Needham & Associates Consulting Engineers

Needham & AssociatesNeedham & AssociatesConsulting EngineersConsulting Engineers

Fort Wayne, IN - Overland Park, KSFort Wayne, IN - Overland Park, KS

http://www.needhamassoc.comhttp://www.needhamassoc.com

http://www.needhamassoc.com/

Serviceability Design of Serviceability Design of Metal BuildingsMetal Buildings

• Or….Why is my customer so Or….Why is my customer so unhappy???unhappy???

• What does a contractor need to What does a contractor need to know???know???

Your SpeakersYour Speakers• Jeff Needham, PrincipalJeff Needham, Principal

– P.E., S.E in 20 states, started firm in P.E., S.E in 20 states, started firm in 1989 in Fort Wayne1989 in Fort Wayne

– BS and MS from University of KansasBS and MS from University of Kansas

• Andy Carter, PrincipalAndy Carter, Principal– P.E., S.E in 25 states, started in PEMB P.E., S.E in 25 states, started in PEMB

in 1968in 1968

– BS Virginia Military Institute, MS from BS Virginia Military Institute, MS from Georgia TechGeorgia Tech

What Does Needham and What Does Needham and Associates Do?Associates Do?

• General Practice Structural/Civil General Practice Structural/Civil EngineersEngineers

• Consultants to PEMB IndustryConsultants to PEMB Industry– Heavy Structures ( ex: large clear-Heavy Structures ( ex: large clear-spans, steel mills, special structures)spans, steel mills, special structures)

– Hardwall Buildings ( ex: site-cast, tilt-Hardwall Buildings ( ex: site-cast, tilt-up concrete)up concrete)

IntroductionIntroduction

• Why consider Why consider serviceabilityserviceability(source of (source of many problems and claims)many problems and claims)

• Owner input (must have active input, Owner input (must have active input, common problem)common problem)

• Specific to structure’s useSpecific to structure’s use

• Easy to build in, difficult to repairEasy to build in, difficult to repair

Example of Breakdown in Example of Breakdown in Serviceability Serviceability ConsiderationsConsiderations

• Probably lack of communication Probably lack of communication between owner and contractorbetween owner and contractor

• Project in Terra Haute, INProject in Terra Haute, IN

Flammable Vapor Build-up Flammable Vapor Build-up in Insulationin Insulation

Types of Serviceability Types of Serviceability IssuesIssues

• Deflections and Drift (primary focus of this Deflections and Drift (primary focus of this talk)talk)

• Expansion/ContractionExpansion/Contraction

• CamberCamber

• VibrationVibration

• CorrosionCorrosion

• Connection SlipConnection Slip

Responsibility for Responsibility for Determining Serviceability Determining Serviceability RequirementsRequirements• Generally not code issueGenerally not code issue

• Building manufacturer’s consideration Building manufacturer’s consideration only if informed by dealer only if informed by dealer

• Entity (Architect or Owner) specifying the Entity (Architect or Owner) specifying the building parameters specifies criteriabuilding parameters specifies criteria

• Serviceability criteria need owner Serviceability criteria need owner agreement of requirements & costagreement of requirements & cost

Basic Deflection and Drift Basic Deflection and Drift RatiosRatios

Wall Considerations - DriftWall Considerations - Drift

• Metal walls usually have no real limitMetal walls usually have no real limit

• Masonry/tilt-up/precast wall vs. frame driftMasonry/tilt-up/precast wall vs. frame drift

• Base condition free to rotate - H/100Base condition free to rotate - H/100

• Base condition fixed to rotate - H/200Base condition fixed to rotate - H/200

• Do not use unreinforced masonry walls Do not use unreinforced masonry walls with PEMBwith PEMB

Typical NEW PEMB Hardwall Typical NEW PEMB Hardwall BuildingsBuildings

• Designed for strict serviceability issuesDesigned for strict serviceability issues

