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Transcript of Building Design b
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Integrated Civil EngineeringDesign Project
(Building Structure Design)
CIVL 395
HKUST
By : Ir. K.S. Kwan
Date: 3/07
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Content
1. Building Control in Hong Kong
2. Design Criteria
3. Structural Form (Residential Building)
4. Hong Kong Wind Loading
5. Computer Modeling6. Design Example
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STRUCTURAL FORMfor Residential Building
Tower
Podium Structure
Building adjacent to slope
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Lintel beam
To identify the wall as structuralelement and link them together by lintel
beam to provide sufficient lateralstiffness
Slab
Wall
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Slab DesignSlab Design
Concrete gradeConcrete gradeGrade 30 to 35 (too high concrete grade may lead to thermal craGrade 30 to 35 (too high concrete grade may lead to thermal crackckduring large pour of concrete)during large pour of concrete)
Steel reinforcement percentageSteel reinforcement percentageDesign as HKDesign as HK CoPCoP 2004 for structural use of concrete2004 for structural use of concrete
Average steel ratio is around 120~140 Kg/mAverage steel ratio is around 120~140 Kg/m33
Preliminary slab size estimationPreliminary slab size estimation
About 100mm~400mm depending on theAbout 100mm~400mm depending on the span of slabspan of slab ( to minimize( to minimizethe number of different slab thickness, say 2 ~3 types, at typicthe number of different slab thickness, say 2 ~3 types, at typical flooral floor
forfor buildabilitybuildability considerationconsideration
To consider the following loadingTo consider the following loading
Self weightSelf weight
Finishes (domestic area/toilet/kitchen) (25mm to 80mm thick)Finishes (domestic area/toilet/kitchen) (25mm to 80mm thick) PartitionPartition
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Slab is designed asone-way or two waysslab
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Wall DesignWall Design
Concrete gradeConcrete gradeGrade 30, 40, 60 or more is commonly used. By usingGrade 30, 40, 60 or more is commonly used. By using high strengthhigh strengthconcreteconcrete, it can optimize the wall thickness and increase the lateral, it can optimize the wall thickness and increase the lateralstiffness of wall. The concrete grade will also bestiffness of wall. The concrete grade will also be changed along thechanged along theheight of buildingheight of building e.g. from Grade 60 at lower floor to Grade 30 at tope.g. from Grade 60 at lower floor to Grade 30 at top
roof.roof.
TheThe thicknessthickness will bewill be trimmedtrimmed down along the height of building e.g.down along the height of building e.g.from 400 at 1/F and gradually changed to 200 at top floor. Thefrom 400 at 1/F and gradually changed to 200 at top floor. Thethickness will be changed every 10 ~20 storey to minimize thethickness will be changed every 10 ~20 storey to minimize the
disturbance on construction.disturbance on construction.
Steel reinforcement percentageSteel reinforcement percentageDesign as HKDesign as HK CoPCoP 20042004
Average steel ratio is around 100~150Kg/mAverage steel ratio is around 100~150Kg/m33
Preliminary wall size estimationPreliminary wall size estimationGravity LoadGravity Loadby tributary methodby tributary method
Wind LoadWind Loadby simple computer modelby simple computer model
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3-D
Vertical Element Gravity Load Estimation byVertical Element Gravity Load Estimation byTributary Area MethodTributary Area Method
Plan
W2
W1W1
W3
C1
250250 200 26252625
200
3900
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TRIBUTARY AREA METHODTRIBUTARY AREA METHOD
No. of storey = 20
Storey height = 2800
Slab thickness = 150
Beam size = 400x200 (ext.)
Beam size = 450x250 (int.)
Dead Load = 10KPa
Live Load = 3KPa
AssumptionAssumption
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Plan
1266W3
2568W2
2264W1
1686C1
(KN)
W2
W1W1
W3
C1
250250 20026252625
200
3900
TRIBUTARY AREA METHODTRIBUTARY AREA METHOD
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Lintel Beam DesignLintel Beam Design (where linking shear(where linking shearwall together to transmit wind shear force)wall together to transmit wind shear force)
SizeSizeWidth as wall thicknessWidth as wall thickness
Depth controlled by headroom (min.Depth controlled by headroom (min.under side of beam i.e. 2100 at doorunder side of beam i.e. 2100 at doorand 2300 under beamand 2300 under beam
Concrete grade same as floor slabConcrete grade same as floor slabfor easy concrete pour with slab orfor easy concrete pour with slab ormore if requiredmore if required
Steel reinforcement percentageSteel reinforcement percentageDesign as HKDesign as HK CoPCoP 20042004
Average steel ratio is around 120Average steel ratio is around 120~160 Kg/m~160 Kg/m33
Preliminary lintel size estimationPreliminary lintel size estimationWind LoadWind Loadby simple computerby simple computer
model; the size is always controlledmodel; the size is always controlledby wind shear transmission (in someby wind shear transmission (in somecritical case, steel plate will be usedcritical case, steel plate will be usedto replaceto replace r.cr.c. design to enhance the. design to enhance thewind shear transmission)wind shear transmission)
Gravity LoadGravity Loadby tributary methodby tributary method
(not the controlled case)(not the controlled case)
LintelBeam
Steel plate at lintelbeam
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TransferStructure
Podium(Plate Structure)
Tower(Shear Wall system)
Supporting Column
(Rigid Frame)
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Transfer Girder Structure
The behavior is similar to deep beam whenthe wall extending to columns such as case a,
b & c.
