week 10

• Tilt-up panel


  An essentially flat concrete panel; cast in a horizontal position, usually on-site; initially lifted by rotation about one edge until in a vertical or near-vertical position; transported and lifted into position if necessary; and then stabilized by bracing members until incorporated into the final structure
• Tilt-up construction system process


  1. Suitable casting bed

  2. Simple edge formwork and basic reinforcement

  3. Suitable cranes and lifting inserts

  4. Fixings

  5. Concrete placement at or near ground level

  6. Traditional finishing techniques for slab on ground construction

  
• Tilt-up construction system process cont'd

  1. Panels cast one on top of the other (stack cast)

  2. Crane lifts and moves panels into position

  3. Panels temporarily braced until connections made

  4. All operations usually completed from ground level
• Tilt-up construction


  • Panel size can be varied, with the maximum size being limited by the capacity of the lifting equipment or transport limitations
  • Economic benefits not at the expense of quality, durability, performance or appearance
  • Thorough planning but results in very quick erection of solid walled buildings, using readily available materials, tradesmen and equipment
• Australian Standard AS 3850-2003 Tilt-up Concrete Construction

  • Sets out requirements for planning, design, casting, transportation and erection of tilt-up panels
  • Must be complied with by employers/contractors undertaking concrete tilt up work
  • Does not apply to other precast concrete members not rotated about one edge and/or temporarily braced
• Sections of AS 3850-2003 that must be complied with

  • Design and drawings
  • Materials, components and equipment used in manufacturing
  • Manufacturing
  • Transport, cranage, temporary storage and erection
  • Design, construction and removal of temporary bracing and fixing
• Typical connection details


  • Panel to slab connection
  • Bracing connection to slab or deadman
  • Panel to panel connection
• Panel seating detail


  Panels sit on neoprene shims to ensure even loading and allow levelling
• Design considerations for tilt-up construction

  • Building should be designed specifically for this form of construction
  • Maximise standardisation of panel design, including reinforcement, fixings and inserts
  • Optimise panel size by balancing maximum lifting capacity and benefits of speed and mobility on site
• Planning considerations for tilt-up construction

  • Consultation of design/construction team and lifting contractor to develop construction and erection sequence
  • Decide whether to cast panels inside or outside the building
  • Plan casting layout and brace-fixing positions to facilitate speedy erection and limit crane set-ups or double handling
  • Build-in flexibility to accommodate unforeseen changes during construction
• Precast concrete panel construction


  Concrete slab cast in a factory or casting facility, transported to site, and then placed into final position by crane

  
• Precast construction is distinct from and often confused with tilt-up construction, the key difference being that precast panels are manufactured off site
• Precast panels


  • Precision product with superior finish
  • Suitable for projects requiring exceptionally high standard of finish to wall surfaces
• Benefits of precast panel construction

  • Used as building envelopes for office, retail, schools, residential and public buildings
  • Used where there is insufficient room or access onsite for casting panels, exceptionally high finish is required, or casting unable to be achieved onsite
  • Lends itself to smaller panels or more irregular sizes and shapes than tilt-up
  • Coloured concrete and cast in textures can enhance external appearance
• Why precast panel construction

  • Panels can be manufactured off site ahead of time, avoiding on-site casting
  • Can be erected without a floor slab, allowing for superior quality post construction slab
  • Inherent fire rating characteristic similar to tilt-up panels
• Precast panel types for building envelopes

  • Cladding
  • Load-bearing wall units
  • Shear walls
• Precast cladding


  Most commonly used precast concrete components for building envelopes, do not transfer vertical loads but enclose the space
• Precast load-bearing wall units

  Resist and transfer loads from other elements, cannot be removed without affecting building strength or stability
• Precast concrete shear wall panels

  Provide a lateral load resisting system when combined with diaphragm action of floor construction, effectiveness dependent on panel-to-panel connections

  
• Precast panel types of connections

  • Bolted connections
  • Welded connections
• Load-bearing wall units


  • Resist and transfer loads from other elements
  • Cannot be removed without affecting the strength or stability of the building
• Precast concrete shear wall panels

  • Provide a lateral load resisting system when combined with the diaphragm action of the floor construction
  • Effectiveness is largely dependent on the panel-to-panel connections

  
• Bolted connections


  • Simplify and speed-up the erection operation
  • Final alignment and adjustment can be made later without tying up crane time
• Welded connections


  • Made by embedding a steel in the precast concrete panel and welded to the structural steel member
• Dowel/Anchor Bolt Connections


  • Threaded anchor bolts and/or rebar anchor dowels protrude from the foundation and are connected to the precast panels
• Buildability


  • There should be a conscious striving for 'buildability'
  • Factors to be considered include: position of lifting operator, workspace available, realistic tolerances, fixing and joint details
• Safety considerations for tilt-up and precast panel construction

  • Panel design
  • Cast-in lifting and bracing inserts
  • Concrete strength and curing time
  • Drawings
  • Braces
  • Wind loading
  • Deadman design
  • Post installed anchors
  • Engineer certification
  • Delivery and unloading
  • Cranage (capacity, ground condition, lifting gear)
  • Erection of panels
  • Operation of plant near braces and panels
  • Working at height
  • Proximity to overhead powerlines
  • Licensing
• The Tilt-up and Precast Panel Construction Code of Practice 2003 (worksafe.qld.gov.au) provides key safety considerations