anarchitects_guide to cfmf
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Lesson Agenda
LEED and cold formed steel.
Identify practical uses for cold formed steel (floors,walls, roofs, whole buildings).
Identify the materials that cold formed steel can
efficiently replace (from a cost perspective).
Provide basic design guidelines for what needs toappear on your construction documents.
Provide resources you can use to help your designeffort (the Sweets of cold formed steel).
Answer your questions.
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What Is Cold Formed Steel?
It is typically a recycled
material comes from a millin coils.
The steel is then rolled
into a shape (mostcommonly a C).
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New Designators
600 S 162 - 546 Member
Depth in
1/100 inches
Min. base metalthickness in mils(.054 = 54 mils)
1-5/8
Flange in1/100inches
Stud or Joistwith Stiffener
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LEED with Cold Formed Steel
Steel is the most recycled product in the world.
Cold formed steel is a LEED certified product
based on its virtually 100% recycled steel content.
Adding cold formed steel to your project may add as
many as 2 points towards a LEED certification.
See the Steel Recycling Institutes LEED
documentation letter for further information:
http://www.recycle-steel.org/leed/leed.pdf
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How to LEED with Steel
Go to U.S. Green Building Council
www.usgbc.org
Acquire LEED Green Building Rating System
Go to Steel Recycling Institute:
www.recycle-steel.org
Earn Steel Recycled Content Credit
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Practical Uses For
Cold Formed Steel
PART ONE
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Practical Uses For Cold Formed Steel
Sheathed Floor Systems Concrete Floor Systems
Roof Systems Exterior Wall Systems
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Exterior Wall Systems
Ballston Tower Arlington, Virginia
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Whole Buildings
Substitutes pre-cast concrete & structural steel.
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Notes & Specifications(Give this part to your Structural Engineer)
PART TWO
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Your Drawings Should . . .
Eliminate discrepancies between the architecturaldrawings, structural drawings, and specifications.
Provide sufficient information for the cold formedsteel sub-contractors bidding projects. This will
result in tighter, more competitive bids.
Provide adequate information for the specialty
engineer to design cold formed steel.
Minimize the number of RFIs and change orders
during cold formed steel design and construction.
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Structural Notes (Your Engineers Checklist)
Provide building code and year.
Provide gravity loads (dead and live loads) Provide wind data (wind speed, importance
factor, exposure, and mean roof heights).
Specify deflection criteria for different veneer
materials.
Yes, believe it or not, these items are
frequently missing. However, this is critical
information needed by the specialty engineer.
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Material Specification
Review 5400 specs and make certain that it is
consistent with the architectural design intent on the
drawings and with the structural notes. Indicate galvanizing as G-60 or G-90 (be selective
with G-90 because it is a cost item).
Specify 33 KSI or 50 KSI (50 KSI usually not
necessary in non-bearing wall projects since
deflection usually controls).
Brick Institute recommends a maximum allowable
deflection of L/600 for brick veneer. Please do not
specify a lower deflection criteria.
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Stud Sizing on Drawings
Engineered cold formed steel is a component element usuallyaddressed as a performance specification item. It isengineered and detailed by the specialty engineer who is
typically hired by the contractor.
Specify stud sizes (3 5/8, 6, etc.). The engineer of recordshould help to advise the architect.
Specify maximum stud spacing based on sheathingrequirements or brick tie spacing.
Do not specify gauge of studs unless a minimum gauge is
required for performance. If required state No ExceptionsWill Be Accepted.
If cold formed steel is not addressed in the structural details,
the cold formed steel engineer will follow the architecturalsections. So it is important that the engineer of record reviewthe architectural sections with respect to cold formed steel.
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Exterior
Non-Bearing Walls
PART THREE
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Use slide clips and
deflection tracks to
accommodate for vertical
deflection of the structure.
Specify slide clips wherecurtain wall studs bypass
spandrel beams.
Specify deflection trackswhere curtain wall studs
span between floor levels.
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Hinge BetweenWindow and Studs
Rigid ConnectionDifficult at Slab Edge
Without Steel
Rigid Connection
Difficult at Roof
Without Steel
Provide vertical structural steel below sills of openings wider than12-0. A similar condition may occur at parapet walls.
