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Civil Engineering/Hollow concrete blocks in Ribbed slabs


QUESTION: Respected Hakimi,
There is a certain type of ribbed slabs that we use hollow concrete blocks to fill in between the ribs before casting the slab. Is this ok in terms of seismic performance or you believe the blocks will be left out during earthquakes.

ANSWER: Dear Abdulhakeem

Using fillers like blocks influences the economical aspect of the project and also will lead to a lighter weight for the slab which is crucial in earthquake case. Then I can say that I am for using blocks something in ribbed slabs. For sure I tend to have lighter blocks or filler materials to keep the weight of the slab lighter.


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

QUESTION: Thanks a lot,
But my question is related to the possibility that these concrete hollow blocks may slip or go out of the slab and fall on the ground during earthquakes. Is this a possibility. Are there any studies or research about that.

Dear Abdulhakeem

It is probable in some cases that blocks fall down, but usually the cohesion between concrete and the blocks doesn't allow such a damage. For special cases of blocks with very smooth surface the probable scenarios shall be investigated by the engineer. As a whole this is not a known mode of damage in earthquakes.

I suggest you to make little holes in blocks to make interlock between concrete and block, in the case you would be anxious according to your assessments.


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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.

Sinam Consulting Engineers Co.

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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