Concrete is a commonly used construction material. One of its deficiencies is a relative weakness and inability to carry tension stress. It is pretty strong in compression, but cracks easily when loaded in tension. One solution to this is prestressing - if the concrete is initially in compression, then tensile loading that comes along later does not cause cracking if the total stress remains in compression (the tension that is added reduces the compression, but does not become a net tension). For one application a concrete member that is 12" square in cross section and L = 20 ft long will be prestressed with four steel strands each As = 0.153 in². Before the concrete is cast, each strand is tensioned to a stress of g = 200 ksi. The strands are located such that the net prestressing force is concentric with the girder centroid. (Steel and concrete have the same center spot) For the completed fabrication scenario, determine the stress in the steel and in the concrete. Esteel- 29000 ksi. Econcrete 4000 ksi 12" 12"

Elements Of Electromagnetics
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32.3

We are trying to solve this problem that reviews a lot of concepts, but I am struggling to get strted and what is the vision I should have. I know the professor said that the 4 cables are treated like only one when considerign the internal forces it will cause...

Problem 32.3
Concrete is a commonly used construction material. One of its deficiencies is a relative weakness and
inability to carry tension stress. It is pretty strong in compression, but cracks easily when loaded in tension.
One solution to this is prestressing - if the concrete is initially in compression, then tensile loading that
comes along later does not cause cracking if the total stress remains in compression (the tension that is
added reduces the compression, but does not become a net tension).
For one application a concrete member that is 12" square in cross section and L = 20 ft long will be
prestressed with four steel strands each As = 0.153 in². Before the concrete is cast, each strand is tensioned
to a stress of g+= 200 kşi. The strands are located such that the net prestressing force is concentric with the
girder centroid. (Steel and concrete have the same center spot) For the completed fabrication scenario,
determine the stress in the steel and in the concrete. Esteel- 29000 ksi. Econcrete = 4000 ksi
12"
12"
Transcribed Image Text:Problem 32.3 Concrete is a commonly used construction material. One of its deficiencies is a relative weakness and inability to carry tension stress. It is pretty strong in compression, but cracks easily when loaded in tension. One solution to this is prestressing - if the concrete is initially in compression, then tensile loading that comes along later does not cause cracking if the total stress remains in compression (the tension that is added reduces the compression, but does not become a net tension). For one application a concrete member that is 12" square in cross section and L = 20 ft long will be prestressed with four steel strands each As = 0.153 in². Before the concrete is cast, each strand is tensioned to a stress of g+= 200 kşi. The strands are located such that the net prestressing force is concentric with the girder centroid. (Steel and concrete have the same center spot) For the completed fabrication scenario, determine the stress in the steel and in the concrete. Esteel- 29000 ksi. Econcrete = 4000 ksi 12" 12"
⠀⠀
12"
12"
Along the way it may help you to complete the following steps:
Sketch system equilibrium and compatibility
Determine the initial elongation of the strands, prior to transfer
Determine the total force, from all the strands, applied to the concrete at the instant of transfer
Determine the amount by which the concrete will shorten at transfer (note, the full force in the strand does
not cause concrete shortening, because the strands are also getting shorter)
Determine the effective prestressing force remaining in the strands after transfer
Determine the average normal stress in the concrete member upon completion of fabrication
Transcribed Image Text:⠀⠀ 12" 12" Along the way it may help you to complete the following steps: Sketch system equilibrium and compatibility Determine the initial elongation of the strands, prior to transfer Determine the total force, from all the strands, applied to the concrete at the instant of transfer Determine the amount by which the concrete will shorten at transfer (note, the full force in the strand does not cause concrete shortening, because the strands are also getting shorter) Determine the effective prestressing force remaining in the strands after transfer Determine the average normal stress in the concrete member upon completion of fabrication
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