Calculation of Additional Internal Forces in Post-Tensioned Prestressed Concrete Frame Columns Based on Equivalent Lateral Stiffness

The additional internal forces in vertical members caused by prestressed tendons are typically overlooked in the design of post-tensioned prestressed concrete. A calculation method for additional internal forces in single-story multi-span prestressed concrete frame columns based on equivalent lateral stiffness is proposed in this paper. The slope-deflection equation for the bar element was presented using Timoshenko beam assumptions, taking into account the influence of shear and bending deformations. Subsequently, the concept of equivalent lateral stiffness and calculation equations were proposed. On this basis, the equations of the third shear and third bending moment for single-story multi-span prestressed frame columns were established. Furthermore, applying engineering examples, the method in this study was verified by ABAQUS software and previous methods. The results show that theoretical values and FEA results are in good agreement. Compared to previous methods, the method in this paper is more accurate and widely applicable. In addition, the stretching plan has a significant path effect and time-varying effect on the interlayer distribution of the third moment. It should be considered at the building stage to check the calculation of the frame column.

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