Masonry Bracing Life Safety Considerations During Construction of Masonry Walls.
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Transcript of Masonry Bracing Life Safety Considerations During Construction of Masonry Walls.
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Masonry Bracing
Life Safety Considerations During Construction of
Masonry Walls
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FACTORS TO CONSIDER
Who is responsible for wall bracing?
Engineer General Contractor Masonry Contractor Qualified Person
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CODE REQUIREMENTS 1926.706(b) All masonry walls
greater than 8 feet in height must be braced to prevent overturning and collapse,
Unless adequately supported so it will not overturn or collapse
Bracing must remain in place until permanent supporting elements of the structure are in place
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Code Requirements
THEN WHAT? Code does not give
direction for spacing of braces Vertical Horizontal Additional Height
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Code Requirements
LIMITED ACCESS ZONE (L.A.Z.) 1926.706(a)
Some common misconceptions: Limited Access Zones do not take
the place of wall braces, Wall braces do not take the place
of L.A.Z, Both are required
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Test Wall Construction
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Test Wall Construction 8 in. Lightweight Block 2 - #4 Horizontal Rebar spaced
4 ft. on center #5 Vertical Rebar spaced 4 ft.
on center Coil Loop Inserts with ¾” coil
bolts 2000 psi grout at rebar
locations Grouting in pours of 8ft.
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Test Wall Construction
Coil Loop Inserts installed around a vertical rebar and placed behind a horizontal rebar as shown
Picture of coil here
Wall Brace connection
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Test Wall ConstructionWhy a coil loop insert? Past industry practice has been anchor
bolts set in grout and then attach brace Grout needed to set for 12 hour minimum Leaves window of exposure of 12 hours or
more This method allows braces to be installed
before the grout is placed in block Life safety issue 35 mile wind protection Won’t show where braces were installed
after removal
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Base Connection
Must be evaluated by a Qualified Person
Concrete block deadweight Test wall deadweight 3400 lbs
Slab connection
Anchor bolt set in concrete
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Base Connection
Slab Deadmen
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Base Connection
Wedge Anchor
Tang Bolt
Super Bolt
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Spacing of Braces:
Vertical Placement
Code requires Wall Braces above 8 ft.
No direction as to spacing
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Spacing of Braces:Recommended Horizontal Spacing: No direction from the code 20 foot spacing 10 ft from end of wall or control joints Works with 20 foot lengths of rebar Allows for scaffolding, trucks,
forklifts, and other equipment to work between braces
Creates a safe and efficient environment for workers
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Spacing of Braces:
What does all of this do?
Creates a crisscross rebar mat in the wall
Uses materials already in wall
Adds minimal additional cost
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Types of Braces
Wood not recommended
Concrete tilt braces or approved equal
Note: Braces must stay in place until roof components are installed.
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Intersection of Other Walls
Wall intersections may substitute for braces
Pilasters may help in spacing braces farther apart
Connection to existing walls
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Adjoining BuildingsRequires scaffold & braces on
same side of wall Creates additional hardship on
contractors Alternative method – use taper
bolts or she bolts connecting new wall to adjacent structural wall Require adjacent building
Owner’s permission
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Adjoining Buildings
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Adjoining Buildings
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Moving braces from one side to another
Sometimes necessary due to work by other trades
Remove braces sequentially from one side of wall to the other
MUST attach additional braces before removing existing
Adding additional coil loops may be necessary: Will help facilitate the moving of braces
while providing a good level of safety for personnel
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Our Nemesis –
WIND:
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Our wind standard: 35 mph
Call the Weather Service Obtain regional wind chart of
historical data Need to know daily wind
speeds Daily wind directions Procure a wind meter
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Establish an Action Level
At winds speeds above 25 mph: Check that braces
are secure Consider evacuation
of scaffold and surrounding areas
Our unbraced, grouted wall deflected less than an inch at 35 mph and fell at a wind speed in excess of 60 mph
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In Conclusion This is NOT intended to be used as a
complete approach to bracing walls ALL relevant factors MUST be
considered Site conditions Weather conditions Wall design Construction sequence Property lines Any other relevant conditions or factors
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References Masonry Bracing Task Force
(Funded by OR-OSHA Grant) Task Force Documentation
Test Report Video