Embed Size (px)
Citation preview
High Rise Structures
Contents 1. Introduction to High Rise Building Design ...................................................................................................... 9
1.1. Introduction ............................................................................................................................................ 9
1.2. Definition of tall buildings ....................................................................................................................... 9
1.3. Structural Design Criteria ........................................................................................................................ 9
1.4. Features of High Rise Design ................................................................................................................... 9
1.4.1. Loading ............................................................................................................................................ 9
1.4.2. Key Issues ........................................................................................................................................ 9
1.4.3. Core optimisation ............................................................................................................................ 9
1.4.4. Floor System .................................................................................................................................... 9
1.5. Designing for Full Life Design ................................................................................................................ 10
1.5.1. Life-cycle costing ........................................................................................................................... 10
1.5.2. Importance of buildability and construction speed ...................................................................... 10
1.6. Functional Requirements ...................................................................................................................... 10
1.6.1. Factors for a successful building ................................................................................................... 10
1.7. Basic Elements ...................................................................................................................................... 10
1.8. Basic Planning Considerations .............................................................................................................. 11
1.8.1. Mechanical and electrical systems................................................................................................ 11
2. Introduction to FEM Analysis ........................................................................................................................ 11
2.1. Finite element discretisation ................................................................................................................ 11
2.2. Element Geometry Preferences ............................................................................................................ 12
2.3. Symmetry and Anti-Symmetry conditions ............................................................................................ 12
2.4. General Rules of Thumb ........................................................................................................................ 13
3. Loads and Design Criteria for High Rise Buildings ......................................................................................... 13
3.1. Structural design criteria ....................................................................................................................... 13
3.2. Stability.................................................................................................................................................. 13
3.2.1. Overturning ................................................................................................................................... 13
3.3. Strength ................................................................................................................................................. 13
3.4. Serviceability ......................................................................................................................................... 14
3.4.1. Deflection criteria.......................................................................................................................... 14
3.4.2. Measurement of deflection .......................................................................................................... 14
3.5. Foundation Movement or Rotation ...................................................................................................... 14
3.6. Dynamic Motion .................................................................................................................................... 14
3.7. Vertical Loading (G and Q) .................................................................................................................... 15
3.7.1. Magnitude of loadings .................................................................................................................. 15
3.7.2. Live load reduction ........................................................................................................................ 15
4. Gravity Load Resisting Structural Systems (GLRSS)....................................................................................... 15
4.1. Analysis treatment for GLRSS................................................................................................................ 15
4.1.1. Desirable features of floor systems .............................................................................................. 15
4.1.2. Functional considerations for the design of floor systems ........................................................... 15
4.1.3. Diaphragm action .......................................................................................................................... 16
4.2. Design criteria for floor systems ........................................................................................................... 16
4.2.1. Design for strength ........................................................................................................................ 16
4.2.2. Design for deflections ................................................................................................................... 16
4.2.3. Design for dynamic motion ........................................................................................................... 16
4.3. Types of floor systems .......................................................................................................................... 17
4.3.1. General trends in floor systems .................................................................................................... 17
4.4. Framing systems ................................................................................................................................... 17
4.5. Columns ................................................................................................................................................ 17
4.5.1. Types of columns .......................................................................................................................... 18
4.6. Transfer structures ................................................................................................................................ 18
5. Finite Element Analysis (FEM) ....................................................................................................................... 18
5.1. Overall Building Process ........................................................................................................................ 18
5.2. Building systems .................................................................................................................................... 18
5.2.1. Physical structural system ............................................................................................................. 18
5.3. Elements ................................................................................................................................................ 18
