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in safe program
should i reduced stiffness modifiers (m11-m22 ) when i design tow way slab with beams ?
because the moments on beams differ in two case and of course moments on slab

ANSWER: Dear Rami

I use these modifiers in the case I want to investigate the effect of loose beams or slab or so in some extreme situations. In fact the stiffness of the Rc members will be influenced by cracking effect of the member so using the stiffness modifiers may have real significance. After all I prefer  to have some investigations on the effect of stiffness reduction in some extents and not only to do it because of a definite recommendation of the codes.


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

QUESTION: Thank u very much
So do u prefer to put m11=m22=o.25
When I design two way slab with beams or only I need to modify
Under lareral loads only?
Thank u again for ur reply

Dear Rami

To make a real sense I use m11=m22=1 for non significant loading and for extreme one , I suppose to be the earthquake combined loading I use m11=m22=0.25. But other lateral loading like wind load may be treated moderatly : suppose m11=m22= 0.75. After all , all these investigations are to be made to find critical situations and not a very realistic situation is under consideartion. I want to know the effect of intact stiffness and very disturbed one on foundation behaviour.


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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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