Civil Engineering/suction


In calculating pressures in steel warehouse in Roof zones i am getting very small in magnitude +ve net pressures for only negative internal pressure load cases in   roof zones which means pressure acting towards the Rafter. generally there is uplift i believe. but  Is this Reverse case possible?

ANSWER: Dear Arsalan

Both pressure and negative pressure ( uplift)  is possible . Usually negative pressure quantifies between 0.6 and 0.8 of positive pressure. You must assume scenarios to take into account all possibilities. Usually when the wind is not blowing against a surface and passes like getting far from it , it make a negative pressure on it.


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

QUESTION: dear sir,

Is it compulsory/necessary wind Loads on the side walls  also apart from wind ward faces , leeward faces and Roof Zones? and can the sidewall , leeward wall wind pressures be greater than wind ward face?

Dear Arsalan

If the contrary side is inside the building no need to assume suction. if the wall is in free space you need to assume positive and negative same time. In very casual situation negative wind could be worse but normally no ! The abnormal situation could happen in the case of tornados and for special buildings.


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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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