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Transfer Plate StructureShear WallStructure atTower above
Transfer Plate
ColumnStructure belowTransfer Plate
Thick plate structure
to support all wallstructures above
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Transfer Plate
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Transfer Structure Design (Plate or Girder)Transfer Structure Design (Plate or Girder)
Design similar toDesign similar to pilecappilecap or beamor beam
Closed column spacing under the transfer structure to allow trusClosed column spacing under the transfer structure to allow truss effects effect
at transfer structure to minimize the deformation of transfer stat transfer structure to minimize the deformation of transfer structureructure
((PrestressedPrestressedtransfer structure is required for large span )transfer structure is required for large span )
Steel reinforcement percentageSteel reinforcement percentage
Design as HKDesign as HK CoPCoP 20042004Average steel ratio is around 240~280 Kg/mAverage steel ratio is around 240~280 Kg/m33
Preliminary size estimation (1.5m ~5m)Preliminary size estimation (1.5m ~5m)
Depend on the spacing of columns and tower loadingDepend on the spacing of columns and tower loading
Gravity loadGravity loadas the wall load transmitted tower load to plate levelas the wall load transmitted tower load to plate level
Wind loadWind loadthe platethe plate behaviourbehaviour as frame structure integrated with columnsas frame structure integrated with columns
belowbelow
Normally, the thickness is controlled by shear stressNormally, the thickness is controlled by shear stress
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Loading from towerincluding:
(P) Axial Load(M) Moment
(V) Shear
Transfer Plate Design
To cater for gravity load andwind load from tower
structure including axial load,moment and shear
The transfer plate with
column below to form a rigidframe structure
All loadings are transmitted
to foundation by shear,moment and axial force.
Podium
Structure
Behavior
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Transfer Plate withPrestressed Tendon
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Building DevelopmentAdjacent to Slope
Retaining structure isrequired for buildingnear the slope
The extent ofexcavation willdepend on the subsoil
condition of slope i.e.Rock / Soil
????
????
???
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Building Developmentnear Slope
Column undertransfer structure
Transfer Plate
Walls at Tower
Large Diameter
Bored Pile Pile Cap
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Retaining Wall Structure
Pile Cap
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Retaining structure forsemi-basement
construction
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Retaining WallStructure with
deep excavationrequired
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Two levels
basement toreduce the deep
excavation
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HONG KONG
WIND LOAD
Wind Load
Assessment Procedure
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Wind Responses of a Building
Static
Dynamic
No movement Wind direction
- Along wind
response
- Cross wind
response
- Torsional wind
response
EquivalentStatic Load
WC 2004
Gust Factor
Method
WC 2004
Literature/ Wind Tunnel Test
WC 2004
Wi L A t P
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Win Loa Assessment Proce ure
(1)
(i) Open frame with significantresonant dynamic response, or
(ii) f natural < 0.2Hz, or
(iii) Significant cross wind /
torsional resonant response
(i) fnatural 5 x Min (B, D); or
H > 100m
(i) fnatural > 1Hz; or
(ii) H
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Buildingheight (H)
Building leasthorizontal dimension(B,D)
B
Building on plan
To determine building
height (H) and width
(B,D)
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h
B
H
b
To define the heightand least dimension
of building
Sec A-A
Sec B-B
A-A
B-B
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Wind Load Assessment Procedure (2)
Calculate Force Coefficients (Cf)
Height Aspect Factor, ChShape Factor, Cs
[Appendix D, p.14~15]
Calculate Force Coefficients (Cf)
Height Aspect Factor, ChShape Factor, Cs
Reduction Factor, RA[Appendix D, p.14~16]
4
Calculate Gust Response Factor (G)
[Appendix F, p.19~21]
2b
Calculate Total Along-Wind Force
F = G. Cf . qz .Az[Eqn (3), p. 4]
