In the French general technical clauses widely used in Francophone African countries, only the calculation principles for the bending capacity of normal concrete sections are provided, with explicit formulas not listed, and the strengthening design of structures is not involved. According to the fundamental principles of concrete structures and French standard regulations, the calculation formulas for the bending capacity of normal concrete sections were derived. On the basis of the assumptions of strengthening design, calculation formulas for strengthening with bonding steel plates were derived. Through practical engineering calculations conducted on the VDN Expressway project in Senegal, the applicability and reliability of the proposed formulas were verified. This study can offer a reference for the design and strengthening of normal concrete sections in similar overseas engineering projects.