Civil Engineering/Piles in ETABS


QUESTION: I have a G+1+Roof Structure in Seismic Zone 3. I have plinth beams below my columns followed by piles (no pile caps). I want to make a model in ETABS so do I have to model piles (like assigning springs etc) or I can just provide hinge or fixed support at base of columns and design the piles separately??
Does the modelling of piles in ETABS affects the superstructure?

ANSWER: Dear Vira

There is no strict method and way to do what you need. You can assume an arrangement of springs underneath of the footing, one of them being the pile model. I don't suggest a fixed or hinged support, but you can try it for more assessment. I can even suggest you to model the whole pile as a laterally supported column. pile modelling may affect the superstructure behavior slightly, not serious , because you design the pile to have more fixed support not less .


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

QUESTION: Please tell me if my approach is right

I have modeled my piles with actual dimensions and placed a hinge support at the base. I have provided spring supports (vertical 20xdia and hoirzontal 10% of vertical springs). I have attached a picture from Atkins Manual.
My pile dia is 8in so I have provided my spring constant as 160 (in Kip-in unit).

So is this approach correct?
Can I also design my piles using this model?

Dear Mustafa

Your approach is ok. I can understand what you made about horizontal and vertical relative  springs stiffness. but I cant say anything about the horizontal stiffness itself because I have to be involved more deeply. For example I don't know anything about the soil characteristics. The pictures you said I don't have it. Please try it again to send me.


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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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