Elasticity?

[Waqar Saleem]

do concrete have two moduli of elasticity? as it behaves differently under compression and tension

[Ayesha]

yes, plot stress strain graph for both cases and you will get two different Modulus of elasticity.

[Yasir Saleem]

I am doubtful its not possible as far i think but i will check as well, If its same concrete with same material properties and strength then how its possible i am not sure but i would like some more explanation on this, stress strain are separate properties of a material...

[WR1]

Stress is directly proportion to strain

so Stress=E x Strain

When E is youngs modulus or modulus of elasticity

if the graph is straight line...it means stress is directly proportion to strain so we have one value of E

if the graph changes and stress is no longer proportion to strain ..i mean when it becomes non linear curver then we will have different value of E

so plot the graph when we have tension and when we have compression..and try to see it your self

[Waqar Saleem]

thanx Madam Ayesha , sir Rana and sir Nustian371,madam Ayesha is right and sir Rana as well @Nustian371 sir actually you are right that how it can happen that one material has two moduli but in case of concrete it behaves differently under different loadings i.e. tension and compression also stresses in concrete are different when it is under compression and under tension so does its strain.concrete is a mixture not a uniform homogeneous material like metals.here i have a question that does steel behaves the same way under compression and tension? i am asking this with the view of modulus of elasticity?is tension strain and compression strain for steel are same?as they are different for concrete.

[Yasir Saleem]

I agree with ayesha and Rana they are right,i was thinking same like rana still there is one thing that if we talk about a specific part of concrete section where force is applied so that section will have a compression and tension just simple case so the stress is proportional to strain at point so one modulus at that point but if you take tension is some other part of section and compression on other then you will have two curves so how can you compare them obviously they will have different moduli at that point but how can they be compared as mentioned by waqar as well concrete in not homogeneous so material properties at that point may differ..Rana and Ayesha please correct me if i am wrong ?

[WR1]

i think yasir you are talking about flexure in a simple beam where upper part (above N.A.) is in compression and below the N.A. is tension. But i think Waqar here is talking about AXIAL Tension and AXIAL compression not flexural.

[musht]

For structural purpose concrete is used as compression material only therefore no need to go into E value for tension condition. Until u r required to determine very precisely the strains & deformation behaviour of a stucture element.

[Yasir Saleem]

correct rana but even in axial tension and compression both cases are very difficult to be applied to concrete so when they are applied separately the residual stresses and strains are there in the concrete they will have their effect on the concrete properties....

[WR1]

correct rana but even in axial tension and compression both cases are very difficult to be applied to concrete so when they are applied separately the residual stresses and strains are there in the concrete they will have their effect on the concrete properties....

take the example of column! in normal gemotery of the building, under gravity loads, a column will be under compression! and some times if there is axial tension concrete will also be in tension!

[Ayesha]

For structural purpose concrete is used as compression material only therefore no need to go into E value for tension condition. Until u r required to determine very precisely the strains & deformation behaviour of a stucture element.

yes! Anyhow, if you still cant resist the urge, there are different models available for concrete in tension. Use them only, if you know what are you up to. For day to day stuff, modulus of rupture is there for some number crunching in design office.

[Ayesha]

I agree with ayesha and Rana they are right,i was thinking same like rana still there is one thing that if we talk about a specific part of concrete section where force is applied so that section will have a compression and tension just simple case so the stress is proportional to strain at point so one modulus at that point but if you take tension is some other part of section and compression on other then you will have two curves so how can you compare them obviously they will have different moduli at that point but how can they be compared as mentioned by waqar as well concrete in not homogeneous so material properties at that point may differ..Rana and Ayesha please correct me if i am wrong ?

i think yasir you are talking about flexure in a simple beam where upper part (above N.A.) is in compression and below the N.A. is tension. But i think Waqar here is talking about AXIAL Tension and AXIAL compression not flexural.

Concrete elasticity is always considered for compression. You can do the tests your self on a cube or a cylinder. For the case told by Nustian 371, that would be something like bending, but remember, concrete subjected to bending is designed for compression only.. tension is always ignored. You can never have 2 curves.

[Badar (BAZ)]

For structural purpose concrete is used as compression material only therefore no need to go into E value for tension condition. Until u r required to determine very precisely the strains & deformation behaviour of a stucture element.

Musht has given you most fitting answer.