What is the correct stress in the concrete column?

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Homework Help Overview

The discussion revolves around calculating the stress in a concrete column that is reinforced with steel bars, given a specific load and cross-sectional area. The problem involves understanding the relationship between stress, area, and material properties of both concrete and steel.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the stress in the concrete column using the provided load and material properties, while also questioning the accuracy of their decimal placement in the final answer.
  • Some participants discuss the equivalence of different units of measurement for stress, specifically focusing on the conversion between MN/m² and N/m².
  • Others express uncertainty about the physics involved and seek further breakdown of the calculations presented.

Discussion Status

Participants are actively engaging in clarifying the calculations and unit conversions. There is a focus on ensuring that the mathematical reasoning is sound, with some guidance offered regarding standard form and unit equivalence. Multiple interpretations of the results are being explored, particularly concerning the original poster's calculations and the notes they referenced.

Contextual Notes

There is a noted uncertainty regarding the physics concepts involved, as well as potential confusion stemming from standard form representation of numerical values. The discussion reflects a need for clarity on both the calculations and the underlying principles of stress in materials.

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A concrete column is reinforced with steel bars and carries a load of 20t. The overall cross section area of the column is 0.1m^2 and the steel bars accounts for 3% of this area.
Find the stress in the concrete
If the length is 4m< how much does it shorten.

E of steel 200GN/m^2
E of concrete 20 GN/m^2

Load=20*1000=20000*9.81=196200 or 19.6*10^4

Area of concrete =.1*97%/100=.097m^2
Area of steel=.1*3%/100=.003m^2
Area of concrete=.1*97%/100=.097m^2
steel=s
concrete=c

σs/Es=σc/Ec→σs=σc*Es/Ec→σs=σc*200/20→σs=10*σc

F=σs*As+σc*Ac
19.6*10^4=(10*σc*.003)+(σc*.097)
19.6*10^4=σc(10*.003+.097)
19.6*10^4=σc(.127)

19.6/.127=154.3*10^4
σc=154.3*10^4

My question is, the answer I have in my notes is 1.54MN/m^2. Why is my decimal point wrong?
 
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I'm not sure if it isn't. 1.54MN is the same as 1.54 x 10^6. 154.3 x 10^4 is the same as 1.54x10^6
 
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Fineline00 said:
I'm not sure if it isn't. 1.54MN is the same as 1.54 x 10^6. 154.3 x 10^4 is the same as 1.54x10^6

Would be able to break that down more, still don't understand. Thanks
 
I just want to stress I'm not so sure on the physics but I feel it is just a error in standard form

Your notes give you the answer 1.54MN/m2, which is 1.54 Mega nm2 which is 1.54x106 N/m2 or 1,540,000 n/m2

Your answer is 154.3x104 N/m2which is 154.3x10,000 which is 1,543,000 N/m2
 
Fineline00 said:
I just want to stress I'm not so sure on the physics but I feel it is just a error in standard form

Your notes give you the answer 1.54MN/m2, which is 1.54 Mega nm2 which is 1.54x106 N/m2 or 1,540,000 n/m2

Your answer is 154.3x104 N/m2which is 154.3x10,000 which is 1,543,000 N/m2

Thanks
 
Appreciate if someone could check the physics work in my problem.
 
anthonyk2013 said:
Appreciate if someone could check the physics work in my problem.

Anyone thanks
 

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