5.3.1. 2D Plane Stress Element ............................................................................................................... 18
5.3.2. 2D Plane Strain .............................................................................................................................. 18
5.3.3. Plate/shell elements ..................................................................................................................... 19
5.4. Structural systems ................................................................................................................................. 19
5.5. Structural Analysis ................................................................................................................................. 19
5.5.1. Actions and responses .................................................................................................................. 19
5.5.2. Modelling ...................................................................................................................................... 19
5.5.3. FEA and FEM ................................................................................................................................. 19
6. Load Distribution to Lateral Load Resisting Structural Systems (LLRSS) ....................................................... 19
6.1. Measuring Lateral Loads (AS 1170) ....................................................................................................... 19
6.2. Direction of lateral loads ....................................................................................................................... 20
6.2.1. Factors dictating force directions ................................................................................................. 20
6.3. Wind Loads ............................................................................................................................................ 20
6.4. Earthquake Loads .................................................................................................................................. 20
6.5. Objectives at concept stage .................................................................................................................. 20
6.6. Distribution of lateral loads to individual elements for 2-D analysis .................................................... 20
6.6.1. Assumptions .................................................................................................................................. 20
6.6.2. Procedure ...................................................................................................................................... 21
7. Lateral Load Resisting Structural Systems (LLRSS) – Part 2........................................................................... 21
7.1. Transferring lateral loads ...................................................................................................................... 21
7.2. Structural Systems ................................................................................................................................ 21
7.3. Use of Structural Systems and Building Height ..................................................................................... 23
7.3.1. Concrete ........................................................................................................................................ 23
7.3.2. Steel ............................................................................................................................................... 23
8. Earthquake Induced Loading (Part 1)............................................................................................................ 23
8.1. Earthquake characteristics .................................................................................................................... 23
8.2. Measuring earthquake intensity ........................................................................................................... 24
8.2.1. Moment Magnitude Scale (𝑴𝒘/𝑴𝑴𝑺) ....................................................................................... 24
8.3. Earthquake Analysis Methods ............................................................................................................... 24
8.4. AS 1170.4-2007 Procedure ................................................................................................................... 24
8.4.1. Importance level ........................................................................................................................... 24
8.4.2. Annual probability of exceedance (P) and probability factor (𝒌𝒑) ............................................... 25
8.4.3. Hazard Factor (Z) ........................................................................................................................... 26
8.4.4. Subsoil class ................................................................................................................................... 27
8.4.5. Selection of earthquake design categories ................................................................................... 27
8.4.6. Earthquake design ......................................................................................................................... 28
8.5. Equivalent Static Analysis (Section 6 – EC2).......................................................................................... 28
8.5.1. Seismic weight ............................................................................................................................... 29
8.5.2. Torsional effects ............................................................................................................................ 29
8.6. Vertical Distribution of Lateral Loads .................................................................................................... 29
8.6.1. Natural period of vibration (T) ...................................................................................................... 29
8.7. Dynamic Analysis Method (Section 7 – EC 3) ........................................................................................ 30
8.7.1. Effective modal mass .................................................................................................................... 30
8.7.2. Summation of modal contributions .............................................................................................. 30
8.7.3. Elastic modal dynamic analysis method ....................................................................................... 30
8.8. Centre of stiffness vs. centre of mass ................................................................................................... 30
9. Introduction to SpaceGass ............................................................................................................................ 31
9.1. Key features .......................................................................................................................................... 31
9.1.1. Flexible grid systems ..................................................................................................................... 31
9.1.2. Floor diaphragms .......................................................................................................................... 31
9.1.3. Object based modelling ................................................................................................................ 31
9.2. Integrated element design .................................................................................................................... 31
9.2.1. Design of steel beams and columns .............................................................................................. 31
10. Computer Applications for High-Rise Design ............................................................................................ 32
10.1. Global analysis vs. element design.................................................................................................... 32
10.1.1. ETABS ............................................................................................................................................ 32
