Lock-Up Devices

 

Lock-up devices allow unrestricted motion when the bridge structure slowly expands and contracts thermally, yet locks the structural masses together under seismic or wind storm conditions.

The primary purpose of Lock Up Device (LUD) is to provide a temporary rigid link between the deck of a bridge and its supporting abutments and piers so that under fast acting and short duration seismic, traction, braking, or collision forces the load is shared between the supports. Under slow acting thermal, shrinkage, or creep movements the LUD no longer acts as a rigid link and moves with the deck. While the concept, and some early examples of such a device have been in existence for several years, it is only recently that LUD has fully developed the idea into a viable commercial economic proposition.