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Civil Engineering/summation of loads at base of the structure at different orientation of the building


QUESTION: Sir, I made a 20 story structure in ETABs, I rotated the same structure at different angles to observe its behavior, but the summation of Dead, Live, Superdead and Roof live loads is coming different for each angle. Can you please suggest its reason. should it be same for all angles? How can I make it same for all angles?

ANSWER: Dear Smilerockerss6o6

It is impossible. Make sure that you dont apply lateral automatic loading like seismic or wind load. If not satisfactory , make a  new model. May be your work on the file has made some conflict inside it.


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

QUESTION: Yes sir I have applied automatic seismic loading as I am designing the structure in zone 2B(UBC 97). Can you please explain how seismic loading can affect this summation of loads at base?

Dear Smile

Then if had just the gravity load you would not see difference in results when you applied a rotation on your structural position. But The application of seismic load will affect the strucure differently in different orientations. The software cant distinguish the skape of the structure to apply the seismic load in direction you like. It apply along global axis. Then the reactions of the structure differ in different directions.


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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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