10.1.2. SAFE (CSI) ...................................................................................................................................... 33
10.1.3. Plaxis (2D and 3D) ......................................................................................................................... 33
10.1.4. Building Information Modelling (BIM) .......................................................................................... 33
10.1.5. Autodesk Revit and Robot............................................................................................................. 33
10.2. Interpreting results from a global model .......................................................................................... 33
11. Wind Loads for High-Rise Building Design ................................................................................................ 33
11.1. Ultimate and Serviceability Limit States ........................................................................................... 33
11.2. Aerodynamic Shaping ....................................................................................................................... 33
11.3. Types of Wind Design ........................................................................................................................ 35
11.4. Design Criteria ................................................................................................................................... 35
11.4.1. Serviceability ................................................................................................................................. 35
11.5. Wind modelling to study effects ....................................................................................................... 35
11.6. Wind-related problems ..................................................................................................................... 36
11.6.1. Pedestrian comfort ....................................................................................................................... 36
11.7. Code Approach to Wind Design ........................................................................................................ 36
11.7.1. Static analysis ................................................................................................................................ 36
11.7.2. Dynamic response factor .............................................................................................................. 37
11.7.3. Cross-wind forces .......................................................................................................................... 38
11.7.4. Cross-wind moment ...................................................................................................................... 38
11.7.5. Peak along-wind acceleration (for serviceability) ......................................................................... 38
11.7.6. Cross-wind acceleration (for serviceability) .................................................................................. 39
11.8. Types of Damping Systems ............................................................................................................... 39
11.9. Comfort criteria ................................................................................................................................. 39
11.9.1. Human perception levels .............................................................................................................. 39
11.9.2. Horizontal acceleration criteria for occupancy comfort in buildings ............................................ 39
11.10. Wind tunnel testing ........................................................................................................................... 40
11.11. Interference ...................................................................................................................................... 40
12. Wind Loading Example – Low Rise Building .............................................................................................. 40
12.1. Wind Speed ....................................................................................................................................... 40
12.1.1. Wind Direction Multiplier (𝑴𝒅) .................................................................................................... 40
12.1.2. Shielding multiplier (𝑴𝒔) .............................................................................................................. 41
12.1.3. Topographic Multiplier (𝑴𝒕) ......................................................................................................... 41
12.1.4. Terrain/height multiplier (𝑴𝒛, 𝒄𝒂𝒕) .............................................................................................. 41
12.1.5. Site Wind speed (𝑽𝒔𝒊𝒕, 𝜷) ............................................................................................................. 41
12.2. Aerodynamic Shape Factor (𝐶𝑓𝑖𝑔) ................................................................................................... 41
12.2.1. North Direction – external pressures ............................................................................................ 42
12.2.2. North Direction – Internal pressures ............................................................................................ 42
12.3. Dynamic Response Factor (𝐶𝑑𝑦𝑛) .................................................................................................... 42
13. Wind Loading Example – Low Rise Building .............................................................................................. 43
14. Construction Techniques for Tall Buildings ............................................................................................... 43
14.1. Construction of High-Rise Buildings .................................................................................................. 43
14.2. Cost Breakdown of Tall Buildings ...................................................................................................... 43
14.2.1. Construction optimisation ............................................................................................................ 43
14.2.2. Design for construction speed ...................................................................................................... 44
14.3. Core Construction ............................................................................................................................. 44
14.3.1. Efficiency of Core Construction ..................................................................................................... 44
14.3.2. Steel vs. concrete cores................................................................................................................. 44
14.4. Floor Construction............................................................................................................................. 44
14.4.1. Precast floors................................................................................................................................. 44
14.4.2. Composite floors ........................................................................................................................... 44
14.5. Column Construction ........................................................................................................................ 45
14.5.1. Composite columns ....................................................................................................................... 45
14.6. Key factors of structural systems ...................................................................................................... 45
15. Foundations for High-Rise Buildings ......................................................................................................... 45
15.1. Basic Requirements ........................................................................................................................... 45
15.1.1. General considerations ................................................................................................................. 45
15.2. Pad Footings ...................................................................................................................................... 45
