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Civil Engineering/section modifier in reinforced conc. shear walls

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Expert: - 10/28/2010


Question
QUESTION: dear sir
 I want to know your opinion about assign modifiers and its value on f11,f22,f12,... when we use shell elem. for modeling R.C.Shear wall to act againest earthquake.

until this time i use .35 for f22 & .85 for f12.for others i use 1.
 
thank you

ANSWER: Hi Farid,

This depends on the code you are designing to, but in the Middle East we have been using:

For walls:
m11=m22= 0.7 for uncracked analysis
m11=m22= 0.35 for cracked analysis

For beams:

f11= f12 = f22 = m22 = 0.35

and for slabs:

m11= m12 = m22 = 0.25

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

QUESTION: Dear sir
may I know your opinion about: using hinges(moment release) in r.c.elements such as joints between beams and shear walls ,or joints between beams and columns.

Answer
Hi Farid,

This really depends on the relative stiffness of the beam and the wall or the beam and the column. If the beam is much stiffer than the supporting element, then effectively you will have some yielding and hence a partial hinge forming. You can detail beams with norminal top rebar when they say span into a relatively thin wall (e.g. 500mm deep beam into say a 200mm thick wall),so that this effectively forms a partial hinge. You will never get a 100% moment release unless you use precast beams sitting on a steel or rubber pad, either on walls or columns.

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Arshad Khan

Expertise

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.

Experience

Employment history: 36 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.

Organizations
.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)

Publications
•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

Education/Credentials
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 date)

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