In English | ISSUE 4/2024
Shear Strength in Post-tensioned Beam
The objective of the thesis is clarify shear design according to second-generation Eurocode for concrete structures (EN 1992-1-1:2023) for posttensioned beam and identify good practical solutions for shear design and determination of additional tensile force due to shear. The objective is also gather up the current theoretical knowledge about the shear phenomenon in post-tensioned reinforced concrete structures and shear design models based on the calculation methods of the EN 1992-1-1:2023. Computational analysis is to compare the differences in shear resistance between first- and secondgeneration Eurocodes for concrete structures and NCCI 2/2022. Furthermore, difference in shear resistance between shear reinforced beams with minimum shear reinforcement and beams without shear reinforcement in accordance with EN 1992-1-1:2023 are investigated in different calculation cases.
The thesis consists of a literature review and computational analysis. In a literature review examines prestressed concrete structures, shear resistance of reinforced and posttensioned concrete structures, and also shear design according to various design guidelines. The shear design of the post-tensioned beam is examined in accordance with the first- and second-generation Eurocode for concrete structures and NCCI 2/2022. Computational section are divided into analyses for multiple bridges and individual cases. For multiple bridge analyses, we assess the shear resistance of post-tensioned beams and the additional tensile force due to shear in 12 different simulated double beam bridges with beam models where the determination of the prestressing force has been simplified. The effect of individual factors on the shear strength of post-tensioned beams is investigated in individual analyses.
In post-tensioned concrete beam without shear reinforcement, the shear resistance was found to be greater, when the area of prestressed reinforcement is considered in the values of the effective depth of the flexural reinforcement and reinforcement ratio. In shear reinforced post-tensioned concrete beam, the shear resistance was found to be higher when the area of prestressed reinforcement neglected in the values of the effective depth of the flexural reinforcement and reinforcement ratio. Flow diagrams for shear design were created separately for shear reinforced post-tensioned concrete beam and beam without shear reinforcement in accordance with EN 1992-1-1:2023. The shear resistance of the beam without shear reinforcement was higher according to EN 1992-1-1:2023 than the shear resistance according to the NCCI 2/2022 in the studied cases. The shear resistance of the shear reinforced beam was higher according to the NCCI 2/2022 than EN 1992-1-1:2023 in the studied cases. Overall, shear design with shear reinforcement was found to be more practical for post-tensioned beams according to EN 1992-1-1:2023 in most cases.