15.2.1. Design process .............................................................................................................................. 45
15.2.2. Contact pressures.......................................................................................................................... 46
15.2.3. Shear of pad footing ...................................................................................................................... 46
15.2.4. Flexural design .............................................................................................................................. 47
15.3. Combined Footings ........................................................................................................................... 47
15.3.1. Design considerations ................................................................................................................... 47
15.3.2. Use of combined footings ............................................................................................................. 47
15.4. Raft Foundations ............................................................................................................................... 48
15.5. Mat foundations................................................................................................................................ 48
15.6. Piled Foundations .............................................................................................................................. 49
15.7. Piled Raft Foundations ...................................................................................................................... 49
16. Earthquake Loading Example – High Rise Building ................................................................................... 49
16.1. Seismic Mass ..................................................................................................................................... 50
16.2. Equivalent Static Analysis .................................................................................................................. 50
16.2.1. Distribution of base shear ............................................................................................................. 50
16.2.2. Torsional effects ............................................................................................................................ 51
16.3. Dynamic Analysis – response spectrum analysis .............................................................................. 51
16.3.1. Modes of vibration ........................................................................................................................ 51
16.3.2. Modal combination of base shear ................................................................................................ 52
16.4. Drift ................................................................................................................................................... 52
16.4.1. Storey drift determination ............................................................................................................ 52
16.4.2. Inter-storey drift ............................................................................................................................ 52
16.5. Performance-Based Seismic Design (PBSD) ...................................................................................... 52
16.5.1. Framework proposed by SEAOC (1999) for performance based seismic design .......................... 52
16.5.2. Earthquake detailing ..................................................................................................................... 53
17. Tall Building Design for Fire....................................................................................................................... 54
17.1. Structural Design and Fire ................................................................................................................. 54
17.1.1. Twin Towers .................................................................................................................................. 54
17.1.2. NYC Building Code ......................................................................................................................... 55
17.1.3. Lessons learned ............................................................................................................................. 55
17.2. Egress difficulties ............................................................................................................................... 55
17.3. Key findings for very tall buildings .................................................................................................... 56
17.3.1. Fire Safety in Australia .................................................................................................................. 56
17.4. WTC 5 ................................................................................................................................................ 56
17.5. WTC 7 ................................................................................................................................................ 56
17.5.1. WTC active systems ....................................................................................................................... 57
17.6. Buildings and Fires ............................................................................................................................ 57
17.6.1. Role of barriers .............................................................................................................................. 57
17.6.2. Prescriptive codes ......................................................................................................................... 57
17.6.3. Fire Resistance Test ....................................................................................................................... 57
17.6.4. Fire Resistance Level (FRL) Ratings ............................................................................................... 58
17.6.5. Engineering Judgement ................................................................................................................. 58
17.7. Calculating Fire Resistance ................................................................................................................ 58
17.7.1. Real fires ........................................................................................................................................ 58
17.7.2. Ingberg’s Approach ....................................................................................................................... 58
17.8. Fire Record (1970 – 2002) ................................................................................................................. 60
17.9. Structural Performance (Equivalent Time) ....................................................................................... 60
17.10. Developing a Fire Model ................................................................................................................... 60
17.10.1. SFPE Standard on calculating fire exposures to structures ....................................................... 61
17.11. Material behaviour ............................................................................................................................ 61
17.11.1. Structural behaviour ................................................................................................................. 62
17.12. Summary of Fire Engineering ............................................................................................................ 62
17.13. Important Societies/Groups for Fire Safety ...................................................................................... 62
18. Wind Accelerations ................................................................................................................................... 62
18.1. Acceleration for serviceability (Appendix G) ..................................................................................... 62
18.2. Damping ratio (Section 6.2) .............................................................................................................. 62
