Civil Engineering/etabs vs sap


QUESTION: Respected Sir,
I am performing Equivalent static analysis, response spectrum analysis, and non linear static analysis on the same 3d frame in etabs and sap with same material and geometric properties,both are yielding different results but with less difference between them, why they are yielding different results when they belong to same origin or company;
What are the basic difference between both softwares etabs and sap.

ANSWER: Dear Janjua

Could you tell me the percentage of error for some results?

I mean how much is the difference between results?


---------- FOLLOW-UP ----------

QUESTION: Respected Sir,
Thanks for your reply
Following are some reults of a 30 storey model of same material and geometrical properties and no meshing on slabs in both models
         ETABS          SAP2000
modal Time period       4.2922sec         4.40594sec
roof displacement      0.0202m          0.0213m
interstorey drift       0.000085m         0.000074m

with regards
sameer janjua

ANSWER: Dear Sameer

Very good results. The  difference (error) is because of difference of numerical analysis  between 2 softwares which can be different even if they are  from same company. You can follow the worse situation which enriches your calculations.


---------- FOLLOW-UP ----------

QUESTION: Respected sir
Thank you for your reply
Can you elaborate or explain about what numerical analysis difference may be their in both software.; with an example.

With regards
sameer janjua

Dear Sameer

There are several methods of solving matrix problems. When the order of matrix increases to for example 1000x1000 errors increase and a difference appears in results. For low order matrices this error is not significant.


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Babak Esmailzadeh Hakimi


I can answer questions in Structural Engineering, Earthquake Engineering, Project Management and Project Control topics!


I am experienced in the area of earthquake engineering in electrical power industry, i.e. Lifeline Earthquake Engineering. My focus has been on structural seismic design of power installations. Recently I have got involved in project management in the category of constructional engineering.

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Bs degree in Civil Engineering from Ferdowsi University ,1988, Mashhad Iran, Ms degree in Earthquake Engineering, Sharif University of Technology, 1993, Tehran, Iran

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