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Civil Engineering/Modellling of footing in etabs


QUESTION: hii sir,

you have said that we can model footings as short columns in etabs, yes it is good to do so, but how can we decide the dimensions of those short columns and what end conditions we should assign them.

ANSWER: Dear Kolloru

First I need to know why you neeed to model a footing as a column. Please make clear.


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

QUESTION: hii sir,

when i neglecting the plinth beams and assigning restrain conditions the ground story columns they start to behave as long columns
so, i have decided to include plinth beams and add footings below them as short columns
please suggest me whether it is feasible or not, why if it is not.
i need to perform pushover analysis and response spectrum analysis on the whole structure.

ANSWER: Dear Kolloru

The dimension of the dummy short column is the actual dimension of the footing but as you are tending to more accuracy you need to model the soil beneath the footing like a spring network.


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

QUESTION: thanks for your reply sir

as you said i am tending to more accuracy, please can you say me what is the effect of plinth beams and footings to the whole structure.
if i will neglect them, their is any kind of problem or not.

and you said that we need to model the soil beneath the structure as a spring network. how we can do this in etabs???

thanks in advance

Dear Kolluru

For normal situation where you are doing an engineering job then you dont need to be so accurate to model the plinth beams and foundation in your structural model. For springs you will need to assign links with appropriate stiffness according to soil subgrade modulus which can be drawn from in field tests or roughly from geotechnical references regarding your soil type.


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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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