In skewed bridges, which condition most directly compromises stability due to torsion?

• A. Inadequate torsional restraint in the bridge detailing
• B. Symmetric bracing and proper rotation continuity
• C. Uniform deck thickness
• D. Excessive dampers

Answer: (A)

In skewed bridges, the load path often creates twisting about the girder axis, so torsional stiffness at connections and supports becomes crucial for overall stability. If the detailing lacks sufficient torsional restraint, the deck and girders can rotate relative to each other under live loads, wind, or seismic forces, allowing the structure to twist and potentially lose stability. This is why inadequate torsional restraint in the bridge detailing is the most direct factor compromising stability under torsion.

The other factors tend to improve or not directly affect torsional behavior: symmetric bracing and rotation-continuous connections increase torsional stiffness; a uniform deck thickness by itself doesn’t ensure torsional restraint; and excessive dampers mainly influence dynamic response rather than causing torsional instability (and can help mitigate it).