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Double-symmetry I-beams are the most common beam cross-sections in structural building. Because that is simpler to design and analyze steel profiles than single-symmetry I-beams. However, with the advancement of economy, the improvement of the quality of life and the cultural standards, large-scale emergence of various large span bridges, special bridge-type landscapes and viaducts. Single symmetrical I-section is better than Double-symmetry I-section to fairly in line with demand characteristics and material economy. This study chooses different Iyc/Iy ratio sections, 0.229, 0.23, 0.3 and 0.5. Iyc/Iy =0.23 is the change point of the sudden drop of the strength of the compressed airfoil. In study, the section is divided into three sections of plasticity, inelasticity and elasticity for analysis and comparison. Considering the different section sizes. If the value of Lb for a small non-elastic interval is too large, the section with a smaller cross-section will reach the elastic interval. Taking all section conditions Lb into consideration, taking 1.4m as a section will reach the non-elastic interval, if the value of the longer Lb is too small, the section with the larger section does not reach the elastic interval. In study, 10m is taken as the section to reach the elastic interval, orientation the AISC ( 2017 ) specification is used to analyze the I-beam. Symmetrical wing plate cross-sections were increased and reduced. The strength of the cross-sections between the compressed side and the tensioned side was discussed, and a single-symmetric I-section with the best cross-sectional efficiency was proposed.

This study evaluates the variation of the bending moment strength of the single symmetrical and double symmetrical I-beam design. This study compares the use of a double-symmetric I-section with a large, small flange, a single-symmetric I-section with a large compression and large tension flange. The study shows that the four sections have the largest wing strength with double-symmetric I-section, and the inelastic and elastic strengths are similar to those of the single-symmetric I-section, especially the elastic region is almost the same. In the plastic phase, the double symmetrical flanges have a high cross-sectional strength. In the inelastic phase, the intensity of two individual symmetrical sections of the same area is close to a double symmetrical section. The use of a single symmetrical I-beam can be preferred over a double-symmetric I-beam. This study provides a single-symmetric I-beam strength difference analysis, providing users with a variety of options for comparing cross-sections.