You are here:

Civil Engineering/Bc value ACI 21.4

Advertisement

Expert: - 1/9/2010


Question
Dear Sir,
ACI 318-05 Eq 21-3 and 21-4 are used for determining the minimum area of transverse reinforcement to be provided for a column.

There is a term called "Bc" which is defined as
cross-sectional dimension of column core, measured center-to-center of confining reinforcement (in.)
Following is worked out for 24 in Column in PCA Notes
= 24 - 2(1.5 + 0.25) = 20.5 in.

Now I have checked out alot but I couldnt find that for a rectangular column what value of Bc shall I use.. for example for a  12x24 inch column I get two value.. one large and other small.. which one to use...

Best Regards.
Muhammad Umar

Answer
Hi Umar,

I have not used this clause, but from first principles I would reckon that the smaller dimension is applicable for rectangular columns as the purpose of restraining rebar is to prevent buckling of the vertical compression rebar, which is likely to buckle outwards at right angles to the 24 inch surface, rather than parallel to that face.

Civil Engineering

All Answers

Answers by Expert:

Ask Experts

Volunteer

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)

©2012 About.com, a part of The New York Times Company. All rights reserved.