Following a comment here, I have modified the Composite Beam spreadsheet to correct the stage 1 stresses forces in the reinforcement as listed in Columns 6 and 7, when the tensile face is the top. The output has also been modified to list from top face to bottom (as for the other output), rather than compressive to tension face. The updated spreadsheet can be downloaded from:
The version posted recently at Stress increments in prestressed concrete beams has also been updated, and can be downloaded from:
Composite Design Functions-Stress Inc
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Shouldn’t be there same result for composite section as in Elastic Analysis if we assume same concrete elasticity for stage 1 and stage 2? If there no difference in stiffness between 2 layers than it’s should act as non composite section? I just enter same section as in stage 2 of composite section into Elastic() and I get different depth of NA.
Please check my example:
https://drive.google.com/file/d/1O50L2EzfIBPIs62Ni5lhLMEF9UUH4dwZ/view?usp=sharing
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Ok … looks like my thoughts incorrect since you taking into account existing state of section at 1st stage and account next stage to existing state? Can explain, please, applied loads at stages – not stage 1 + stage 2? It is internal forces at particular stage? Thank you
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I’m not sure what your question is there, but:
All the stage 1 loads, including the prestress applied to the lower section, are applied just to the lower section. The upper section is then poured and the stage 2 loads, including any prestress applied to the upper section, are applied to the combined section, so the stresses will be very different to the loads + prestress being applied to the complete section in one stage.
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