Provide cold formed steel diagonal braces for headers larger than12-0 or provide structural steel braced frames with infill studs.
Structural Steel 4 to 6 o.c.
and welded to roof structure
Provide Structural Steel BelowOpenings Wider Than 12
Kickers
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Your engineer should verifythat stud depth (4, 6, 8,etc.) will be adequate forspecified deflection limits.
Avoid 12 gauge and 2 1/2flange widths. Providestructural horizontal girtsbetween columns for very
tall exterior studs or allow fordeeper (10 or 12) studs.
Kickers
For greater floor heights
where stud depth is limited,provide diagonal cold formedsteel braces above ceilingsto reduce stud size and
gauge. Provide continuousstructural steel angles underroof decks to support the topof cold formed steel braces.
Steel Angle
Tall Studs &
Limited
Stud Depth
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If cold formed steel is shownon architectural wall
sections and not on
structural drawings, the
structural engineer shouldverify connection points.
(i.e. attaching to bottom of
beam, bearing stud on
metal deck, etc.).
To reduce vertical stud
spans, provide a horizontal
structural beam at the floorlevel of exterior stairwells
and elevator shaft walls.
Provide vertical structuralsteel (skylight curbs) under
skylight mullions imposingthrust loads at top of curb.
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Bearing Walls
PART FOUR
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Rule number one when designing
cold formed steel bearing walls:
LINE UP THE WALLS.
It is critical that cold formed steel bearing wallsalign vertically. If you are not able to vertically
align the bearing walls then you should consider
other framing systems.
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Continuous
Steel Angle
or Tube
Identify stud bearing detail (continuous steel angle at top of
bearing wall).
Hinge
Created
Under
Continuous
Box Header
Wind
Do not provide continuous cold formed steel box headers at
top of bearing walls. This creates a hinge in the wall,
subject to rolling.
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Allow sufficient depthabove doors and
windows toaccommodate the coldformed steel header.
For large openings(i.e., over 10 feet) atwindows and doors,consider structural
steel framing.
Consider thelimitations of cold
formed steel studcolumns. Providestructural steelcolumns instead atsteel beam supports.
Jack Stud
Box Header for
Gravity Loads
(Over Punch
Openings Only)
Full Height
Jamb Studs
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Identify shear wall locations and indicate main framelateral forces to be accommodated in the shear walldesign.
Design the foundations at the shear wall anchorage.Provide enough dead load to resist uplifting force at
each end of the shear wall.Provide Main FrameDesign Wind Loads
Clarify Locations and Lengths of
Shear Walls on Plans
Multiple End
Posts
X-Brace Strap
on Each Side
of Lt. Ga. Wall
Top of Straps
Welded toMultiple End
Posts
Design Foundation To Resist Uplift
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Roof TrussesAnd Rafters
PART FIVE
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Provide dead and live load diagrams for top andbottom chords, for rafters, and for floor/ceiling joists.Provide special loading requirements for situationssuch as attics in buildings or catwalks over retailcanopies.
The structural engineer should verify joist and rafterdepth to support all floor and roof design loads.Truss heel depth should also be verified.
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Additional mechanical loads (RTU) requirementsmust be shown on structural drawings.
Clearly show where special open configurations arerequired for equipment in attic spaces betweentrusses.
Any additional special loads or deflection limits (suchas hanging curtains) must be identified.
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Clearly detail gable end truss or continuation of end
wall studs.
Include design concept to brace walls againsthorizontal thrust from scissors trusses at the top of
bearing walls (i.e. horizontal brace beam at the top ofthe wall under the truss).
Specify Thrust Beam or
Design Wall
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Connections
PART SIX
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Avoid welds or leave connection method openfor specialty engineer.
PAF and screw connections are typicallypreferred by cold formed steel contractors. Beaware that these connectors have lowallowable load capacities.
Beware that screws have very little capacity in
tension in metal decks and cold formed steel.
0.14 diameter is the preferred powder
actuated fastener (PAF) size by most coldformed steel contractors.
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Detail edge conditions so that the minimumedge distance required by fasteners can be
maintained.
3 5/8 Stud
1 Overhang3 To PAF
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The EndThe End