Common forms of steel box girders/beams include 3 types: Square Column,Rectangular Box Beam, Tapered Box Beam, which are used as main beams, secondary beams, span beams and truss beams. Steel Box Columns common forms are Square Column and Built-up. struction in building and civil engineering. Associate Members are those principal companies involved in the direct supply to all or some embers of components, materials or products. For a rectangular section, f is equal to 1. Plastic centroid and. Metal distribution boxes - large product range in ELMARK. Steel plates are cut to required dimensions using CNC plasma or flame-cutting machines, ensuring precision and minimizing material waste.