design of short columns according to aci 318-11 and bs 8110-97

90 Pages·2016·4.41 MB·English

DESIGN OF SHORT COLUMNS ACCORDING TO
ACI 318-11 AND BS 8110-97: A COMPARATIVE
STUDY BASED ON CONDITIONS IN NIGERIA
A THESIS SUBMITTED TO
THE GRADUATE SCHOOL OF APPLIED SCIENCES
OF
NEAR EAST UNIVERSITY
by
SAMiR BASHIR
In Partial Fulfillment of the Requirements
for the Degree of Master of Science
in Civil Engineering
NICOSIA 2014
Samir Bashir: DESIGNOFSHORTCOLUMNS ACCORDINGTOACI 318-11 AND
BS 8110-97: A COMPARATIVE STUDYBASEDON CONDITIONS IN NIGERIA
Approval ofDirector of Graduate School of
Applied Sciences
We certify that this thesis is satisfactory for the award of the degree ofMasters of
Science in Civil Engineering
Examining Committee in Charge:
Prof Dr Ata Aton, Supervisor, CivilEngineering Department, NEU.
••
Assoc. Prof. Dr. Kabir Sadeghi, Committee Chai
,c:
Asst. Prof. Dr Pinar Akpinar, Committee ember, Civil Engineering Department, NEU.
I hereby declare that all information in this document has been obtained and presented in
accordance with academic rules and ethical conduct. I also declare that, as required by these
rules and conduct, I have fully cited and referenced all materials and results to this work.
Name, Surname: SAMIR BASHIR
Signature:
Date:
ii
ACKNOWLEDGEMENTS
All praise is forAllah, lord of all that exists. Oh Allah, sendprayers and salutations upon our
beloved prophet Muhammad, his family, his companions and all those who follow his path
until the last day.
My profound gratitude and deep regards goes to my supervisor, Prof. Ata Atun for his
guidance and encouragement throughout the course of this thesis. His tireless efforts made
this thesis a success.
My deepest appreciation also goes to my parents, family and friends (whose names are too
many to mention inthis context) who stood by me throughout my life endeavors.
I alsowant to thank the people and government ofKano State, my state under the leadership
ofEngr. Rabi'u Musa Kwankwaso for giving me this rare opportunity to further my studies.
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Dedicated to the loving memory of my late siblings Khadijah and Muhammad, may
Aljannatul Firdaus be their final abode, Amin.
iv
ABSTRACT
In the absence of a national design code, structural engineers in Nigeria use BS 811O, Euro
code 2, ACI 318 and quite a number of other structural design codes for the design of
reinforced concrete structures. The principles and design approaches of these codes differ
from one another. Also, some codes aremore economical than others.
This study compared BS 8110-97 and ACI 318M-11 in terms of the design of short column
with particular emphasis on the area of longitudinal reinforcements required, with the aim of
determining which of the two codes provides the most economic design. The super-structure
of a seven storey reinforced concrete hospital building was modeled and analysed using SAP
2000 program taking into account only dead and live loads and assuming only one scenario
(full) for live loads; the result ofthe analysis was used to design the columns with the aid of
Prokon 32 suite ofprogrammes.
The percentage difference between the areas of steel required by the two codes was
calculated with the BS code as the base line. The average percentage difference for all
columns was found to be about -3% indicating that the ACI 318M-11 code requires less
amount ofreinforcement.
Keywords: Short Columns,Area ofSteel Required, BS 8110-97,ACI318M-ll, Prokon 32
V
ÖZET
Ulusal bir plan tüzüğü olmadığından dolayı Nijerya'daki mühendisler güçlendirilmiş beton
binaların planı için BS 811O, Euro code 2, ACI 318 ve çok sayıda diğer yapısal tasarım
planlarını kullanırlar. Bu planların prensipleri, ilkeleri ve tasarım yaklaşımları birbirlerinden
farklıdır. Aynı zamanda bazı planlar diğerlerinden daha ekonomiktirler.
Bu çalışma bu iki plandan hangisinin en ekonomik olduğunu belirlemek amacıyla özellikle
boylamasına (dikey) güçlendirmeye dikkat çekerek kısa kolon tasarımı bakımından BS
8110-97ve ACI 318M-11 planlarını karşılaştırmıştır. Yedi katlı güçlendirilmiş beton hastane
yapısı model alınmıştır ve sadece ölü (kalıcı) ve hareketli yük dikkate alınarak ve hareketli
yük için sadece bir senaryo kabul edilerek SAP 2000 programı kullanılarak incelenmiştir;
analiz sonuçları Prokon 32 programının yardımıyla kolonları tasarlamakta kullanılmıştır.
