Structural systems with many components are hard to execute, costly in terms of time and money, and require high caution levels to ensure their composite interaction and optimized performance. Therefore, there is a need to find a simplified and powerful method with reduced construction work and improved actions. This study introduces a modified composite beam construction with a partially encased cellular section and eliminated shear connection parts. The steel sections have wide flanges, cellular webs with systematically arranged circular openings, and encased concrete parts. ABAQUS software was used to numerically assess the extent of the cellular section properties on the flexural behavior of the partially encased cellular beams (PECBs) using different flange thicknesses (3, 6, and 9) mm, and web thickness values (3, 4.5, and 6) mm. The interaction between the two welded horizontal and vertical parts was studied and their effect on the PECBs was introduced. It was found that the new system is innovative with superior properties to ensure favorable strength, lightweight, and ductility characteristics.