finite element results and manual results

[abuelhassan]

Hello ,every body
i wanna get your advice about the difference between sap 2000 results when i solve a sample slab , and when i solve the same slab but by manual solution
the question is are any code explain this issue ! and what about set modifiers option !
thank you

 

[Ron]

The results will vary, for several reasons; however, they should be relatively close...certainly in the same approximation range. If there is great disparity between the results, check your methodology of the manual calcs, then check for accuracy in your modeling approach with the software.

 

[BAretired]

Coefficients for flat slabs vary considerably from one code to another, so it would not be surprising if sap 2000 came up with something substantially different from a given code.

BA

 

[jsha811]

abuelhassan,
You may need to give more details on the sample slab problem you try to solve with SAP2000. Some screenshots will be helpful too.
One point from my experience is if you model the slab with shell elements. Be careful with the boundary conditions. Also if I remember correctly, there is also an element type called plate. Use shell element instead of plate element whenever you can.
Hopefully that helps a little bit.

http://www.structurexpress.com

 

[abuelhassan]

Thank you all,
the differences between sap2000 calculation and manual calculation is about 25% that mean manual calculation give me more safe design
if you can up load a solved sample example for a slab using sap2000 with manual calculation I will be very pleased
and I have attached asap 2000 v 15 file to check my way in solving (I am waiting for your great comments)
thank you all

 

[rapt]

For a start it would depend on what you are analysing, how you define it in SAP and what you mean by a "manual " calculation. If what you have done is as badly defined as your question, then there can be no comparison.

If you are comparing to two way slab tables, they include for a variation in span length between spans, variation in support conditions and a few other variations plus allow for redistribution. They are basically an envelope of solutions.

In SAP, you are analysing a specific set of parameters such as span length, not allowing for possible variations as the two way slab tables do. Are you comparing Mx and My moments or design moments including Mxy effects? There will be a difference of 15-20% between these, especially if it is a flat slab on columns and the more irregular the column grid, the bigger the difference. You must design on the combined Design Moment values, not Mx and My.

 

[abuelhassan]

thank you Mr Rapt