![]() ![]() Most of the cracks are in the closed state under dead loads while remaining open under live loads. Especially for partial prestressed concrete structures where cracking is allowed, the cracked sections are usually located at the mid-span of fully or partially PC beams. It imposes significant challenges to the bridge technical state diagnosis and accurate reinforcement. Due to issues such as low design load, long servicing time, indeterminate estimation of effective prestressing decay effect, and overloading, most of the prestressing concrete bridges in service are cracked at varying degrees. Prestressed concrete bridges occupy a relative majority position in bridge engineering because of their advantages, such as simple construction, convenient mold casting, and low cost. It provides a guide for the evaluation and reinforcement of aging bridges. ![]() Compared with the existing methods for estimating the prestress using the mid-span deflection or crack width, the proposed method is more reasonable in theory and calculation. The evaluation results of the total effective prestress are more reasonable than the traditional method based on the steel stress relief hole technique or frequency test results. The determination results of the critical decompression state show that the proposed method (i.e., the stress change rate of tensile rebars-load curve) is more sensitive and reasonable than the traditional stress increment, i.e., load curve method. The proposed method is verified by laboratory tests on beams and numerical analysis and by addressing effective prestress issues of existing simply supported beams. A calculation method for total effective prestress of prestressing strands in the tensile region is derived with the assumption of the plane section and pre-decompression elastomer. In this respect, this research aims at an improved method for the critical decompression moment (DM) test of cracked sections depending on the stress change rate of tensile rebars. Loss of effective prestress and accurate detection of actual stress in existing precast prestressed concrete bridges are two major challenges in the bridge industry. ![]()
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