Flexural strength of steel–concrete composite beams reinforced with a prestressed CFRP plate

Experimental studies have reported that externally-bonded carbon fibre reinforced polymer (CFRP) plate can effectively improve the stiffness and strength of steel–concrete composite beams. This paper presents an analytical solution developed to calculate the flexural strength of strengthened composite beams. The solution assumes certain failure modes and varies the locations of the neutral axis. Non-linear finite element (FE) method was also used to calculate the flexural strength of the strengthened composite beams. Experimental results from literature were employed to validate both the analytical and the FE results. The findings show that the FE analyses are in good agreement with the test data in load–deformation curves. The flexural capacity obtained from the closed-form solution and the FE analyses have a reasonably overall agreement with the experimental results, which demonstrates the present closed-form solution is simple yet accurate. The analyses also show the flexural strength is not influenced by the permanent load and the prestressing force when failure results from rupture of the CFRP plate, but the flexural strength reduces with the permanent load and increases with the prestressing force when failure results from crushing of concrete.