AbstractThe plate-truss composite girder (PTCG) has commonly been used in the design of long-span bridges in recent years. However, most studies regarding flutter stability and related mitigation measures primarily focus on traditional plate-truss separated girders (PTSGs). In this paper, a comparative study is performed to investigate the differences between the flutter characteristics of the PTCG and PTSG via wind tunnel tests and computational fluid dynamic simulations. Upper and lower central vertical stabilizers are applied to the PTCG and PTSG to examine their flutter mitigation effects. The flutter and its mitigation mechanisms are preliminarily explored based on the time-averaged streamlines and flow structures around the truss girder sections. The results show that the PTCG has a better flutter performance at the most unfavorable attack angle of +3° compared with the PTSGs in their service state. The flutter mitigation effect of the upper central vertical stabilizers is much more significant than that of the lower central vertical stabilizers for the investigated truss sections. Moreover, both the upper and the lower central vertical stabilizers have better mitigation effects on the flutter of the PTSG compared with that of the PTCG.