AnArchitects_Guide to Cfmf

7/31/2019 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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