Thank you very much for the reply. Actually I have a perticular problem. I want to find yield moment of hollow circular RC section using ms Excel for a given axial force. NA is located using goal seek to get that axial force. In IS 4998 maximum strain limit in concrete is 0.002 and in CICIND it is 0.003 Es is also different in both codes. So I am asking is yield moment different as per different codes? As you mentioned no FOS is required. Also by adjusting the NA it was found that in many top layers strain in concrete is beyond the limits mentioned in the above code. So in those layers what should be taken as concrete strain?
Q.2 what is in calculation of yield capacity strain in concrete for top few layers is more than maximum value? Do we need to ignore those top layers or maximum strain in all those layers?
You would use a stress-strain relationship for concrete (e.g., Popovics/Thornfeldt/Collins) to find the concrete stress in a layer from the average layer strain. You would set a maximum strain (e.g., strain when concrete crushes, strain when strands rupture). If the strain in a layer exceeded the maximum allowable strain, then you would have failure of the material in that layer. You can see how this would work for the prestressing strands failing in the step down of the moment-curvature relationship on slide 22.
Hello sir, I have few questions please reply q.1: to calculate yield capacity do we need to consider partial safety factor to limit the tensile strain of steel i.e. is it fy/Es or fy/(fos x Es)
No safety factor is needed if you are just analyzing the section (not designing based on ASD/LRFD approaches). You would include a safety factor to the yield strength if you were using Allowable Stress Design. Note however that LRFD is used today for design for prestressed concrete members.
Typically with layered section approach, you would specify properties to different materials and then assign materials to different layers. So you could customize the material properties (e.g., strain limits) for different layers using the approach. I am not sure how much customization you can do in RESPONSE2000 though.
Thank you very much for the reply. Actually I have a perticular problem. I want to find yield moment of hollow circular RC section using ms Excel for a given axial force. NA is located using goal seek to get that axial force. In IS 4998 maximum strain limit in concrete is 0.002 and in CICIND it is 0.003 Es is also different in both codes. So I am asking is yield moment different as per different codes? As you mentioned no FOS is required. Also by adjusting the NA it was found that in many top layers strain in concrete is beyond the limits mentioned in the above code. So in those layers what should be taken as concrete strain?
very useful job can you please provide the matlab code?
Q.2 what is in calculation of yield capacity strain in concrete for top few layers is more than maximum value? Do we need to ignore those top layers or maximum strain in all those layers?
You would use a stress-strain relationship for concrete (e.g., Popovics/Thornfeldt/Collins) to find the concrete stress in a layer from the average layer strain. You would set a maximum strain (e.g., strain when concrete crushes, strain when strands rupture). If the strain in a layer exceeded the maximum allowable strain, then you would have failure of the material in that layer. You can see how this would work for the prestressing strands failing in the step down of the moment-curvature relationship on slide 22.
Hello sir, I have few questions please reply q.1: to calculate yield capacity do we need to consider partial safety factor to limit the tensile strain of steel i.e. is it fy/Es or fy/(fos x Es)
No safety factor is needed if you are just analyzing the section (not designing based on ASD/LRFD approaches). You would include a safety factor to the yield strength if you were using Allowable Stress Design. Note however that LRFD is used today for design for prestressed concrete members.
Q.3, if strain limit in different layers is different will yield capacity is different?
Typically with layered section approach, you would specify properties to different materials and then assign materials to different layers. So you could customize the material properties (e.g., strain limits) for different layers using the approach. I am not sure how much customization you can do in RESPONSE2000 though.