Calculate Topography Factor
[Appendix C, p.10~13]
Calculate Design Hourly Mean Wind
Pressure
[Table 2, p.5]
Method 2 Slightly Dynamic Building
Calculate Total Wind Force
F = Cf. qz .Az[Eqn (1), p. 3]
5
Calculate Topography Factor
[Appendix C, p.10~13]
3
Calculate Design Wind Pressure
(3-sec. gust pressure)
[Table 1, p.3]
2a
Method 1 Static BuildingStep
Steps 2 - 5
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Wind Code 2004 Only One Terrain
Open Sea Terrain
Step 2a Design Wind Pressure/ DesignHourly Mean Wind Pressure
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Wind Profiles Below 200m
Wind Pressure Profile Under 200m
0
50
100
150
200
250
0.00 1.00 2.00 3.00 4.00 5.00
Pressure (KPa)
Heig
ht(m)
1983
1983
(Stepwise)
PNAP150
2004
Step 2b Along Wind Dynamic
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The original method was developed by Davenport
(1967) and Vickery (1966 and 1971)
In Wind Code 2004, the equation is simplified to:
(Refer to Wind Code 2004 Appendix F for
description of the other variables)
Step 2b - Along Wind Dynamic
Resonant Response by Gust Factor
Method (1)
SEgBgIG fvh
2
221 ++=
St 2b Al Wi d D i R t
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Dynamic resonant response is dependant on the
magnitude of the fluctuating load as well as its size
(or scale) in relation to the size of the structure
The size reduction factor, S, accounts for the
correlation of pressures over a building and is equal
to
The reduction factor, RA, in Table D3 (p.16) does
not apply to the Gust Factor Method in
Appendix F
+
+
h
a
h
a
V
bn
V
hn 41
5.31
1
Step 2b - Along Wind Dynamic Resonant
Response by Gust Factor Method (2)
h/
b/
representsthe size of the
wind gust
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Step 3 Topography Factor (1)
Wind Code 2004 Speed up ratio adopted from BS6399-2:1995
except that the altitude factor in BS6399-2 wasexcluded
(In BS6399-2, altitude factor is used to adjust
the basic wind speed for the altitude of the siteabove seal level.)
St 3 T h F t (2)
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Step 3 Topography Factor (2)
St 3 T h F t (3)
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Step 3 Topography Factor (3)
St 3 T h F t (4)
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Step 3 Topography Factor (4)
St 3 T h F t (5)
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These examples are taken
from British reference bookbased on British Code. Due tothe different requirements in
British Code and Hong KongCode regarding the idealization
of the hill/slope, the actualhill/slope shall be differentlyidealized under the two Codes.
These examples from Britishwere for illustration only and
the method of idealizing thehill/slope should not be copiedfor application to Hong Kong
Code.
Step 3 Topography Factor (5)
Step 3 Topography Factor (6)
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Step 3 Topography Factor (6)
Step 3 Topography Factor (7)
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Comment: Idealized slope (a) may be more appropriate for Hong Kong Code.
Step 3 Topography Factor (7)
Topography FactorTopography Factor (App. C of HK Wind Code)(App. C of HK Wind Code)
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opog ap y actop g p y ( pp C C )( pp )
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Forces on Buildings1. Total Force on a Building
F = Cf qz Azwhere Cf= force coefficient
qz = design wind pressure at height z
Az = effective projected area of that part of the
building corresponding to qz
2. The effective projected area of an enclosed building shallbe the frontal projected area
3. The effect projected area of an open framework buildingshall be the aggregate projected area of all members on aplane normal to the direction of the wind
4. Each building shall be designed for the effects of windpressures acting along each of the critical directions
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Force CoefficeintsA. For Enclosed Building
a) Cf = Ch x Cs
b) From other international codes accetped byBA
c) For building with isolated blocks projecting
above a general roof level, individual forcecoefficients corresponding to the heightand shape of each block shall be applied.
d) For building composed of similar contiguousstructures separated by expansion joints,the force coefficients shall be applied tothe entire building.
