Reliability research of serviceability limit states for RC beams strengthened with prestressed CFRP sheets considering prestress loss

Considering the prestress loss and initial load of RC beams strengthened with prestressed CFRP sheets, the formulas of deflection and crack width are put forward. Based on the improved Monte Carlo method and equivalent linear method, the reliability is calculated for deflection and crack width. The reliability results show that when the prestress loss is increased from 500μ Ε to 4000μ Ε, the crack width reliability index is decreased from 7.78 to 0.97, and deflection reliability index is decreased from 4.09 to 3.96. The prestress loss is more sensitive to crack width than to deflection. When the initial load is relatively large, with small CFRP section area and small CFRP elastic modulus, crack width reliability index drops more drastically with prestress loss. To prevent failure of serviceability limit state due to prestress loss, it's suggested that the initial load should be unloaded as much as possible. When the CFRP area is chosen for strengthening, the serviceability limit state should be considered, and the CFRP area can be increased appropriately. The CFRP with large elastic modulus can be adopted to make full use ot its high strength. ©, 2015, Editorial Office of China Civil Engineering Journal. All right reserved.