G8 - Specialized Concrete Formwork - Tilt-up construction Flashcards
Explain tilt up-construction
1) Panel cast on slab, cured to design strength
2) Tilted up and braced
3) Crane next
4) Lace the braces and weld the panel connection
Why is the floor slab required to be very strong?
To support the weight of 1) Crane 2) Panels
Why should the floor slab be very flat?
Smoother wall finish
List four types of buildings that are built using tilt-up construction:
Warehouse, office, institutional and residential.
Where is “infill” concrete placed?`
At the base of a wall.
Describe the formwork that is used for tilt-up wall panels.
Wood or metal forms.
How are newly erected tilt-up panels usually held in position?
Metal bracing
What is the purpose of the grout pads?
Leveling panels
Describe how the base of the tilt-up wall panels is held in place:
Infill concrete and dowels.
List two differences between a normal floor slab and a floor slab for a tilt-up building:
Tilt-up is level, smoother, and stronger.
Which surface of the finished wall will have the lifting inserts exposed?
Inside
What is a rebound hammer?
Engineer tool for concrete strength.
Describe what is covered in the pre-lift safety meeting.
The responsibility of each person, where to not stand, signal person, and rigging safety checklist.
Describe the lifting of a wall panel:
1) Check wind
2) Clear workers
3) Outriggers extended and blocked
When are pilasters used to join wall panels?
To support concentrated loads.
What holds the wall panels permanently in place at the top of the wall panel?
Welded or bolted to steel ledger.
What are the wall braces connected to on the wall panels?
Inserts .
Temporary bracing for tilt-up construction must not be removed until:
Inspected by a building design engineer he/she has written a statement that the bracing is no longer needed.
Tilt-up panels must reach what strength before lifting?
Required strength specified by the engineer.
Crane must hold panel until:
Steel braces are bolted into place.
Once braces are installed on tilt-up panels, then:
Crane can release the panel and pick up another.
Panels are bolted together with:
A steel angle iron is also used as a ledger to support the roof trusses.
Footings for a tilt-up panel:
Cast on undisturbed soil at an elevation that will put the bottom of the tilt-up wall panel below the elevation of the floor slab by at least 12”
Rebar is cast in an L shape into the bottom of the wall panel for what purpose:
To connect the infill concrete to the wall panel
What are grout pads set for on each footing?
To allow the elevation to be exactly controlled.
After the panels are in their final location: The footing is covered with?
A mound of fresh concrete to keep the panels from moving during the backfilling of the infill area.
The floor slab is kept back from the perimeter of the building by approximately 4-6 feet:
This allows working room around the footings supporting the tilt-up wall panels.
How best to stack panels?
To reduce movement of crane, stack panels
Panels with openings should be at the top or openings are filled with formply, to support the next panel.
What is usually required around lifting inserts?
Extra re-bar
Bracing inserts must be located where?
Find them in the brace inserts as seen in panel shop drawings.
How is concrete placed in tilt-up construction?
Accelerator is used in the mix to speed the strength gain and allow lifting of the panels to begin soon after placing concrete.
Which side of the tilt-up panel is the finished side?
The bottom side (slab must be clean and free from oil and other debris.
Inside of building in tilt up panel is covered with:
Insulation and wall finish.
Site engineer uses what test to determine the concrete strength?
Will use a rebound hammer to determine the actual strength of the concrete for each panel.
Amount that the hammer rebounds indicates the strength, stronger the concrete, the more it rebounds.
How are wall braces installed in tilt-up construction?
Extend from the supporting slab to near the top, secured with bolt. bottom plate is installed square to the wall
Supported near their midpoint by knee braces
How are braces connected together?
With cross-lacing at mid-point Attached to the braces with brackets.
Openings in tilt up panels are supported how?
Strongbacks are added to panels with openings in them to support the narrow pieces during lift process.
Most rigging systems for tilt-up involve what components?
Spreader bar is equipped with pulleys that allow the sling lengths to self-adjust as the panel is tilted up from the floor slab.
What is used to support roof trusses?
A steel ledger bolted at the top of the wall panels.
Roof construction provides what stability?
A huge diaphragm (Horizontal shear surface) that braces all of the walls together.
Top of the walls are finished with?
Cap flashing, the flashing continues into the roof deck.
Pilaster forms:
Support vertical loads of overhead beams. Pilasters are formed using pilaster clamps.