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Height Aspect Ratio Ch
Height Aspect Factor Ch
1.21.210.0
1.4-20.0 and over
1.11.16.0
1.051.054.0
1.01.02.0
0.950.951.0 or less
20041983
HeightBreadth
Remark: Linear Interpolation to obtain intermediate values
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Shape Factors Cs for Enclosed Building
1.33.0 and over
1.12.0
1.01.0 or less
Csb/dPlan Shape
d
b
wind
Remark: Interpolate linearly
Rectangular
b
d
Cs for buildingswith closed
spacing
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Shape Factors Cs for Enclosed Building
wind
Cs for the Respective enclosingrectangular shape in the direction ofthe wind
Other Shapes
0.75
Circular
CsPlan Shape
Note:When the actual shape of a building renders it to become sensitiveto wind acting not perpendicular to its face, the diagonal windeffects and torsional wind effects should be considered
Reduction Factor RA
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Reduction Factor RA
Gusts are the results of eddies and vortices
The speed of gust is a function of its duration
The smaller the size of the gust, the shorter will be its duration and thehigher will be the gust speed
The larger the size of gust, the longer will be its duration and the lower theaverage gust speed
A small gust can only create high wind loading on a small local area of thestructure
The whole structure should be designed with the speed of a gust which isjust big enough to affect the whole structure simultaneously
A 3 second gust can normally engulf a building with frontal area of 300 to800m2, a longer duration gust is required to be effective on the whole ofthe structure
A reduction factor is therefore applied when designing buildings of largerdimensions
(E.C.C.Choi Commentary on 1983 wind codes)
Not applicable for buildings with significant resonant dynamic responsedesigned by using hourly mean wind pressure
Reduction Factor RA for Enclosed
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Reduction Factor RA for Enclosed
Buildings
0.8015000 and over
0.8410000
0.868000
0.8950000.923000
0.961000
0.978001.00500 or less
2004
Reduction Factor RAFrontal Projected Area m2
Note : Linear Interpolation may be used to obtain intermediate values
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Wind Load Case
X & Y directions are commonly accepted
Additional wind direction (e.g. diagonal wind
for Y-shape building) is required For large frontal area building (say >50m),
additional torsional wind load (10% of long
face dimension) is required
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Wind Load Distribution
at Building
Wind Load Calculation as HK CoP
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Wind Load Calculation as HK CoP
(Building is considered as significant resonant dynamic structure)
Wind load
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Wind loadcalculation at each
floor for a building with40 storey (with 3 floorsabove domestic floor)and the building width
is 40.23m
Building structure as
significant resonantdynamic structure \
Sa=topography
factor
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Wind Load Calculation as HK CoP
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Wind Load Calculation as HK CoP
(Building is not considered as significant resonant dynamic structure)
Wind loadcalculation at each
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calculation at eachfloor for a building
with 40 storey (with 3floors abovedomestic floor) andthe building width is
40.23m
Building structure
not considered assignificant resonant
dynamic structure
(Note: Total wind
shear is larger basedon static wind loadapproach for buildingaspect ratio just
greater than 5)
Sa = topographyfactor
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COMPUTER MODELING
Common Structural AnalysisCommon Structural Analysis
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Common Structural AnalysisCommon Structural Analysis
Software used in Hong KongSoftware used in Hong Kong
ETABSETABS
SAP2000SAP2000
SAFESAFE
SADSSADS
GSAGSA STARIIISTARIII
GTSTRUDLGTSTRUDL
PAFECPAFEC
STANSTAN
Tall Building Modelling AssumptionsTall Building Modelling Assumptions
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Tall Building Modelling AssumptionsTall Building Modelling Assumptions
1.1. MaterialMaterialAll structuralAll structuralcomponents behavecomponents behavelinearly elastically.linearly elastically.
2.2. ParticipatingParticipatingComponentsComponentsonly theonly theprimary structuralprimary structural
componentscomponents participateparticipatein the overall behaviourin the overall behaviour
3.3. Floor slabsFloor slabsFloor slabFloor slab
are assumed to beare assumed to be rigidrigidin planein plane unless theyunless theycontain large openingscontain large openingsor are long and narrowor are long and narrow
in planin plan
Only the primary
structuralcomponents are
put in model
Rigid in plane
Tall Building Modelling AssumptionsTall Building Modelling Assumptions
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g g pg g p
4.4. Negligible stiffnessNegligible stiffnesscomponent stiffness ofcomponent stiffness ofrelatively small magnituderelatively small magnitude
are assumed negligibleare assumed negligible
5.5. Negligible deformationsNegligible deformationsdeformations that aredeformations that are
relatively small and of littlerelatively small and of littleinfluence are neglected.influence are neglected.
6.6. CrackingCrackingthe effects ofthe effects ofcracking in reinforcedcracking in reinforcedconcrete members toconcrete members toflexural tensile stresses mayflexural tensile stresses maybe represented by abe represented by areduced stiffnessreduced stiffness
This line should be astraight line in
assumption due to thesmall deformation
How to apply wind loading inHow to apply wind loading incomputer model?computer model?
V
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computer model?computer model?In common building shape
with the rigid diaphragmassumption, the wind loadshould be applied at the
geometry centre of each floor
Windload
appliedat floor
Wind load applied at
centre of frontal area
What can you find inWhat can you find in
computer modeling?computer modeling?
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computer modeling?computer modeling?
Seismic, wind and gravitySeismic, wind and gravity
analysisanalysis
Deformation of buildingDeformation of buildingunder different loadingunder different loading
conditionsconditions
Member force underMember force underdifferent loading conditionsdifferent loading conditions
Deflection of building at topfloor including the X & Y
displacement and Z direction
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d sp ace e t a d d ect o
rotation
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Q & AIf you have any questions about the structural design, pleaseforward email (with your Name and Student ID no.)