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Masonry Bracing. Life Safety Considerations During Construction of Masonry Walls. FACTORS TO CONSIDER. Who is responsible for wall bracing? Engineer General Contractor Masonry Contractor Qualified Person. CODE REQUIREMENTS.

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Masonry Bracing

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Masonry Bracing

Life Safety Considerations During Construction of Masonry Walls


FACTORS TO CONSIDER

Who is responsible for wall bracing?

  • Engineer

  • General Contractor

  • Masonry Contractor

  • Qualified Person


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


Code Requirements

THEN WHAT?

  • Code does not give direction for spacing of braces

    • Vertical

    • Horizontal

    • Additional Height


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


Test Wall Construction


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.


Test Wall Construction

Wall Brace connection

  • Coil Loop Inserts installed around a vertical rebar and placed behind a horizontal rebar as shown

Picture of coil here


Test Wall Construction

Why 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


Base Connection

Must be evaluated by a Qualified Person

  • Concrete block deadweight

    • Test wall deadweight 3400 lbs

  • Slab connection

  • Anchor bolt set in concrete


Base Connection

Slab

Deadmen


Base Connection

Wedge Anchor

Tang Bolt

Super Bolt


Spacing of Braces:

Vertical Placement

  • Code requires Wall Braces above 8 ft.

  • No direction as to spacing


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


Spacing of Braces:

What does all of this do?

  • Creates a crisscross rebar mat in the wall

  • Uses materials already in wall

  • Adds minimaladditional cost


Types of Braces

  • Wood not recommended

  • Concrete tilt braces or approved equal

  • Note: Braces must stay in place until roofcomponents are installed.


Intersection of Other Walls

  • Wall intersections may substitute for braces

  • Pilasters may help in spacing braces farther apart

  • Connection to existing walls


Adjoining Buildings

Requires 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


Adjoining Buildings


Adjoining Buildings


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


Our Nemesis –

WIND:


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


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


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


References

  • Masonry Bracing Task Force (Funded by OR-OSHA Grant)

    • Task Force Documentation

      • TestReport

      • Video


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