International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 6, Issue 4, April (2015), pp. 65-78 © IAEME 65 POSTBUCKLING BEHAVIOR OF WELDED BOX SECTION STEEL COMPRESSION MEMBERS Lilya Susanti 1 , Akira Kasai 2 Yuki Miyamoto 3 1 Graduate School of Science and Technology (GSST), Kumamoto University, 2-39-1 Kurokami Chuo-Ku Kumamoto 860-8555, 2 GSST, Kumamoto University, 2-39-1 Kurokami Chuo-Ku Kumamoto 860-8555, Japan, 3 GSST, Kumamoto University, 2-39-1 Kurokami Chuo-Ku Kumamoto 860-8555, Japan, ABSTRACT Present paper observed the postbuckling behavior of welded box section bridge compression members using static and response analysis. Parametric study using beam and shell varied in width- thickness and slenderness ratio compared with full truss bridge beam model were used. Results indicated that for design based purposes, beam element disregarding initial imperfection factors is still suitable. But for analysis based purposes, which need the capability to perform real structure behavior and to explore the postbuckling regime, shell is the best choice as it can perform more detail compression members behavior and has more severe strength reduction in postbuckling regime, especially. Keywords: Compression Members, Postbuckling Regime, Static Analysis, Seismic Design Methodology, Truss Bridge Structure I INTRODUCTION In the structure with based design purposes, prebuckling phase and maximum buckling load have been considered as the most important parameters. But in the more complex analysis, especially for steel column with thin-walled structures, postbuckling behavior is important to be investigated since in the recent decades, numerical analysis using general finite element software and also experimental study have been able to assess this phenomenon in more detail phases. It is found that the prebuckling, stability and postbuckling behavior of a beam-column depend on the cross section and material properties (area, inertia and elastic modulus), the magnitude of the end restraints and the type and lack of symmetry about the beam-column mid span of the applied transverse loads and initial crookedness [1]. Other studies have shown that the characteristics of postbuckling behavior INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET) ISSN 0976 – 6308 (Print) ISSN 0976 – 6316(Online) Volume 6, Issue 4, April (2015), pp. 65-78 © IAEME: www.iaeme.com/Ijciet.asp Journal Impact Factor (2015): 9.1215 (Calculated by GISI) www.jifactor.com IJCIET ©IAEME