18.3. Peak Along-Wind Acceleration .......................................................................................................... 63
18.4. Peak Cross-Wind Acceleration .......................................................................................................... 63
18.5. Human Perception of Motion ........................................................................................................... 64
19. Concrete Pumping ..................................................................................................................................... 64
19.1. Pumps ................................................................................................................................................ 65
19.1.1. Challenges of pumping in high-rise buildings ............................................................................... 65
19.1.2. Pumping height versus pressure ................................................................................................... 65
19.2. Pump-ability ...................................................................................................................................... 65
19.2.1. Properties affecting pump-ability ................................................................................................. 65
19.2.2. Effect of voids and cement content on pump-ability ................................................................... 66
19.2.3. Effects of concrete mix design ...................................................................................................... 66
19.2.4. Effect of aggregate on pump-ability ............................................................................................. 66
19.2.5. Effect of W/C ratio on pump-ability .............................................................................................. 66
19.2.6. Admixtures for pump-able concrete ............................................................................................. 67
19.3. Effect of extreme weather conditions .............................................................................................. 67
19.4. Yield stress and viscosity ................................................................................................................... 67
19.4.1. Factors influencing concrete yield stress and plastic viscosity ..................................................... 67
19.5. Self-Compacting Concrete (SCC) ....................................................................................................... 68
19.5.1. Required properties of SCC ........................................................................................................... 68
19.5.2. SCC typical tests ............................................................................................................................ 68
19.6. Shotcrete ........................................................................................................................................... 69
19.6.1. Applications of shotcrete .............................................................................................................. 69
19.6.2. Dry-mix shotcrete .......................................................................................................................... 69
19.6.3. Wet-mix shotcrete ........................................................................................................................ 69
20. Distribution of Lateral Loads to LLRSS ...................................................................................................... 69
20.1. Distribution of lateral loads to individual elements for 2-D analysis ................................................ 69
20.1.1. Assumptions .................................................................................................................................. 70
20.1.2. Procedure ...................................................................................................................................... 70
20.2. Lateral load distribution example ..................................................................................................... 70
20.2.1. X-Force .......................................................................................................................................... 71
21. Coupled Core Systems and Outrigger Systems ......................................................................................... 71
21.1. Mechanism for Coupling Actions ...................................................................................................... 72
21.1.1. Coupling action ............................................................................................................................. 72
21.2. Theoretical solutions ......................................................................................................................... 72
21.2.1. Wide beam analogy ...................................................................................................................... 72
21.2.2. Continuous medium method ........................................................................................................ 72
21.3. Coupling System Conclusions ............................................................................................................ 73
21.4. Outrigger Systems ............................................................................................................................. 74
21.4.1. Summary of outrigger systems ..................................................................................................... 74
21.4.2. Theoretical treatment of outriggers ............................................................................................. 74
22. Methods for Theoretical Treatment of Beam-Column Frames ................................................................ 75
22.1. Approximate Solutions ...................................................................................................................... 75
22.1.1. Portal method ............................................................................................................................... 75
22.1.2. Cantilever method ........................................................................................................................ 76
22.2. Additional Considerations ................................................................................................................. 76
22.2.1. Lateral stiffness of frame .............................................................................................................. 76
22.2.2. Axial deformation of columns ....................................................................................................... 77
22.2.3. Deformation due to shear ............................................................................................................. 77
23. Façade Engineering ................................................................................................................................... 78
23.1. Introduction to facades ..................................................................................................................... 78
23.1.1. Function of façade......................................................................................................................... 78
23.1.2. Condensation issues ...................................................................................................................... 78
23.1.3. Corrosion issues ............................................................................................................................ 78
23.2. Façade systems ................................................................................................................................. 78
23.3. Design considerations and loads on façades .................................................................................... 79
23.3.1. Self-weight of façade .................................................................................................................... 80
