New approach to calculate prestressed internal load - Direct internal load method

Prestressed loads are internal loads that are generated by the prestressing tendons acting on structural member. They are important parameters in the design and analysis of prestressed structures. According to the characteristics of prestressing tendons, the prestressed loads consist of three portions--the normal force of tendons, anchored force on tendon ends, and the friction between tendon and structure. Based on this observation, the direct internal load method is presented. Using this method, the prestressed load equation and that of the prestress loss due to the friction are obtained, and the self-equilibrium of prestressed loads is proved. After analyzing the difference and the consistency of the direct internal load method and the equivalent load method, it comes to the conclusion that the direct internal load method can demonstrate the regularity of prestressed load acting on the structure, and that the prevalent equivalent load method is perfected by the direct internal load method. The data collected from experiments are close to the results from the numerical simulation by ANSYS using the direct internal load method.