LATERAL DRIFT DESIGN IN COLD FORMED STEEL WALL …...upon limiting distress to finishes based on...

Feb. 22, 2012 CFSEI

LATERAL DRIFT DESIGN IN COLD FORMED STEEL WALL

SYSTEMS

Thomas Castle, S.E.

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Feb. 22, 2012 CFSEI

This presentation is published by the Cold-Formed Steel Engineers Institute (“CFSEI”). The information herein shall not constitute any representation or warranty, express or implied, on the part of CFSEI or any individual that the information is suitable for any general or specific purpose, and should not be used without consulting with a qualified engineer, architect, or building designer. Any individual or entity making use of the information provided herein assumes all risks and liabilities arising or resulting from such use. CFSEI believes that the information presented is in conformance with prevailing engineering standards of practice. However, none of the information provided is intended to represent any official position of the CFSEI or to exclude the use and implementation of any other design or construction technique. Opinions expressed are those of the presenter alone, and do not reflect an official position of the CFSEI, the Steel Framing Alliance, or the American Iron and Steel Institute. This presentation is not intended to be a substitute for appropriate legal advice from a qualified legal professional.

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Feb. 22, 2012 CFSEI

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

The Steel Framing Alliance is a Registered Provider with the American Institute of Architects Continuing Education Program. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.

SFA l.5 LU/HSW

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Feb. 22, 2012 CFSEI

Introduction • Overview of Non Structural Wall Systems • Code Requirements for Drift Accommodation • Typical Configurations • Details and Detailing • Challenging Conditions • Interior Framing • Summary

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Feb. 22, 2012 CFSEI

Overview of Non Structural Wall Systems

• Structural Design • Wind Design Loads • Seismic Deign Loads • Deflection Limitations

• Accommodate Building Movement • Typical Vertical Movements • Typical Lateral Drifts

• Refer to CSFEI Tech Note 542

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Feb. 22, 2012 CFSEI

Wind Design Loads

• Loads decrease with increased Tributary Area

• Suction Loads typically govern and are typically constant over height of building.

GCp = 1.4 (Elements in areas of discontinuity)

GCp = 1.1 (Elements not in areas of discontinuity)

P = qh(GCp-GCpi)

• 2006 International Building Code (ASCE-7 6.5.12.4) Wind Loads Component and Cladding

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Feb. 22, 2012 CFSEI

Seismic Design Loads

• Loads Increase with Building Height

• 2009 International Building Code Seismic Loads – ASCE 7 -13.3 - Nonstructural Components

Fp = 0.4apSDSIp

Rp ( ) 1 + 2 h

z

ap = 1.0 and Rp =2.5 (Table 13.5-1 – Either Interior or Exterior Walls)

For Fasteners of the Connecting system ap = 1.25 and Rp = 1.0 (Exterior Only)

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Feb. 22, 2012 CFSEI

Deflection Limitations • Out-of-plane deflection limitations are based

upon limiting distress to finishes based on curvature of wall system.

– Metal Panels: L/180 to L/240 – EIFS: L/240 to L/360 – Cement Plaster: L/360 – Brick Veneer: L/360 to L/600 or more – Stone Veneer: L/480 to L/600

• Out-of-plane deflections for cold formed wall systems are most always governed by wind loading.

• 1604.3 – Serviceability limits for wall deflections based upon 70% of Component and Cladding Loads

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Feb. 22, 2012 CFSEI

Accommodation of Building Movements

• Accommodation of Building Movements

– Isolate the Wall System from the Structure – Vertical Deflection of Perimeter Beams/Slabs – Lateral Drift of Building Frame System

• Isolate Relatively Light Building Exterior from

Inadvertent Loads caused by Expected Building Deformation.

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Feb. 22, 2012 CFSEI


Vertical Deflection of Perimeter Beams/Slabs • With typical 30 foot spans and design live load

deflections of L/360, building live load deflections can reach 1 inch.

• Value for perimeter beam live load deflection is typically limited to ¾ inch or less.

• Actual design value must be verified with Engineer of Record for structure.

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Feb. 22, 2012 CFSEI


Lateral Drift of Typical Systems • Actual drift should be obtained from Engineer of

Record for structure • For Category II structure Da can be 2.5% of story

height. • For 15 foot floor height and 2.5% drift Da = 4 ½

inches

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Feb. 22, 2012 CFSEI

Building Systems vs. Finish System

• Steel Moment Frames • Concrete Moment Frames • Eccentric Braced Frames • Concentric Braced Frames • Concrete Shear Walls

• EIFS Systems • Cement Plaster Systems • Adhered Veneer Systems • Anchored Veneer and

Stone Systems

RIGID SYSTEMS

FLEXIBLE SYSTEMS BUILDING SYSTEMS FINISH SYSTEMS

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Feb. 22, 2012 CFSEI

Code Requirements for Drift Accommodation

• ASCE 7 – 13.5.2

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• ASCE 7 – 13.5.3

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• ASCE 7 – 13.5.3

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• 2010 California Building Code Title 24 Requirement for DSA and OSHPD

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Feb. 22, 2012 CFSEI


• ASCE 7 – 13.5.9

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Feb. 22, 2012 CFSEI


ASCE 13.5.9 Dfallout >= 1.25 I Dp

Exceptions:

Glass with Sufficient Clearance to its frame such that physical contact between the glass and frame will not occur at 1.25 Dp

Fully tempered monolithic glass no more than 10 feet above a walking surface

Annealed or heat treated laminated glass that is captured mechanically by a wall system glazing pocket

Dfallout is determined in accordance with AAMA 501.6 or by engineering analysis

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Feb. 22, 2012 CFSEI

FEMA P-749 – Seismic

Performance • Limit the chance of total or partial collapse as a result of

MCER ground motions to various percentages depending upon Occupancy Categories

• For all structures, minimize the risk that, in likely earthquakes, debris generated by damage to cladding, ceilings, or mechanical or electrical systems will fall on building occupants or pedestrians.

