Over the years, several studies have been made for the improvement of the design criteria of stepped beams. However, studies on lateral-torsional buckling of stepped beams located at the midspan have been very limited. Hence, this study aims to evaluate the elastic lateral-torsional buckling strength of doubly symmetric singly stepped I-beam at midspan subjected to pure bending along the entire span. The I-beam measurements and specifications are in accordance with the AISC standards. For the analysis of stepped beams, the parameters α, β and γ are used. In this paper, singly stepped beams are defined as beams having an increased cross section at midspan. The unbraced length used for the simply supported stepped I-beams are 13.59m, 18.12m, and 22.65m while the parameters α, β and γ for the cross section varies from 0.167~0.333, 1.0~1.4, and 1.0~1.8, respectively. To model and perform the analysis for the I-beams, a universal finite element analysis program, ABAQUS, will be used. S4R elements will be used to model the simply supported beams and to check the accuracy of the models guide design specifications are used. The results from the finite element analysis will be shown in tables and plotted into graphs. Based from the obtained results, conclusions and new design guidelines are proposed.

ABSTRACT
 1. Introduction
 2. Finite Element Model
 3. Data and Results
 4. Conclusion
 References

• 랄프(Dept. of Civil Engineering ․ Sangmyung University) | Santos Ralph Raymond
• 임환기(Dept. of Civil Engineering ․ Sangmyung University) | Im Hwan-Gi
• 전형우(Dept. of Civil Engineering ․ Sangmyung University) | Jeon Hyeong-Woo
• 박종섭(Dept. of Civil Engineering ․ Sangmyung University) | Park Jong-Sup