Hybrid I-Girder for Steel Bridges Stiffened with Timber Materials

I-shaped steel girders in bridges are designed to maximize bending resistance by increasing girder height while minimizing web thickness. In Japan, some girders have a web thickness of only 12 mm and a height of 2300 mm, making stiffeners essential to prevent buckling. Previous research has shown that filling the web with concrete enhances resistance to lateral-torsional, torsional, and shear buckling. Building on this concept, this study proposes a hybrid I-girder that uses timber as a stiffening material instead of concrete. Numerical analysis using the Finite Element Method (FEM) was conducted to evaluate the effectiveness of timber stiffening. The analysis considered the anisotropic properties of timber, optimizing fitting techniques and orientation. Results indicate that aligning the grain direction with the girder length significantly enhances bending strength, demonstrating the potential of timber as a stiffening material.