23.3.2. Wind and earthquake loads .......................................................................................................... 80
23.3.3. Structural integrity ........................................................................................................................ 80
23.4. Superstructure/façade interaction ................................................................................................... 80
23.4.1. Movements and deflections ......................................................................................................... 80
24. Basic Introduction to Fire Dynamics ......................................................................................................... 81
24.1. Introduction to Fire Dynamics .......................................................................................................... 81
24.1.1. Heat transfer ................................................................................................................................. 81
24.1.2. Heat Transfer – transient state ..................................................................................................... 82
24.1.3. Combustion ................................................................................................................................... 82
24.2. Fire Curves ......................................................................................................................................... 83
24.2.1. Severity of a fire ............................................................................................................................ 83
24.3. Façades and fire ................................................................................................................................ 83
24.3.1. compliance and performance requirements ................................................................................ 84
24.3.2. Consideration of façade fires ........................................................................................................ 84
24.3.3. Combustibility ............................................................................................................................... 84
24.3.4. Fire resistance level ....................................................................................................................... 84
24.3.5. Full-scale façade fire test .............................................................................................................. 85
24.3.6. Fire propagation on buildings ....................................................................................................... 85
25. Construction Techniques for High Rise – Burohappold Engineering ........................................................ 86
25.1. Cost Breakdown of Tall Buildings ...................................................................................................... 86
25.1.1. Construction optimisation ............................................................................................................ 86
25.1.2. Design for construction speed ...................................................................................................... 86
25.2. Core Construction ............................................................................................................................. 86
25.2.1. Efficiency of Core Construction ..................................................................................................... 86
25.2.2. Steel vs. concrete cores................................................................................................................. 87
25.3. Floor Construction............................................................................................................................. 87
25.3.1. Precast floors................................................................................................................................. 87
25.3.2. Composite floors ........................................................................................................................... 87
25.4. Column Construction ........................................................................................................................ 87
25.4.1. Composite columns ....................................................................................................................... 87
25.5. Key factors of structural systems ...................................................................................................... 87
26. Digital Engineering .................................................................................................................................... 87
27. P-Delta Effects and Axial Shortening ......................................................................................................... 88
27.1. Axial shortening ................................................................................................................................ 88
27.1.1. Dealing with axial shortening ........................................................................................................ 88
27.1.2. Differential shortening .................................................................................................................. 88
27.1.3. Calculating elastic shortening ....................................................................................................... 89
27.1.4. Minimising the effects of differential movements ....................................................................... 89
27.1.5. Corrections to shortening ............................................................................................................. 89
28. Prefabricated Modular Construction ........................................................................................................ 89
28.1. Advantages ........................................................................................................................................ 89
28.2. Design considerations ....................................................................................................................... 89
29. Design of a High-Rise Building (Case Study) .............................................................................................. 90
29.1. Stages of Project ............................................................................................................................... 90
29.1.1. Initial stages .................................................................................................................................. 91
29.1.2. Schematic Design .......................................................................................................................... 93
29.1.3. Conceptual design ......................................................................................................................... 95
1. Introduction to High Rise Building Design
1.1. Introduction There is a trend towards high-rise construction and structures that are more slender, flexible and light-weight
1.2. Definition of tall buildings A building is considered tall when its strengths and behaviour is governed by lateral loads (wind and/or earthquake). strength of individual components usually governs for low-rise buildings but lateral loads increasingly dominate the structural form with increasing height structural analysis moves from the field of statics into the field of dynamics (consideration of damping, mass and stiffness as a function of height)
1.3. Structural Design Criteria Tall building design is the significance of all three criteria
1. Strength 2. Serviceability 3. Stability
1.4. Features of High Rise Design
Effects of lateral loads due to wind and earthquakes Asses the magnitude of design lateral loads Lateral displacement of the building Accelerations Effect of movement on non-structural elements Second order effects (p-delta effects, creep, differential movements) stability against overturning and sliding Importance of members governed by net tension Importance of correct assessment of soil-structural interaction
1.4.1. Loading Accurate assessment of design loads (LL & DL, pre-stressing, foundation settlement, creep, shrinkage) is essential as conservative estimates is not affordable in high-rise design.
