Research on the Equivalent Span of Hybrid Girder Bridges

Hybrid girder bridges achieve significant improvements in spanning capacity by utilizing lightweight and high-strength materials in the midspan beam segments. To quantitatively describe the enhancement in spanning capacity, this study introduces a simplified analytical model for hybrid girder components, avoiding complex factors, such as span ratio and boundary conditions, typically encountered in previous system-level analyses. The Leq method is proposed based on this new model, utilizing classical beam theory model to calculate and compare hybrid girder components with both uniform and variable cross-sections. The equivalent span increase coefficient, κ, is introduced for the first time, and a simplified formula for its calculation is derived. The calculation errors are kept within 8%, which meets the requirements for preliminary design. Validated through engineering practice, the formula is concise and reveals that κ is solely related to the hybrid ratio, μ, and the linear load ratio, γ. This method provides valuable guidance for the conceptual design and ultimate span prediction of hybrid girder bridges.