TTW is a Maryland design-build firm that uses precast concrete panels to build retaining walls, bridge abutments, and walls for erosion prevention. Each wall consists of three parts:
- The foundation block or footing is cast-in-place, nonreinforced concrete.
- Precast concrete panels are a counterfort type, with concrete braces on the earth side of the wall. Braces are cast integrally with the panel. For tall panels, a precast strut attaches to a hinged connection at mid-height on the brace.
- Rebars protruding from the base of the brace or strut are anchored into a reinforcing cage in the site-cast base slab.