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Masonry Bracing

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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  1. Masonry Bracing Life Safety Considerations During Construction of Masonry Walls

  2. FACTORS TO CONSIDER Who is responsible for wall bracing? • Engineer • General Contractor • Masonry Contractor • Qualified Person

  3. 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

  4. Code Requirements THEN WHAT? • Code does not give direction for spacing of braces • Vertical • Horizontal • Additional Height

  5. 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

  6. Test Wall Construction

  7. 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.

  8. 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

  9. 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

  10. Base Connection Must be evaluated by a Qualified Person • Concrete block deadweight • Test wall deadweight 3400 lbs • Slab connection • Anchor bolt set in concrete

  11. Base Connection Slab Deadmen

  12. Base Connection Wedge Anchor Tang Bolt Super Bolt

  13. Spacing of Braces: Vertical Placement • Code requires Wall Braces above 8 ft. • No direction as to spacing

  14. 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

  15. 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

  16. Types of Braces • Wood not recommended • Concrete tilt braces or approved equal • Note: Braces must stay in place until roofcomponents are installed.

  17. Intersection of Other Walls • Wall intersections may substitute for braces • Pilasters may help in spacing braces farther apart • Connection to existing walls

  18. 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

  19. Adjoining Buildings

  20. Adjoining Buildings

  21. 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

  22. Our Nemesis – WIND:

  23. 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

  24. 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

  25. 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

  26. References • Masonry Bracing Task Force (Funded by OR-OSHA Grant) • Task Force Documentation • TestReport • Video

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