cocnrete and masonry for april 3 Flashcards
Failure to protect employees from impalement. Rebar not capped or covered.
(1926.701 (b))
Failure to establish limited access zone (LAZ) to limit the number worker in the danger zone where a masonry wall is under construction.
(1926.706(a)(1))
Failure to brace unsupported section of masonry wall over eight 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))
What are some effective control measures that can be used to guard rebar so employees cannot fall into or onto the rebar and become impaled?
- Prevent employees from working in an area where they may fall into or onto unprotected rebar.
- If this is not possible, use guardrails or other fall protection measures as outlined in Subpart M to eliminate the fall hazard from elevations.
- Rebar can be capped with special protective rebar covers to keep employees from being impaled. Do not use plastic or paper cups or tape as a rebar cover because they do not protect workers from impalement.
- The rebar can be bent (but only when an engineer has approved this practice) or the rebar can be covered with lumber (e.g., a 2” x 4” board).
What precautions must be taken for post-tensioning work?
- Access should be limited to behind the jack for those who are performing work.
- Signs and barricades are required to limit access
When placing a conrete bucket by a crane what are the two safety rules that must be followed?
- 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 over head buckets.
Concrete mixers with capacity greater than ___ must have mechanical device to clear skip of ___.
1 cu. yd.
2. skip of materials
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 the wheels on either side.
A 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____.
dead man switch
Bull float handles must be ____ if electrical contact is possible.
non-conductive
What are some of the effective control measures that can be used to eliminate the hazard of being in the danger zone to protect employees from being struck by flying brick and block in the event of a wall collapse?
- Until the wall has gained sufficient strength that overturning (collapse) is no longer a hazard, keep employees out of the area where the wall is being constructed unless they are actually engaged in constructing the wall.
- The most effective control measure is to follow the standard by marking off an area with tape, rope, or chain or any other material that will indicate to employees that they are not to enter the zone (area) that has been marked.
- The zone should be equal to the length of the wall under construction and extend out a distance equal to the height of the wall to be constructed plus 4 feet. So if the wall to be constructed is 10 feet high and 30 feet long, the zone should be 14 feet x 30 feet.
What are some of the ways to brace a wall over 8 feet to provide protection against the hazard of collapse?
a. The project engineer or competent person should determine how best to brace the wall. According to the Magazine of Masonry Construction (November 1988) a typical masonry wall brace includes a vertical member, an inclined strut, stakes, and if necessary a strut-brace.
b. Scaffold planks (2 x 10s) are typically used as the vertical member and the inclined strut, and 2 x 4s for stakes and strut-brace. 2 x 4s and 2 x 6s are considered by most experts to be inadequate for vertical members or inclined struts. All lumber must be in serviceable condition.
c. The American National Standards Institute’s Standard for Concrete and Masonry Work, ANSI A10.9-1983 standard recommends that “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.”
____ must be secured with wire rope or equivalent.
Tremies
______ required for work on equipment used for concrete & masonry.
lockout/tagout
whenn dealing with cast-in-place concrete, formwork on must be designed, fabricated, erected, supported, braced and maintained so that it will be ____.
capable of supporting without failure on all vertacle and lateral loads.
When dealing with cast in place concrete drawings or plans and any revisions for jack layout, formwork, etc. _____.
must be available on the jobsite.
Drawings and plans dealing with cast-in-place concrete must have what?
- Formwork scaffolding
2. shoring equipment
April, ___ __ workers killed in the collapse of scaffolding used to pour concrete for a cooling tower under construction. __ workers fell more than __ feet and __ were crushed to death on the ground.
1978, 51, 45, 150 feet, 6
____ to be inspected prior to erection, before , after, & during, concrete placement
shoring and re-shoring
when dealing with cast in place concrete _____ is not to be used.
damaged shoring
When dealing with cas in place concrete Shoring that is found to be _____.
damaged shall be reinforced
The sills for shoring must be…..
sound, rigid, and capable of carry the maximum intended load
All ______, ______, ______, and ______ must be in firm contact with the foundation and the form – and secured when necessary.
base plates, shore heads, extension devices, and adjustment screws
______ on shore heads are not allowed unless designed for this (Means loads not centered on head, lateral loads can cause failure).
Eccentric loads
Whenever single post shores are tiered additional requirements to be followed are that the shores must be:
- Designed and inspected by qualified person 2.Vertically aligned
- Spliced to prevent misalignment
- Braced in two directions at splice level and at each tie
are not to be removed until concrete strength is sufficient to support its weight & any other imposed loads
shoring and re-shoring
Adjustment of single post shoring not to be made after __________.
Placement of concrete
_______ to be erected as original shoring is removed as needed for support.
Re-shoring
What two things should be done when stripping formwork?
Use spotter and restricted access area.
Cast-in-Place Concrete Slip Forms 3 rules to go by.
- 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 2 main rules.
- Rolls of reinforcing wire shall be anchored to prevent recoiling.
- Reinforcing steel for walls, columns, etc. adequately supported to prevent overturning.
Contacting _____ from concrete exposure can cause severe burns to skin & eyes.
dermatitis
What is the best practice for concrete safety?
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. Washing facilities and eyewash solution should be provided.
This technique prevent silica exposure.
Wet sawing
Tilt up inserts must have __ safety factor
2/1
Precast inserts must have __ safety factor
4/1
All lifting hardware must have ___ safety factor
5/1
When erecting precast wall units what practices must you follow?
- Precast wall units, structural framing & tiltup wall panels must be supported (braced) to prevent overturning.
- No employees permitted under precast members being lifted or tilted except only those required for erection.
Lift slab construction operations.
- Must be planned by a Professional Engineer.
- Only essential employees allowed in work area.
- Jacks must be marked with rated capacity.
- Jacks to have 2.5/1 safety factor.
- Jacks to have safety device in case of failure.
- Lifting operations to be supervised by a competent person.
- Slab must be kept level within 1/2” during lift operations.
- Welding to be done by certified welder.
April, 1987 Lift slab construction project in Bridgeport, Connecticut __ workers killed, __ injured when two adjoining towers collapsed at the 6th & 9th levels of construction Multiple failures in design system and construction practices
28, 12
Masonry Construction Limited Access Zone 5 rules to go by.
- Established prior to start of work for all walls over 8 feet.
- Walls 8 feet and less, do not have to establish zone if adequately braced.
- Equal to the height of wall + 4’ & run full length of wall.
- Establish on non-scaffolded side of wall.
- Access restricted to only those employees constructing wall.
According to the Council of masonry wall bracing how do you adequately brace a wall?
A restricted zone shall exist on both sides of a masonry wall until the wall obtains final lateral stability from supporting structural elements.
limited to maximum of one working day, during which the masonry is laid above its base or highest line of bracing and, at the end of which, required bracing is installed.
Initial period
time following initial period until wall is connected to structural elements
Intermediate period
Restricted zone to be evacuated during initial period when wind speeds exceed ___.
20 mph
Restricted zone to be evacuated during the intermediate period when wind speeds exceed __.
35 mph
To determine maximum un-braced height of walls above grade or highest line of lateral support _____.
see table in standard-council of masonry wall bracing
ANSI A10.9-1983 recommends that “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 _____. Braces or shores shall be secured in position.”
bracing design
The ______ or competent person should determine how best to brace the wall.
project engineer
A typical masonry wall brace includes:
- vertical member
- inclined strut
- stakes
- strut-brace
2 x 4s and 2 x 6s are considered by most experts to be ______.
inadequate for vertical members or inclined struts
Flying deck forms 6 best practices
- Qualified person to inspect form prior to movement.
- No one other than rigger on top of form after roll out.
- 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
