Which of the following methods are used to check whether the flexural stresses in a prestressed concrete beam remain within permissible limits at transfer and final stages? Select all the correct option(s).
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For prestressed concrete design, remember that "Magnel's graph" and "Limiting zone" are graphical methods to find valid combinations of prestressing force and eccentricity, while "Load balancing" is a conceptual method that simplifies stress calculations.
Step 1: Evaluate each method. - Limiting zone: Defines the region (Safe Zone) where the tendon profile can be located such that fiber stresses remain within code limits at all stages. Correct. - Magnel's graph: A plot of $1/P$ versus eccentricity ($e$) representing the four stress inequalities (Top/Bottom, Transfer/Service). It provides feasible combinations of $P$ and $e$. Correct. - Load balancing: Prestressing is viewed as an upward force counteracting gravity. The net stresses are checked under balanced and unbalanced loads. Correct. - Hoyer's effect: Specifically refers to the wedge action and bond transfer at the ends of pretensioned wires. It does not check overall flexural stress.
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