Civil Engineering/Query


Kindly clarify the difference between Top, Extra and Negative reinforcements?

ANSWER: Dear Muhammad

in a typical beam we have 2 layer of bars.

- positive moment bars  or lower bars which are placed in the middle of the beam. These bars are to carry the tensile stress due to positive moment on the middle of the beam.

- Negative moment bars or top bars . They carry the negative moments in support zone i.e. the corners of the beam.

usually engineers do not place the maximum needed bars in all part of the beam due to economical requirements. They place  a minimum bar along the beam and add extra bar where the moment intensity increase more than minimum considered.

I hope this would be enough and clear. Please let me know if you had amore questions.


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

QUESTION: Thanks Sir,

Would You please explain your reply for slab? Actually I am little bit confused.


Dear Muhammad

No difference between a slab and a beam in this matter. You use top bars on corners, lower bars on the bottom. Usually you use a minimum top bars all over the slab and also for the lower bars . The extra bars are needed where you need more than minimum bars. Usually top and bottom bars are installed all over the slab and the extra bars are placed in limited areas. This is because of economical requirements.


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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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