Panel
How should a panel that cannot be set in its final position after being lifted be handled?
Must place it as close to final location and temporarily brace it. Must NOT set it down horizontally.
How can you test the effectiveness of a bond breaker after it is in place?
Dropping water on the slab and seeing if it beads up. If it does, the bond breaker is still effective.
What is a "blind" pick?
When the crane operator loses sight of the rigging after panel has been lifted
How many panels can an average two-man crew complete the formwork for (ready for reinforcement) in a day?
8-12 a day
Define a closure strip.
A strip of the slab on grade along the exterior that is not poured until the panels have been placed.
When should the required lateral bracing and knee bracing be installed?
As soon as the crane and crew are clear, and before the next panel is erected if possible.
What is the recommended safety factor for brace anchors?
1.5
List acceptable methods for curing tilt-up panels.
1. Spraying the panel surface with a curing compound per the manufacturer's guidelines
2. Wet cure
What should be done to free a panel that sticks to the floor slab?
Carefully use wedges and pry bars to help release the panel
What is the preferred time to attach braces to the panel when casting inside face up?
Before lifting the panel
Who gives the crane operator the signals during the panel lift?
Rigging foreman
What is the minimum compressive strength and minimum flexural strength required for panels prior to lifting?
Min. compressive strength: 2500 psi
Min. flexural strength: 400-500 psi
How should bond breaker be placed when reinforcement is already in place?
Reinforcement must be removed before bond breaker is sprayed. Rebar CANNOT come into contact with bond breaker.
How many inches should a panel be within plumb prior to releasing the rigging?
4 inches
What distance does OSHA require as a minimum horizontal separation between power lines and crane rigging?
20 feet
Panel layout and sequence
What is the primary reason water is removed from the panel perimeter and openings prior to lifting?
Standing water prevents air from entering under the panel and creates additional load required to break the bond.
How are intersecting braces handled at corners of buildings?
Braces may have to be skewed or have their heights staggered
How does the addition of water to fresh (green) concrete affect the concrete's strength?
It lowers the compressive strength (f'c)