Experimental Study on Steel‒Concrete Composite Beams Strengthened by Externally Prestressed CFRP Strips

Abstract

This paper mainly studies the mechanical properties of simply supported bridges of steel‒concrete composite structures strengthened with externally prestressed CFRP plates. The introduction of the prestress of the CFRP plate from the support rods can not only apply prestress to the main beam but also provide an upward lifting force at the bottom end of the main beam to reduce the deflection of the original structure. Therefore, the CFRP board is prestressed by the support rods, which can improve the speed and efficiency of reinforcement construction. The effects of the CFRP amount, prestress size, support rods amount and other parameters on the stiffness and bearing capacity of composite beams were studied by a static test of the scaled model. In the flexural test of the tensioned combination beam, by increasing the prestressing level and the number of CFRP plates, the flexural moment of inertia of the combination beam section was effectively improved, the reinforcement effect on the yield bearing capacity and ultimate flexural bearing capacity of the combination beam was obvious, and the reinforced specimens still had good ductility. For the third combination beam, a CFRP plate with a 15% prestressing level and 3 mm thickness was used for reinforcement. The ultimate load carrying capacity of the combined beam was increased by 47.9%; the yield load of the lower flange was increased by 39.8%; and the stiffness in the elastic phase was increased by 21.66%.

Keywords

tension string reinforcement / CFRP plate / steel‒concrete composite beam / active re-inforcement method / flexural bearing capacity

References

[1] Xiao, L.; Wei, X.; Wen, Z.; Li, G. State-of-the-Art Review of Steel-Concrete Composite Bridges in 2019. Journal of Civil and Environmental Engineering 2020, 42, 168-182.

[2] Huang, Q. Design Principles of Steel-Concrete Composite Structures for Bridges, 2 ed.; China Communications Press: Beijing, 2017.

[3] Deng, W. Discussion on the Causes of Diseases and Reinforcement Measures of Steel-Concrete Composite Girder Bridges. People's Transportation 2019, 88+90.

[4] Zeng, L. Experimental and Theoretical Studies on Reinforced Concrete Beams Strengthened with Prestressed CFRP Plates. Tongji University, 2005.

[5] Huang, Y. Study on Maintenance Reinforcement Quality lnspection and Evaluation of Steel-Concrete Composite Bridges. Urban Roads Bridges & Flood Control 2013, 175-179+111, doi: 10.16799/j.cnki.csdqyfh.2013.06.053.

[6] Ministry of Housing and Urban-Rural Development of China. JG/T 167-2016 Carbon Fiber Laminate for Strengthening and Restoring Structures. Standards Press of China: Beijing, 2016.

[7] Deng, Q. Application of CFRP Prestressed Plate in Reinforced Concrete Bridge Reinforcement. TranspoWorld 2021, 100-101+105, doi: 10.16248/j.cnki.11-3723/u.2021.08.046.

[8] Wan, S. Bridge with Prestressed CFRP Platesteel-Concrete Composite Beam Method Study on Strengthening of Experimental and Calculation. Ph.D, Southeast University, 2019.

[9] Kianmofrad, F.; Ghafoori, E.; Elyasi, M.M.; Motavalli, M.; Rahimian, M. Strengthening of Metallic Beams with Different Types of Pre-stressed Un-bonded Retrofit Systems. Composite Structures 2017, 159, 81-95.