Tie bars are essentially deformed high tensile steel bars that are positioned between two solid elements (either between concrete joints or from a concrete edge to a shoulder element). Their design and use are to reduce the chances of movement and separation between elements, and to either prevent or certainly reduce the appearance of transverse cracks.
Construction tie bars while not designed to be load-bearing, do transfer load from one element to another due to their use. However, they should not be used in construction as load-bearing elements.
Tie bars are used in conjunction with tie bar connections, waler plates, and wing nuts within formwork assemblies to maintain positioning and prevent differential deflection.
Within concrete joints, tie bars are used alongside dowel bars and reinforcement to support load transfer across joints and to maintain the elevation of adjacent slabs.