The Lock Up Device System (LUD)
METCO Industries is an exclusive licencee & selling agent for STU/LUDs manufactured by Techstar Inc., USA.

A Lock Up Device (LUD) is a plasto-elastic unit that provides the engineer a simple method of temporarily creating a fixed connection, when desirable, that otherwise would remain as a moveable connection. The device is sometimes referred to as a shock transmission unit or STU. The device is connected to either side of adjoining structures or between elements of structures, where expansion and contraction occur. Upon a sudden dynamic load, the device locks up and transmits the load through the structure. In effect, the device creates a rigid link within a fraction of a second and is modeled as a fixed connection during the shock loading. Once the shock load is removed, the device reverts to its benign influence and the structure behaves in a normal manner. The LUD does accommodate all slow movements associated with a bridge structure such as thermal movement, shrinkage, and creep.

What does a Lock Up Device Lock Up ? ---> Velocity As long as the movement are slow, the STU does not act upon the structure. A large load creates a velocity at which the piston cannot move through the special compound and the device locks. If the force changes direction and again accelerates through the threshold velocity – lock up occurs.

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