Experiments on a Continuous Composite Truss Bridge with Concrete-Filled Lower Chords

Concrete filled tubular structures have advantages to overcome stability of thin plates and to increase stiffness. A hybrid bridge combining common steel box girders and truss girders was suggested to increase the span length of steel-concrete composite bridges. In negative moment regions, a truss girder has lower chords of concrete filled rectangular steel box section to increase flexural stiffness. A bridge model with span length of 30m was fabricated and static tests were performed to assess the effect of composite chords on the flexural behavior of the girder. Depth of the girder varies from 2.0 m to 3.0 m. Significant reduction of stresses in lower steel chord was observed and measured deflections showed a good agreement with calculated values considering the contribution of infilled concrete. Cracking and crack width of the upper concrete slab were observed and indirect crack control by longitudinal reinforcing bars can be used for the design.