Hambro D-500 Steel composite floor joist system is an advanced up-to-date answer to elevated floor construction challenges. Combining steel joists with poured concrete, the system consists of hybrid concrete/steel T-beams running in one direction and an integrated continuous slab in the other. The bottom chord acts as a tension member in the concreting stage and during the service life of the floor. The web system tying top and bottom chords together consists of bent rods and resists vertical shear in a conventional truss manner. The patented 13 gauge top chord acts as a compression member during the non-composite stage. In the composite stage, the top chord is embedded in the concrete and functions as a continuous shear connector. The concrete slab is reinforced with welded wire mesh. The top chord functions as a high chair, developing negative moment capacity in the concrete slab which behaves as a continuous one-way reinforced slab.