As a new sectional form of long-span bridges or super long-span bridge, twin box girders can improve aerodynamic performance

and increase the flutter critical wind speed, but it is also necessary to ensure its stationary aerodynamic stability. The evolution

laws of static force coefficients and stationary aerodynamic stability of twin box girders with different wind fairing forms were

studied. Results show that the drag coefficients of twin box girders with two wind fairing forms may increase with the increase of

slotting rate, and the absolute values of lift coefficients may increase with the increase of slotting rate when solid sectional width

is adopted as the dimensionless standard, which is opposite to the observation when total sectional width is adopted as the

dimensionless standard, and in the latter case, the absolute values of pitching moment coefficients may decrease with the increase of

slotting rate. However, all the variation laws may be affected by the wind attack angles. Variations in symmetry of wind fairings only

change the variation laws of the drag force coefficients with slotting rates. For two calculated models, with the slotting rate, the

variation law of every absolute displacement responses at the mid-span and the variation law of critical wind speeds of stationary

aerodynamic instability of a two box girder bridge with symmetrical wind fairings is completely opposite to each other, while the

variation laws of displacements in all directions with asymmetric wind fairings are basically similar although some distinctions can

still be observed. As a whole, the lowest critical wind speeds of stationary aerodynamic instability for twin box girders with symmetric

wind fairings are generally higher than those with asymmetric wind fairings. The critical wind speeds of stationary aerodynamic

instability may increase with the increase of slotting rate after sectional slotting if the change of structural stiffness is considered, 
and moreover the critical wind speeds may exceed the corresponding values if the change of structural stiffness isn’t

considered.Therefore, it is necessary to consider the change of structural stiffness due to the difference in slotting rates when

analyzing the stationary aerodynamic performance of twin box girder.