Wallplate Beams - Lattice Girders remain as reinforcement
The 4-Bar Girders are also used as longitudinal wall plates for heading and bench advances. They serve as bases and fixed points for the height and sides of the arch assembly. At the same time, they can be considered as a statically effective reinforcing of the base beam. The butt connection is rigid in resisting bending and allows easy assembly. The arch spacing is variable.