You are here:

Civil Engineering/elastic or cracked deflections?

Advertisement


Question
Good day Engineer,

Kindly clarify this doubt
My Uni taught me elastic design theory is applicable for serviceability limit state particularly to calculate deflections while plastic theory for ultimate limit states . Then why do we find out cracked deflections by modifying stiffness modification factors in ETABS. I believe modifying stiffness factors it means we are doing cracked section analysis for deflections.

BR

Answer
Hi Shahgul,

The plastic theory applies mainly to steel as concrete is essentially brittle, so cracks if subjected to much tension.

Reinforced concrete is partially plastic (or ductile) due to the rebar strain and with proper ductility detailing can sustain quite a bit of deformation (albeit cracked) before failing.

So, to answer you question, yes for deflections the section is considered cracked on the tension 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: 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.

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 •2013: IEK International Conference, Kisumu, Kenya

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 2010)

©2016 About.com. All rights reserved.