G4 - Describe Shoring & Re-Shoring for Falsework Systems Flashcards
What is the slenderness ratio?
1:50 Typical ratio. of minimum thickness of post to unsupported height.
Describe three ways shores are made adjustable:
1) Screw Jack
2) Ellis Clamp
3) Wooden Wedges
Why are re-shores not fitted tightly to the concrete that they are supporting?
To not put undue pressure on concrete while reshoring.
Describe a slab table.
Truss shoring, stringers, joists, plywood deck & finally screw jacks.
What are fly forms?
Fly table or gang tables lifted by a crane.
How are Aluma beams attached to false work?
Slotted bottom, and bolt aluma clip & nut.
What is a mudsill for?
Distributes the weight.
What is the process that is used to cycle the formwork and re-shores for a multi-story building:
1) Form
2) Shore the pour
3) Cure
4) Strip
5) RESTORE
How should re-shores be placed when there are point loads above them?
Directly under point loads, also to support the slab.
How should re-shores be placed when there are no point loads above them?
To support slabs and beams in rows to be braced.
Two types of re-shoring systems:
Post & Scaffold.
What components does falsework require?
1) Foundation, vertical & horizontal structural components, horizontal bracing in both directions and diagonal bracing.
When is 4x4 timber used in falsework?
When elevations are varied and as re-shores to support the concrete as it cures.
4x4 wooden restores should be cut how much shorter than the intended supporting length?
1 to 1 1/2” inches short, allow for wedges to adjust to desired height
Also to avoid stressing the green concrete by pounding a tight re-shore into place.
Slenderness ratio formula:
Convert feet into inches and divide by 50
EX 18 ft post
18 x 12 = 216 INCH
216 / 50 = 4.32”
4.32 greater than the smallest dimension of post of 4”, so post needs lateral support.
How does an Ellis Clamp work?
As the force is exerted onto the top of the shore, the right-hand side of the clamp is forced down. As the right-hand side tries to move down the clamp tightens up.
Single telescope steel shore:
Often used as part of falsework. Shore head is used to accommodate a stringer and each shore braced at mid-point in both directions to resist bowing.
All parts of scaffold shoring must be from same manuf. True or False?
True
Scaffold shoring usually sits on a mudsill and is used to support:
Stringers that support the formwork
Should formwork include a form removal process that allows the formwork to be stripped safely and efficiently?
Yes, so materials can be reused.
The contractor must provide what:
1) Erection drawings
2) Supplementary instructions that clearly show all info. to accurately and safely assemble the concrete formwork, falsework, and re-shoring to the design requirements.
The re-shoring plan should show:
1) Size and spacing of re-shores
2) Required concrete strengths necessary prior to the release of the falsework support & removal of any formwork
3) Detailed schedule of how the falsework and formwork are to be removed to prevent overloading of any part of the structure or other falsework and formwork
Shoring place under recently stripped slabs concrete members, until they gain full strength, are called:
Re-shoring
The amount of deflection is part of the building design and also part of the:
Erection drawings, required by WorkSafe BC
Re-shores must not LIFT concrete but
Carry the additional live load that will be imposed on the concrete member by the formwork for the next floor of construction
Days 1-3:
Column forms setup, braced, reinforcing installed then concrete is placed.
Day 4-10:
Column form stripped
Flyform tables lifted into place
Additional slab formwork is built to complete the slab formwork between tables
Trades conduit, systems and rebar are installed,
Concrete placed and finish for second floor
Day 11-14
Second-floor column form set up, braced, reinforcing installed and the concrete is placed.
Day 15-23
Second floor column forms are stripped and column forms are set aside
Fly form tables then dropped and lifted onto 2nd floor, restores are immediately placed directly under the foot of the fly form tables
Extra re-shore is placed under the slab at mid point
Use chalk marks left on underside of the slab to position eshores
Formwork is finished and sub-trades complete work
The size, type and spacing of re-shores will be specified on the:
Erection drawings
Re-shores should be prevented from accidental dislodgement by supporting them on:
Mudsills at the bottom and lacing them together with bracing
