i RELATIONSHIP BETWEEN OUTRIGGER POSITION AND EXTERNAL COLUMNS SIZE IN MINIMIZING BUILDING RESPONSE TO WIND ABDULKAREEM MUYIDEEN OLADIMEJI A project report submitted in fulfilment of the requirements for the award of the degree of Master of Engineering (Civil - Structure) FACULTY OF CIVIL ENGINEERING UNIVERSITI TEKNOLOGI MALAYSIA JUNE 2010
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i
RELATIONSHIP BETWEEN OUTRIGGER POSITION AND EXTERNAL
COLUMNS SIZE IN MINIMIZING BUILDING RESPONSE TO WIND
ABDULKAREEM MUYIDEEN OLADIMEJI
A project report submitted in fulfilment of the
requirements for the award of the degree of
Master of Engineering (Civil - Structure)
FACULTY OF CIVIL ENGINEERING
UNIVERSITI TEKNOLOGI MALAYSIA
JUNE 2010
iii
ACKNOWLEDGEMENT
I would like to acknowledge my supervisor, Dr. Roslida Abd. Samat, for the
guidance and assistance she gave me in understanding the behaviour of tall building
during the course of this thesis.
I also wish to express my sincere appreciation to my dad, Prof. Y.A.
Abdulkareem and my entire family for the support given to me during my course of
study at the University Teknologi Malaysia (UTM).
I am also grateful to Mr. Ibrahim Bamgbopa, Dr. Joseph Dodo and Mr. Zinas
Bako for their efforts during my admission. I would like to thank all my friends, both
at UTM and Nigeria for their moral support and understanding.
iv
ABSTRACT
This research presents the relationship between the position of outrigger and
the size of the external columns in minimizing the building responses to wind.
Outrigger system has been one of the many structural systems in tall buildings used
to reduce the building responses to wind load. The study on the usage of this system
has been given little or no attention to the effect of the size of the external columns to
the optimum position of outrigger. This research involves the position of the
outrigger being varied and the responses: displacement and acceleration being
computed. The procedure is repeated for each different size of the external columns.
This analysis is carried out with the use of structural analysis computer software to
determine the natural frequency of the building and Excel spreadsheet to determine
the responses. The observations from the analysis will provide the conclusion on the
relationship between the size of the external columns and the outrigger location with
respect to the building response to wind.
Keywords: outrigger, wind, column size, tall building, building response.
v
ABSTRAK
Penelitian ini menyajikan hubungan antara kedudukan cadik dan saiz medan luaran
dalam meminimumkan tanggapan bangunan untuk angin. sistem outrigger telah
menjadi salah satu sistem struktur bangunan tinggi banyak digunakan untuk
mengurangkan tanggapan bangunan untuk beban angin. Kajian mengenai
penggunaan sistem ini telah diberikan sedikit atau tidak ada perhatian pada pengaruh
saiz medan luaran ke kedudukan optimum outrigger. Penyelidikan ini melibatkan
kedudukan outrigger yang sedang bervariasi dan respons perpindahan dan percepatan
sedang dikira. Prosedur ini diulang untuk setiap saiz yang berbeza dari medan
luaran. Analisis ini dilakukan dengan menggunakan perisian komputer analisis
struktur untuk menentukan frekuensi alami bangunan dan spreadsheet Excel untuk
menentukan jawapan.Pengamatan dari analisis tersebut akan memberikan
kesimpulan tentang hubungan antara saiz medan luaran dan lokasi outrigger
berhubung
Kata kunci: outrigger, angin, saiz medan, bangunan tinggi, bangunan respon.
