TechStar is a worldwide leader in the supply of Shock Transmission Units (STU’s), also known as Lock-Up Devices (LUD’s).

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 LUD. 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.

STU/LUD Design Requirements
Every Seismic Device project is different, the following are details TechStar Engineer’s need to design and quote the Seismic Device for this project.

  •  Rate of expansion and contraction during normal operation
  • Total stroke (mm, in.) of the transmission rod through full range of normal movement
  • Ultimate design force to be transmitted through the LUD
  • Geometry of the surrounding application
  • Design code that is applicable
  • Preference in corrosion protection

Notable Projects:

  • Carquinez Bridge
  • Paksey Bridge
  • Geoga Bridge