İki kolonun gereksinimi olan çelik alanındaki yüzdelik farkı ana hat olarak BS koduyla
hesaplanmıştır. Her kolon için ortalama yüzdelik farkı -3% civarında bulunmuştur. Bu da
ACI 318M-11planının daha az desteğe ihtiyaç duyduğu anlamına gelmektedir.
Anahtar Kelimeler: Kısa kolonlar, çelik gereksinimi olan alanlar, BS 8110-97, AC! 318M­
JJ, Prokon 32
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS ii
ABSTRACT iv
ÖZET
V
TABLE OF CONTENTS vi
LIST OF FIGURES ix
LIST OF TABLES ························ ··············································
X
LIST OF ABBREVIATIONS xi
LIST OF SYMBOLS xii
CHAPTER 1 : INTRODUCTION
1.1 Background ofthe Study 1
1.2 Objectives 1
1.3 Works Done 2
1.4 Guides to the Thesis 2
CHAPTER 2 : BACKGROUND AND LITERATURE REVIEW
2.1 Introduction 3
2.2 Previous Studies 4
2.3 Column 9
2.3. 1 Short Columns 12
2.4 BS 8110-97 15
2.4.1 Limit-States Design 15
2.4.2 Partial Factors of Safety for Materials 16
2.4.3 Partial Factors of Safety for Loı!ds 16
2.4.4 Load Combinations 17
2.5 BS 8110-97 Code Requirements for Short Columns ~ 17
2.5.1 Braced and Unbraced Columns 18
2.5.2 Effective Height of a Column 18
2.5.3 Minimum Eccentricity 19
2.5.4 Minimum Number of Longitudinal Bars in Columns 19
2.5.5 Spacing of Reinforcement 20
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2.5.6 Percentage ofLongitudinal Reinforcement 20
2.5.7 Size and Spacing ofLinks 21
2.5.8 Arrangement ofLinks 21
2.5.9 Concrete Cover to Reinforcement 21
2.5.10 Nominal Maximum Size ofAggregate 22
2.6 Short Column Design According to BS 8110-97 22
2.6.1 Short Axially Loaded Column 22
2.6.2 Short Uniaxially Loaded Columns 24
2.6.3 ShortBiaxially Loaded Columns 25
2.7ACI318M-11 27
2.7.1 Strength Design Method 27
2.7.2 Load Combinations 27
2.7.3 Strength Reduction Factors 28
2.8 ACI 318M-11 Code Requirements for Short Columns 28
2.8.1 Percentage ofLongitudinal Reinforcement 28
2.8.2 Minimum Number ofLongitudinal Bars in Columns 29
2.8.3 Clear Distance between Reinforcing Bars 29
2.8.4 Lateral Ties 29
2.8.5 Vertical Spacing 30
2.8.6 Spirals 30
2.9 Short Column Design According ACI 31
2.9.1 Short Axially Loaded Column 31
2.9.2 Short Uniaxially Loaded Column 32
2.9.3 Short Biaxially Loaded Column 34
2.10 General Climate ofNigeria ~ 38
2.10.1 Climatic Conditions inKano Nigeria 38
CHAPTER3:METHOD0LOGY
3.1 Introduction 40
3.2Geometry ofthe Building 41
3.3Assigning Column ID 42
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3.4Preliminary Design 43
3.4.1 Member Sizing 43
3.4.2Gravity Loads 45
3.4.3 Wind Load 46
3.5 Sizing ofColumns 47
3.6 Structural Analysis 48
3.6.1 Modeling ofthe Structure 49
3.6.2Defining Material and Member Section Properties 49
3.6.3 Defining Load Patterns andAssigning Load Magnitudes 50
3.6.4Running the Analysis 5O
3.7 Method ofDesign 51
CHAPTER 4 : RESULTS AND DISCUSSION
4.1 Comparison ofColumn Design Output.. 53
4.2 Comparison ofArea ofSteel Required For Comer Columns 53
4.2.1 Percentage Difference inArea ofSteel Required For Comer Columns 53
4.3 Area ofSteel Required for Side Columns 55
4.3.1 Percentage Difference inArea ofSteel Required for Side Columns 55
4 .4 Comparison ofArea ofSteel Required for Inner Columns 57
4.4.1 Percentage Difference inArea ofSteel Required for Inner Columns 57
4.5 Discussion ofResults 58
CHAPTER 5: SUMMARY, CONCLUSIONS AND RECCOMMENDATIONS
5.1 Sumınary and Conclusions 60
5.2Recommendations 61
••
REFERENCES 62
APPENDIX 66