Evaluation method for shear strength of pretensioned concrete girder based on refined strut-and-tie model

초록

This paper presents a shear evaluation method designed to address the limitations of existing design approaches for predicting the shear strength of prestressed girders. The proposed shear evaluation method is grounded in the strut-and-tie model (STM) and introduces an optimized STM specifically tailored for prestressed girders, a need not clearly addressed in existing design codes and previous research. Key contributions include a refined approach for determining the node location for harped strands and a method for defining the height of the cross-section STM when a single support is used in prestressed girders that include an end block and two webs, such as box beams. A significant additional departure from conventional STM described in design codes for prestressed girders is the consideration of web capacity and confinement strength through the application of a bottle-shaped STM and a cross-section STM at the bottom flange. Additionally, the proposed shear evaluation method accounts for anchorage capacity and horizontal shear strength, providing a more comprehensive analysis. Comparative analysis with shear test results of pretensioned girders demonstrates that the proposed evaluation method yields more reliable predictions than the conventional STM approach. Furthermore, this method proves more effective for design purposes by significantly reducing the ratio of unconservative predictions compared to conventional STM and sectional design methods suggested in design codes. © 2025 Institution of Structural Engineers

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