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Civil Engineering/Max Drift/ Ave.Drfit > 1.2 (NOT OK)

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QUESTION: Dear Sir,

I'm analyzing/design a 27th storey building structure under category D and some issues with my pier(corewall) need your advice.I have checked the axial force ratio, uplifting force and shear wall shear area. It is found that axial force ratio and shear wall shear areas are good. But we have uplifting force in Level 1~2 and the upper levels of the buildings. To eliminate uplifting the force on the bottom levels (i.e., Level 1~2), a solution is to replace/ decrease the wall thickness now its 650mm wall from 800mm. But we still observe big amount tension force (~2000 kN) in upper levels.Any suggestions how I can solve the issue?

Best Regards,
Rari

ANSWER: Dear Rari

No matter if you have uplift. You have to anchor it in foundation unless you have general overturning. Which loading case give you uplift?

Regards
BEH

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

QUESTION: Dear Sir,

Thank you for your reply.

This is the load combination which gave me an uplift (worse)
ULS - 0.764D+1.3(EQx+0.3EQy)Max.

Best Regards,
Rari

ANSWER: Dear Rari

I guess no flaw exists here . Uplift is normally  inevitable when earthquake occurs. The solution is a perfect foundation design. Sometimes I get temptated to use this valuable uplift to dissipate seismic energies in foundation. But I dont suggest this for you. Just anchor the uplift in foundation.

Regards
BEH

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

QUESTION: Dear Sir,

How can you see that" uplift is normally inevitable when earthquake occurs? perfect foundation you mean a Raft foundation? I will make the base support fixed? currently its pinned.

What do you mean anchor the uplift in foundation? how can I do it in my model? or I will do it in detail? if in detail I cannot solve my problem.

Thanks for being patience.

Regards,
Ronald

Answer
Dear Ronald

As I stated before when you design a foundation using the applied load you are doing a perfect design. This is all. Your assumptions are yours. Dont have fear and do your job. The anchoring problem is the same . Whwn you design a foundation considering an uplift you are anchoring the uplift.

Regards
BEH

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Babak Esmailzadeh Hakimi

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

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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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