Abstract： In order to study the effectiveness of L-shaped bracings in stability of long-span CFST truss arch bridges, the mechanical behavior and the stability of long-span CFST truss arch bridges are analyzed and compared through theoretical analysis and numerical calculation based on Hejiang River Third Bridge. In addition, the significance of L-shaped bracings in the stability of truss arch bridge is checked by orthogonal test and multi-factor variance analysis methods. The results show that (1) for the topology optimization types of L-shaped bracings, the main arch has the best stability when the K-shaped diagonal bracing is set at the top chord of main arch rib and close to arch foot; (2) compared with the K-shaped, X-shaped or double-cross-shaped bracings, the L-shaped bracings may have less influences on the maximum value of axial force, in-plane bending moment, out-of-plane bending moment, stress and the vertical deformation of the main arch, but they may affect the horizontal deformation of the main arch to some extent. (3) When the parameters are within the reasonable ranges, the replacement of K-shaped, X-shaped or double-cross-shaped bracings with the L-shaped bracings may not significantly reduce the stability of bifurcation buckling and the extreme-value point of the long-span CFST truss arch bridges. Hence, the L-shaped bracings can be chosen by engineers in the stability design of such arch bridges without no special emphasis.