1.4.2. Key Issues Key issues of high-rise design include:
Floor-to-floor height Size and layout of core
1.4.3. Core optimisation The size and location of the core is governed by architectural requirements and optimising it requires consideration of:
Minimisation of material cost: often required to optimise between concrete quality, reinforcement and concrete strength
Minimisation of core area: core area is not included in net rentable area, if capitalise the lost rent from a large core area, value can be very high
Optimising core geometry: for structural performance (e.g. thicker wall at highly stressed locations) Construction time: Maintaining simplicity for quicker construction, delays add to the completion time
and costs can affect the profitability of the project
1.4.4. Floor System Fundamental aim is to minimise the floor cycle time, a more expensive floor system with quicker construction may be more profitable
Optimisation can be achieved by:
Material saving Buildability Minimising floor-to-floor height: often fixed by regulatory requirements Integrated approach to floor system design
1.5. Designing for Full Life Design Design lives tend to be 50 to 100 years and changes to buildings are often required due to lifestyle changes flexibility is encouraged as the refurbishment of buildings is becoming increasingly common
Structure: materials that have flexibility (composite steel floor with prestressed floors) Loads: design floor loadings may terminate a building’s use Access Floors: provisions for access floors Façade: design life of a façade is typically 10-20 years Vertical Elements: contingencies in loading for vertical elements and foundations Durability: important for residential buildings
1.5.1. Life-cycle costing Life-cycle costing involves costing the chosen options over the whole of its life whereas many designers base costs of options based on the initial costs. Disadvantages of Initial Cost Comparison
Ignores the operating and/or maintenance costs Assumes all components have the same design life
1.5.2. Importance of buildability and construction speed Cost of construction relates to time as well as the cost of materials as large capital funds are often tied up for a relatively long construction period
1.6. Functional Requirements Building functional requirements must satisfy:
Requirements of Site: constraints in site geometry, location, geomechanical considerations, topography, climate and seismic activity
Requirements of building program: planning and occupancy, funding, construction issues Requirements of appearance: aspirations of building owner, community, users and designer
1.6.1. Factors for a successful building
1. Friendly inviting image, that have positive values to the owner, users and observers 2. Fit the site, appropriate layout 3. Energy efficient and controllable climate 4. Allow for flexibility in layout and usage 5. Maximises layout 6. Compliments the city and its people in terms of culture 7. Cost-effective
1.7. Basic Elements A tall building consists of these basic elements
1. Vertical stack of functional areas: floor system 2. Vertical service risers: series of vertical shafts (water, wastewater, electrical, mechanical, hydraulic
services, lifts, stairs) 3. Outside enclosure (façade): protects occupants from external climatic conditions and maintains
internal conditions
1.8. Basic Planning Considerations
Lease span: distance from core to façade, depends on function, important consideration for interior planning - Typically 10 and 14m for office - Typically 6 to 9 for hotels and residential
Floor-to-floor Ceiling height: can range between 2.7-3.7m (2.7 minimum for office and as low as 2.4m for
hotels/residential) Depth of structural floor system: depends on floor load requirements, column spacing, deflections,
fire ratings Elevators: typically need one elevator per 4600 square metres of lettable area Core planning: major elements are elevator shaft, mechanical shafts, stairs and elevator lobbies Parking: proper parking facilities need to be included
1.8.1. Mechanical and electrical systems
Heating, ventilation, air-conditioning system (HVAC), water systems, wastewater systems, fire protection
High voltage systems (power for equipment, lighting and appliances) Low voltage systems (telephone system, public address systems)
2. Introduction to FEM Analysis FEM analysis is usually employed for analysis that can’t be completed through simple/traditional methods. FEM breaks the model up into smaller elements and joins elements together at their nodes. Stresses, deformations and strains are analysed for each finite element. Basic components of the model build-up include:
Geometry (nodal point coordinates) Elements connecting the nodal
points Mass properties Boundary conditions or restraints Loading (static or dynamic) Analysis options Select mesh type Determine boundary conditions and
load paths Consider independent load cases
and combinations Run/debug model Validate model
2.1. Finite element discretisation
Aspect ratios: bad aspect ratios for elements should be avoided Interfaces: Elements must not costs interfaces
2.2. Element Geometry Preferences
2D: quadrilaterals over triangles 3D: bricks over wedges, wedges over tetrahedral
2.3. Symmetry and Anti-Symmetry conditions If a line of symmetry is found, the FE analysis can be run on one-half of the problem. axis of symmetry represented by rollers
Geometrically symmetric
Material properties the same
Loads are symmetric
Same boundary conditions
