The Velocity Lock-Up Device (LUD), also known as a Shock Transmission Unit (STU), is a velocity-sensitive passive protection device for highway and bridge structures. It moves freely during slow displacements (thermal expansion, creep, etc.) and locks instantly under high-speed events (earthquake, strong wind, braking shock), temporarily rigidly connecting the girder and piers for integrated force distribution and enhanced structural safety.
velocity-sensing hydraulic/mechanical locking technology
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: Flow passage closes rapidly / mechanical engagement activates, device locks instantly as a rigid force-transfer component
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Fast response, reliable locking, non-energy-dissipating, only transmits force and coordinates structural behavior
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- Low-speed free movement, high-speed locking for both long-term deformation and extreme loads
- Passive operation without power or control, stable and maintenance-free
Fully sealed, anti-aging, corrosion-resistant, suitable for harsh environments
Long-span bridges, continuous girder bridges, steel bridges
High-pier, large-displacement, seismic-priority bridges
- Velocity-sensitive triggering, different from ordinary dampers or restrainers
- Ultra-fast locking within milliseconds