Official concrete and masonry study guide Flashcards
What Subpart is concrete and masonry under?
Subpart Q 1926.700 – 1926.706
Failure to protect employees from impalement – rebar not capped or covered.
(1926.701(b))
Failure to establish a limited access zone (LAZ) to limit the number of workers in the danger zone where a masonry wall is under construction.
(1926.706(a)(1))
Failure to brace unsupported section of masonry wall over 8 feet in height.
(1926.706(b))
Failure to have drawings or plans at the jobsite to indicate jack layout and formwork placement.
(1926.703(a)(2))
Mushroom Cap
Ineffective
Square Cap with Reinforced
Effective
For Post Tensioning work, the following precautions have to be followed:
- Access shall be limited behind jack to those performing the work
- Signs & barricades are required to limit access
Concrete Placing by Crane and Bucket
- Employees are not allowed to work under concrete buckets being lowered or elevated into position.
- As much as practical, buckets should be routed to minimize the number of employees exposed to overhead buckets.
Concrete mixers with capacity greater than ___ must have mechanical device to clear skip of materials.
1 cu. yd.
Guardrails should be on each side of ___.
skip
Compressed air hoses on concrete pumping systems must have _____.
fail-safe connectors
Masonry saws must have _________.
Semicircular guard enclosure
Concrete buggy handles cannot extend ______.
past wheels on either side
Concrete pump hose must have ______ to prevent separation under load.
connectors
Concrete buckets with hydraulic release must have a device to prevent ______.
accidental dumping
Power concrete trowels must have a ____.
dead man switch
Bull float handles must ______ if electrical contact is possible.
non-conductive
Tremies must be secured with _______.
wire rope or equivalent
_______ required for work on equipment used for concrete & masonry.
Lockout/tagout
When dealing with cast-in place concrete,____ must be designed, fabricated, erected, supported, braced and maintained so that it will be capable of supporting without failure all vertical and lateral loads.
Formwork
When dealing with cast-in place concrete, Drawings or plans and any revisions for_______. must be available at the jobsite.
jack layout, formwork, scaffolding, and shoring equipment
April, 1978 ___workers killed in the collapse of scaffolding used to pour concrete for a cooling tower under construction. ___ workers fell more than ___ feet and six were crushed to death on the ground.
51, 45, 150
____to be inspected prior to erection, before , after, & during, concrete placement
shoring
Damaged shoring is _____.
not to be used
Shoring that is found to be damaged must be ______.
immediately reinforced
______ must be sound, rigid, and capable of carry the maximum intended load.
sills for shoring
All base plates, shore heads, extension devices, and adjustment screws must be in _____________.
firm contact with the foundation and the form-and secured when necessary.
______ on shore heads are not allowed unless designed for this (Means loads not centered on head, lateral loads can cause failure)
Eccentric loads
Shoring & re-shoring are not to be removed
until concrete strength is sufficient to _______.
support its weight & any other imposed
loads.
Adjustment of single post shoring not to be
made after ________.
placement of concrete
Re-shoring to be erected as original shoring is ____ as needed for support.
removed
Formwork stripping is hazardous. What should be done when stripping formwork?
Use of spotter and restricted access area
Cast-in-Place Concrete
Slip Forms
- Scaffolds or work platforms required for slip
forms. - Design must be adequate.
- Safe rate of lifting must not be exceeded.
Cast-in-Place Concrete
Reinforcing Steel
- Rolls of reinforcing wire shall be anchored
to prevent recoiling. - Reinforcing steel for walls, columns, etc.
adequately supported to prevent overturning.
Contacting dermatitis from concrete exposure can cause severe burns to skin &
eyes. What is the best practice to prevent this?
- Employees should wear full-length trousers,
long-sleeve shirts, rubber boots, and gloves
and avoid prolonged contact with concrete. - Employees exposed to concrete splatter
should wear eye protection.
3.Washing facilities and eyewash solution
should be provided.