• To the extent practicable, avoid economic losses associated with damage to structural and nonstructural systems as a result of relatively frequent moderate earthquake events.

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Feb. 22, 2012 CFSEI

Accommodation of Lateral Deflection

Building Deformed Shape

Building Original Shape

Wall Moves with Floor Below and Slips Past Floor Above

Da Interstory

D Total

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Feb. 22, 2012 CFSEI

Typical Wall Configurations

• Balloon Framed Systems • Floor to Floor Framed Systems

• Spandrel Framed Systems • Panelized Systems

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Balloon Framed Systems 22

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Balloon Framed Systems

Vertical Slip Connection

Bearing Connection

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Feb. 22, 2012 CFSEI

Vertical Slip Connections

(Also Refer to CFSEI Tech Note W103-11)

Balloon Framed Systems 24

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Floor to Floor Framed Systems

FICCADENTI WAGGONER & CASTLE CONSULTING STRUCTURAL ENGINEERS

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Bearing Connection Each Floor

Concrete Slab

Expansion Joint for Vertical and Lateral Movement

Floor to Floor Framed Systems

Expansion Joint for Vertical and Lateral Movement

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Feb. 22, 2012 CFSEI

Floor to Floor Framing w/ Joint Below Floor Line

Da Interstory

D Total

Joint at Underside of Floor

Floor to Floor Framed Systems 27

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Da Interstory

D Total

Joint at Underside of Floor


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Da Interstory

D Total


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Spandrel Framed Systems

Framing

Framing

Framing

Windows

Windows

Windows

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Isolation Joint Allowing Vertical / Lateral Movement

Spandrel Framed Systems 31

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Rigid Connection


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Kicker Connection


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Spandrel Framing w/ Joint at Head of Window

Da Interstory

D Total

Joint at Head of Window

Floor Beyond


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Da Interstory

D Total

Joint at Head of Window


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Da Interstory

D Total


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Details

• Track within a Track – Refer to CFSEI Tech Note W101-09)

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Details

• Track within a Track

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Details

• Slip Track Refer to CFSEI Tech Note W100-08a

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Details

• Slip Track

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Details

• Sliding Clips Refer to CFSEI Tech Note W103-11

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Details

• Rigid Clips – Design to take Seismic In Plane loading if Required and Remain Ductile if Required

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Feb. 22, 2012 CFSEI

Details

• Rigid Clips

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Details

• Rigid Clips

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Feb. 22, 2012 CFSEI

Details

• Rigid Clips – Design to have Ductile Bending and

Avoid Fastener Failure

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Feb. 22, 2012 CFSEI

Challenges with Accommodating Lateral Drift

At Building Corners:

Spandrel Framing Floor to Floor Framing

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Feb. 22, 2012 CFSEI


At Building Corners:

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Feb. 22, 2012 CFSEI

FEMA P-749 – Seismic

Performance • Limit the chance of total or partial collapse as a result of

MCER ground motions to various percentages depending upon Occupancy Categories

• For all structures, minimize the risk that, in likely earthquakes, debris generated by damage to cladding, ceilings, or mechanical or electrical systems will fall on building occupants or pedestrians.

• To the extent practicable, avoid economic losses associated with damage to structural and nonstructural systems as a result of relatively frequent moderate earthquake events.

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Feb. 22, 2012 CFSEI

Avoid Beams in Wall Space or Vertically Offset Joints:


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Feb. 22, 2012 CFSEI

Avoid Columns in Wall Space:

Da Interstory


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Integration with Glass Wall Systems:


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Feb. 22, 2012 CFSEI

Utilities in Walls can Cross Joints and Must be Designed to Prevent Locking Joint


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Feb. 22, 2012 CFSEI

Interior Framing Why not treat them the same as Exterior Framing?

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Feb. 22, 2012 CFSEI


•Finishes are not usually as heavy

•Falling hazards are not usually as great

•Typically interior contains numerous corners and intersections

•MEP penetrations are more extensive

•Beams and columns are contained in walls

•Ceilings are typically braced to floor above

•Life Safety systems can become compromised if walls shift differently than floor above.

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Feb. 22, 2012 CFSEI


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Feb. 22, 2012 CFSEI

Interior Framing Why not treat them the same as Exterior Framing? Make attachments top and bottom ductile. Control failure method to avoid undesirable outcomes (falling hazards).

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Feb. 22, 2012 CFSEI

Bearing Walls ? 57

Feb. 22, 2012 CFSEI

Bearing Walls ?

• A wall that is part of the structural system moves with the building and is designed to do so.

• A non structural element could be designed to do the same.

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Feb. 22, 2012 CFSEI

Real World 59

LATERAL DRIFT DESIGN IN COLD FORMED STEEL WALL …...upon limiting distress to finishes based on...

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