vi
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
ACKNOWLEDGMENT iii
ABSTRACT iv
ABSTRAK v
TABLE OF CONTENT vi
LIST OF TABLES ix
LIST OF FIGURES x
LIST OF SYMBOLS xiii
LIST OF APPENDICES xvi
1 INTRODUCTION
1.1 Introduction 1
1.2 Problem statement 2
1.3 Hypotheses 3
1.4 Objective of study 3
1.5 Scope of study 3
1.6 Significance of study 4
2 LITERATURE REVIEW
2.1 Nature of wind 5
vii
2.1.1 Gradient height 7
2.1.2 Design for wind effects 8
2.2 Design criteria 9
2.3 Tall building response to wind affects 10
2.3.1 Wind interference 12
2.3.2 Along-wind response 13
2.3.2.1 Maximum along-wind response 15
2.3.2.2 Maximum along-wind acceleration 16
2.3.3 Across-wind response 16
2.4 The use of outrigger in tall buildings 20
2.4.1 Benefits of outrigger 28
2.4.2 Problems with outriggers 28
2.5 Dampers 29
2.6 Columns in tall buildings 33
3 METHODOLOGY
3.1 Modelling 34
3.2 Building properties 34
3.3 Outrigger positions and columns sizes 35
3.4 Wind speed 36
3.5 Along-wind Response 36
3.6 Along-wind acceleration 37
3.7 Across-wind response 37
4 RESSULTS AND DISCUSSION OF RESULTS
4.1 Introduction 39
4.2 Frequency 42
viii
4.3 Responses 47
4.3.1 Along-wind Response 47
4.3.2 Across-wind Response 52
4.4 Validation of Analysis using Staadpro 57
4.4.1 Analysis using manual calculation 57
4.4.2 Analysis using Staadpro 60
4.5 Calculations 62
4.5.1 Modal mass 65
4.5.1.1 Building with Column size: 1.3m x 1.3m 65
4.5.1.2 Building with Column size: 2m x 2m 66
4.5.1.3 Building with Column size: 3m x 3m 66
4.5.1.4 Building with Column size: 4m x 4m 67
5 CONCLUSION
5.1 Introduction 68
5.2 Variation of outrigger position and column size 68
5.3 Conclusion 69
5.4 Further research 69
REFERENCES 71
APPENDICES 73
ix
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Terrain category and roughness length 8
4.1 Frequency table 37-38
4.2 Along-wind response 42-43
4.3 Across-wind response 46-48
4.4 Mass of Buildings 57
x
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Mean wind profiles for different terrains 7
2.2 Buildings in a row with the wind direction 12
2.2 Computed wind flow pattern around a row of three
square-plan buildings 13
2.4 Vortex formation 17
2.5 A typical wind tunnel 18
2.6 A schematic of a typical open-circuit wind tunnel 18
2.7 Wind on a tall building 20
2.8 braced-core walls with and without outrigger 21
2.9 A typical plan of an outrigger-braced building 22
2.10 An outrigger and belt truss system 23
2.11(a) Building with belt truss as ‘virtual’ as outrigger 24
2.11(b) Force transfer using belt truss 24
2.12 Force transfer using basement as virtual outrigger 25
xi
2.13 Simplified plan of building 26
2.14 Shear wall with outrigger truss 27
2.15 Damped outrigger concept 29
2.16 Tuned mass damper in test fixture 30
2.17 Conceptual detail at outrigger level 31
2.18 Typical layout at outrigger levels 31
2.19 Tendon control mechanism 32
3.1 Plan of the model to be used 35
3.2 Cross-section of Models 38
3.3 Balsa wood model sample 38
4.1 Buildings with various outrigger positions and
columns sizes 41
4.2(a) Along-wind frequency vs. outrigger position 44
4.2(b) Across-wind frequency vs. outrigger position 44
4.2(c) Torsional frequency vs. outrigger position 45
4.3(a) Along-wind frequency vs. column size 45
4.3(b) Across-wind frequency vs. column size 46
4.3(c) Torsional frequency vs. column size 46
4.4(a) Along-wind displacement for different outrigger
positions and different column sizes 50
4.4(b) Along-wind displacement for the same position
of outrigger and different column sizes 50
4.5(a) Along-wind displacement for different outrigger
xii
positions and different column sizes 51
4.5(b) Along-wind displacement for the same position of
outrigger and different column sizes. 51
4.6(a) Across-wind displacement for different outrigger
positions and different column sizes 55
4.6(b) Across-wind displacement for the same position of
outrigger and different column sizes 55
4.7(a) Across-wind acceleration for different outrigger
positions and different column sizes 56
4.7(b) Across-wind acceleration for same position of
outrigger and different column sizes 56
4.8 Free body diagram of the cantilever beam 58
4.9 Cross-section of cantilever beam 58
4.10(a) Core wall 60
4.10(b) Meshed diagram of core wall 61
4.11(a) 3-D Solid core-wall 61
4.11(b) 3-D meshed core-wall 62
xiii
LIST OF SYMBOLS
b - breadth
- mean hourly wind speed factor
- 3-sec gust speed factor
C - turbulence intensity factor
Cfx - mean along-wind force co-efficient
D - diameter of building
E - modulus of elasticity
f - frequency of vortex shedding
Gf - gust factor
gp - peak factor
gQ - peak factor for resonant response
gR - peak factor for resonant response
gV - peak factor for resonant response
h - height
I - moment of inertia
xiv
I - intensity of turbulence
K - wind directionality factor
L - length
L - integral length scale of turbulence
ℓ - integral length scale factor
m1 - modal mass
meff - effective mass
N1 - reduced fequency
n1 - building natural frequency
∅( ) − fundamental modal shape ( ) − rms along − wind acceleration