What two things can be done to prevent silica exposure?
- NIOSH approved mask
2. Wet sawing
Precast Concrete three ratios
a. Tilt up inserts must have 2/1 safety factor
b. Precast inserts must have 4/1 safety factor
c. All lifting hardware must have 5/1 safety
factor
April, 1987
Lift slab construction project in Bridgeport,
Connecticut
28 workers killed, 12 injured when two adjoining
towers collapsed at the 6th & 9th levels of
construction
Multiple failures in design system and
construction practices
L’Ambiance Plaza
Walls over ___ in height, must be “adequately”
braced – OSHA
8 feet
When bracing masonry walls A _____ shall exist on both sides of a masonry wall until the wall obtains final lateral stability from supporting structural elements.
restricted zone
When bracing masonry walls - time following initial period until wall is connected to structural elements.
Intermediate period
When bracing masonry walls - Restricted zone to be evacuated during initial period when wind speeds exceed….
20 mph
When bracing masonry walls - Restricted zone to be evacuated during the intermediate period when wind speeds exceed…..
35 mph
The ___________
should determine how best to brace the wall.
project engineer or competent person
A typical masonry wall brace includes:
- vertical member
- inclined strut
- stakes
- strut brace
Scaffold planks (2 x 10s) are typically used as the…….
vertical member and the inclined strut
What are typically used for for stakes and strut-brace?
2 x 4s
Prevention of ____ of critical importance
in high rise construction.
falling debris
When hooking up flying forms what is necessary?
fall protection
What are the most frequently cited violations?
- Failure to protect employees from impalement.
- Failure to establish Limited Access zone.
- Failure to brace unsupported section of masonry wall over 8 feet high.
- Failure to have drawings or plans or jack layout and formwork placement.
How can rebar be guarded to avoid impalement?
- Prevent employees from working in an area where they may fall into or onto unprotected rebar.
- If this is not possible use PPE or guardrails.
- Rebar can be capped with protective covers.
- The rebar can be bent when engineer says ok, or it can be covered with 2x4s.
What should be done to avoid being in the danger zone, when masonry walls are being constructed?
- Only employees involved in building the wall should be in the danger zone, until it has gained sufficient strength.
- Mark off area with tape or chains.
- Created a limited access zone that is as wide as the wall and as long as the height of the wall plus four feet.
What should be the dimensions of a limited access zone around a masonry wall?
The width of the wall x the height of the wall plus 4.
The project engineer or competent person should determine how best to brace the wall. A typical masonry wall has a Vertical member, inclined strut, stakes, and strut brace.
Magazine of masonry construction novemeber 1988.
Scaffold planks (2x10s) are typically used as the t, and
vertical member and the inclined strut
2x4s and 2x6s are considered by most experts to be inadequate for
vertical members or inclined struts.
2x4s are typically used for
stakes and strut-brace.
The support or bracing shall be designed by or under the supervision of a qualified person to withstand a minimum of 15 pounds per square foot. Local environmental conditions (e.g. strong winds) need to be considered in determining the bracing design. Braces or shores shall be secured in position.
The American National Standards Institute’s Standard for concrete and masonry work, ANSI A10.9
Whenever single post shores are tired additional requirements to be followed are that shores must be:
- Designed and inspected by competent person.
- Vertically aligned
- Spliced to prevent misalignment
- Braced in two directions, at tier and splice level.
Lift slab concrete eight rules:
- Must be planned by professional engineer
- Only essential employees allowed in work area
- jackes must be rated with capacity
- jacks must have a 2.5/1 safety factor
- Jacks to have safety device in case of failure
- Lifting operations supervised by competent person
- slab must be with in 1/2” during lift slab operations.
- welding done by certified welder.
Flying deck forms best practice:
- Qualified person to inspect prior to movement
- No one person to inspect form prior to movement.
- Fall protection anchored to structure for rigger.
- Tag line required on form
- No one permitted on form during movement
- Safety line attached to form during roll out operation.
