPE structures are drawn for spans of up to 20 m, and the diagrams of the CFSHEA structures refer to spans of up to 25 m.  
Figure 9: Comparative diagrams of the optimal energy life-cycle costs for the high energy consumption case (ELCC HEC) of the CFS structures with welded and standard IPE and HEA sections. Figure 11: Diagrams of the calculated costs of the CFSIPE structures for different objective functions. Figure 10: Diagrams of the calculated costs of the CFSWIS structures for different objective functions. CFSWIS structures: Figure 10 shows that when the mass optimization of the CFS structures is carried out (MASS), the structures are 20% more expensive on average when compared to the optimal costs obtained in the direct cost optimization (DC). When energy life-cycle cost optimization is conducted, the composite structures exhibit 1.65-times higher costs on average for the energy efficient case (ELCC EEC), 2.30-times higher costs on average for the energy inefficient case (ELCC EIC), and 3.50-times higher costs on average for the high energy consumption case (ELCC HEC); all of these costs were compared to the optimal costs of the composite structures calculated in the direct cost optimization (DC). CFSIPE structures: Figure 11 demonstrates that when the mass optimization of the CFS structures is performed, the structures are 15% more expensive on average when compared to the costs obtained in the direct cost optimization (DC). In the case of energy life-cycle cost optimization, the composite structures exhibit 1.45-times higher costs on average for the energy efficient case (ELCC EEC), 1.85-times higher costs on average for the energy inefficient case (ELCC EIC), and 2.60-times higher costs on average for the high energy consumption case (ELCC HEC). CFSHEA structures: Figure 12 shows that when the mass optimization of the CFS structures is performed, the structures are 20% more expensive on average when compared to the costs of direct cost optimization (DC). When energy life-cycle cost optimization is considered, the composite structures exhibit 1.40-times higher costs on average for the energy efficient case (ELCC EEC), 1.75-times higher costs on average for the energy inefficient case (ELCC EIC), and 2.40-times higher costs on average for the high energy consumption case (ELCC HEC). Table 3 shows the cost increment factors related to the calculated costs of the optimizations with different objective functions compared to the optimal costs obtained in the direct cost optimization (DC).