Steel and Concrete framing

Steel
1. Advantages
  1. Quick erection
  2. Fewer site activities
  3. Little risk of site error
  4. Can be made to fine tolerances
  5. Light: 60-70% lighter than concrete frame
  6. Cold weather has little effect on site progress
  7. Adaptable in future
  8. High risidual value
2. Disadvantages
  1. Changes to design after production can be expensive
  2. Usually require bracing to prevent racking (deformation) in high winds
  3. Mistake from manufacturer can be detromental as each frame is usually unique
  4. Can buckle in fire (fire protection required)
3. Basic elements
  1. Connections
  2. Composite construction
  3. Cold formed steel sections
  4. Welded construction
  5. Shapes
    1. Universal beams
    2. Tubes
    3. Channels
    4. Angles
  6. Standard and non standard sections
  7. Beams
  8. Built up sections (cantilevered beams)
  9. Bracing
  10. Girders and trusses
  11. Hot rolled mild steel sections
  12. Colunms and stanchions
  13. Frame layout
4. Frame layout
  1. Regular/ closely spaced grid
  2. Deeper, lighter sections are more effective
  3. Simplest form is universal beams and stanchions
5. Girders/ Trusses
  1. Deep trusses (often full storey height)
  2. Space trusses (applied to roofs)
  3. Plate girders (15/36m spans)
  4. Greater spans/ Heavier loads
6. Collumns and stanchions
  1. Universal sections from Corus
  2. Design of splice is key factor
  3. Universal/ Compound sections
  4. Circular/ Rectangular
  5. Lattice or braced
7. Connections
  1. Stanchion bases (act as cantilever)
  2. Stanchion splices 10-12m lengths)
  3. Beam to beam( splice plates/ weak point/ Headroom)
  4. Beams to stanchions ( Beam resting on beam/ web to web)
  5. Welded or bolted
8. Cold formed sections
  1. Pressed steel (formed into shape by press breaking or bending)( Flooring/ Roofing elements)
  2. Cold rolled sections (longer elements) (Variety of shapes and sizes)
9. Bracing
  1. Lateral resistance to wind
  2. Rigid frames (stiff connections/ plate or gusset stiffeners)
  3. Shear walls (lift shafts/ Stairwells/ Stiff verticle elements)
  4. Diagonal (Kor X) Bracing- Principle of triangulations/ Rigid diaphragm
10. Composite construction
  1. Concrete floor slabs( in-situ or precast)
  2. Concrete encasement (stiffening action)
  3. Metal floor deck (stud welding)
  4. Interaction of structural members
11. Beams
  1. Connection is key
  2. Normally universal sections from Corus
  3. Heavier loads need to develop stiffer beams (girders)
12. Welded construction
  1. Lighter than bolts (20-25% lighter)
  2. Bolt holes eliminated
  3. Simpler connections
  4. Rigid end connections
Concrete
1. Costs
  1. Frame
    1. Difference between concrete and steel insignificant
  2. Foundation
    1. 3% of whole project
    2. More expensive the heavier the reinforced concrete
  3. Cladding
    1. Thinner= cheaper
    2. Represents 25% construction costs
  4. Partitions sealing
    1. Flat soffits simplest
    2. 4% of frame cost
  5. Air tightness
    1. Part L of building regs require pressure tests
    2. Failure= time consumption
  6. Services co-ordination
    1. Reduces risk of errors
    2. Permits maxiumum offsite fabrication, high quality work and quick instilation
    3. Should reduce costs
    4. 15% added on for horizontal services
    5. Soffit provides zone for services distributor
  7. Fire protection
    1. Not requied
  8. Acoustics
    1. Part E building regs= Finishings to the walls, concrete minimises requirement
  9. Whole life value
    1. Range of inherant benifits
      1. Fabric energy storage
      2. Fire resistance
      3. Sound
      4. Low operational costs
      5. Little maintenance requirements
  10. Whole life value
    1. Lower operational costs
    2. Low maintenance costs
  11. Programme
    1. Floor to floor construction periods reduced
    2. Service instalation/ Follow on trades can commence earlier on in the project
  12. Vibration
    1. Small due to concrete
2. Concrete frame- Material cost breakdown
  1. Cost breakdown
    1. Concrete 40%
    2. Shuttering 32%
    3. Reinforcement 28%
  2. Overal
    1. 60% material
    2. 40% labour
3. Precast
  1. Important to mix precast and non-precast
  2. Can meet most challenging design requirements
  3. Works well with non-precast elements
  4. Efficient structures provide a sustainable building
  5. Can be encourperated into any shaped building
  6. Research for a more sustainable strategy;
    1. Energy
    2. Supply chain
    3. Employment
    4. Resources
    5. Waste
    6. Social/ Community
    7. Health and safety
4. In-situ
  1. Positives
    1. Reduced defliection in members
    2. Uniform distribution of bending moments
    3. Design flexibility
    4. Less wasted material
  2. Negatives
    1. Different foundation settlements
    2. Temperature movement (expansion joint)
    3. Future demolition
5. Formwork systems
  1. Jump Form
  2. Vertical panal system
    1. Crane lifted panal system
    2. Reusable
  3. Tunnel form
    1. Form repetitive cellular structures
    2. Enables construction of horizontal and vertical elements together
    3. Productive
    4. Good for
      1. Hotels
      2. Low/ high rise housing
      3. Hostels
      4. Prisons
  4. Falsework
  5. Table form/ flying form
    1. Mobility
    2. Quick instalation
    3. Good for regular planned buildings
  6. System collunm formwork
    1. steel
    2. aluminium
    3. Cardboard
  7. Shuttering
    1. Temporary
    2. Contains poured concrete until it can support itself
  8. Horizontal panel system
    1. Small/ lightweight
    2. Versatile
    3. Aluminium/
    4. Tensile steel
    5. Fibre glass
    6. Special plastic
  9. Slip form
    1. Formwork raised in vertical continuos process
    2. Self supporting
    3. Extruding a reinforced concrete section
    4. Sections rise continuously ( about 300mm per hour)
    5. Form any regular shape or core
    6. Three platforms to formwork
6. Choice of structure
  1. Flat slabs
    1. Versatile
    2. minimum depth
    3. Fast construction
    4. Flexible colunm grids
  2. Ribbed and waffle slabs
    1. Light
    2. Stiff
    3. Good with slab vibration
  3. Beams and slabs
    1. Irregular grids
    2. Wide and flat or narrow and deep
  4. Post tensioned slabs
    1. Flat
    2. Thinnest slab type with long spans
  5. Tunnel form
    1. Cellular structures

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Steel and Concrete framing

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