This research presents an experimental and theoretical study investigating the flexural capacity of built-up steel
cold-formed I-beams strengthened in the hollow web with different materials. Eight built-up cold-formed steel Ibeams
were prepared and experimentally tested. As a control specimen, one was not strengthened, steel shear
connectors strengthened one without materials, and six specimens were strengthened by filling the hollow web
with different materials. The strengthened materials used are wood wastes (Sawdust with epoxy- Sawdust with
polyester), lightweight concrete, normal-weight concrete, High-Strength concrete, and polymer mortar. The
specimens’ method of failure, load at failure, and vertical displacements were recorded. The relationship between
vertical load and deflection at the span’s midpoint has been graphed to analyze the impact of strengthened
materials. Using polymer mortar resulted in the highest capacity, outperforming other materials. Finite element
models of the tested beams were established. Good agreements between experimental and numerical models
were observed. 84-FE numerical models were established to determine the effect of cover plate thickness on
flange width ratios and the height-to-width of the strengthening material. Finally, new equations that calculate
strengthened beam capacity were presented.