In Francophone African countries, the French General Technical Clauses are widely utilized. The clauses only outline the calculation principles for the bending capacity of reinforced concrete beams without providing explicit formulas, and the design of strengthening of existing structures is not involved. Based on the fundamental principles of concrete structures and French standard regulations, the calculation formulas for the bending capacity of reinforced concrete beams were derived. Combined with the assumptions of reinforcement design, calculation formulas for sections strengthened with bonding steel plates were derived. To conclude, an example of the VDN project in Senegal was presented, offering a practical reference for overseas projects.