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Civil Engineering/Special seismic in ETABS


Dear Sir,
What is special seismic. Is ACI OR UBC codes say anything about it and if I don't apply it in Etabs does it make any difference for 12-storyed residential building.
Thank you in advance for your prompt answer

Hi Mohammad,

The special seismic load effects amplify the lateral load by roh factor and vertical component of earthquake as documented in Concrete Frame Design manual for  ACI 318-05 , Chapter 2.

If you do not want to include it, for ETABS v9, in Define > Special Seismic analysis, check the option for “Do not Include special Seismic Load Effects” and click OK. Now rerun the design and the load combinations will be same as what you see in ACI code.

If you are using ETABS v13, the special Seismic Load Effects parameters Rho, SDS have been moved to Design Preferences i.e. Design > Steel Frame Design (or Concrete Frame Design or Wall Design) > View/Revise Preference’s for American standards (AISC 360-05/10, ACI 318/08/11).

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Arshad Khan


I can answer any questions to do with civil and structural engineering consultancy and construction industry in East Africa and the Middle East, and specifically with the analysis and design of reinforced concrete structures. My particular expertise is in the aseismic design and optimisation of tall buildings.


Employment history: 40 years in Construction and consultancy in the UK, Kenya, Tanzania, Uganda, Ethiopia, Eritrea, South Africa, Somalia, Zambia, Austria, Bahrain, Kuwait, Doha and the U.A.E.

.Fellow of Institution of Structural Engineers (UK) .Fellow of Institution of Civil Engineers(UK) .Member of the Institution of Engineers, Kenya .Registered Engineer, ERB, Kenya .Member of the Architectural Association of Kenya (Engineers Chapter) .Chartered Engineer (UK)

•1984: International Conference on the Art and Practice of Structural Design, London •1994: 3rd Int. Kerensky Conference in Structural Engineering, Singapore •2008: International Conference on High-Rise Towers, Abu Dhabi •2013: IEK International Conference, Kisumu, Kenya

BSc, 1st Class Hons, in Building Engineering, University of Bath, UK MSc in Concrete Structures and Technology, University of London. Diploma of Imperial College, UK.

Awards and Honors
•Science Congress Special Award (for 2-seater Hovercraft - 1968) •Institution of Civil Engineers Award for outstanding performance at Bath University (1975) •Concrete Society Postgraduate study Bursary Award (1976) •Consular Representative for British High Commission, Nairobi. (1995 to 1998) •Examiner for Institution of Civil Engineers Professional Interviews, Nairobi. (1997 to 1998) •Branch Representative in Vienna for PI assessment for Inst. of Struct. Engrs. (1999 to 2010)

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