• Load bearing wallsLoad bearing walls

Wall Considerations - Wall Considerations - DeflectionDeflection

• Wainscot walls & framing aboveWainscot walls & framing above

• Total deflectionTotal deflection– sum of frame drift & girt deflectionsum of frame drift & girt deflection

• Spandrel Beam (single girt) L/240, but Spandrel Beam (single girt) L/240, but not more than 1.5 inchesnot more than 1.5 inches

• Details to enhance compatibility of Details to enhance compatibility of materials, allow for movementsmaterials, allow for movements

Special Considerations for Special Considerations for Bridge CranesBridge Cranes

• Complex topicComplex topic

• Common drift limit H(eave ht)/200 Common drift limit H(eave ht)/200 under crane lateral loadunder crane lateral load

• Crane beam deflection L(bay)/600 for Crane beam deflection L(bay)/600 for vertical deflectionvertical deflection

• Crane beam deflection L(bay)/400 for Crane beam deflection L(bay)/400 for horizontal deflectionhorizontal deflection

Typical Crane InstallationTypical Crane Installation

• Serviceability often controls design as Serviceability often controls design as opposed to strengthopposed to strength

• Steel and weldment fatigue is a major Steel and weldment fatigue is a major serviceability issueserviceability issue

• Therefore, serviceability dictates costTherefore, serviceability dictates cost

Crane Serviceability Crane Serviceability ControlsControls

References for Bridge References for Bridge CranesCranes

• CMAA Standard 74 (Single Girder TR and CMAA Standard 74 (Single Girder TR and UH Cranes) UH Cranes)

• CMAA Standard 70 (Double Girder TR CMAA Standard 70 (Double Girder TR Cranes )Cranes )

• Call (704) 552-8644 to orderCall (704) 552-8644 to order

• About $40 eachAbout $40 each

CMAA Standards 70 and 74CMAA Standards 70 and 74

Interior Partitions & Interior Partitions & Ceiling ConsiderationsCeiling Considerations

• Suspended ceilings will telegraph roof Suspended ceilings will telegraph roof deflectionsdeflections

Sprinkler Heads Indicate Sprinkler Heads Indicate DeflectionDeflection

• Common winter callbackCommon winter callback

• May or may not indicate a real May or may not indicate a real problemproblem



• NoticeableNoticeable– in large open officesin large open offices

– junctions of ceilings & interior wallsjunctions of ceilings & interior walls

Typical Ceiling ProblemTypical Ceiling Problem





• Don’t tie interior partitions to main Don’t tie interior partitions to main framingframing

Good and Bad DetailsGood and Bad Details

Bad GoodBad Good





• Don’t tie interior partitions to main framingDon’t tie interior partitions to main framing

• Remember - Actual deflections are as much Remember - Actual deflections are as much as 25% higher than calculations indicateas 25% higher than calculations indicate

Roof ConsiderationsRoof Considerations

• ““L/Span” deflectionsL/Span” deflections

Comparison of L/Span Comparison of L/Span DeflectionsDeflections

• L/180 on typical Z-purlinL/180 on typical Z-purlin– 20 foot bay = 1.33 inches, 30 foot bay = 2 20 foot bay = 1.33 inches, 30 foot bay = 2

inchesinches

• L/240 on typical roof bar joistL/240 on typical roof bar joist– 30 foot bay = 1.5 inches less initial camber 30 foot bay = 1.5 inches less initial camber

of 3/8of 3/8

– Net deflection is 1.125, much less than Z-Net deflection is 1.125, much less than Z-purlinpurlin

• Z-purlin deflection is magnified by Z-purlin deflection is magnified by “purlin roll”“purlin roll”

Purlin DeflectionPurlin Deflection



• Purlin deflection at eaves and rakesPurlin deflection at eaves and rakes

Eave Deflection/Ice DamEave Deflection/Ice Dam




• Ponding, with low slope roofsPonding, with low slope roofs

PondingPonding

• Common failure type of joist roofs due to Common failure type of joist roofs due to clogged drains, scuppersclogged drains, scuppers

• Can be caused by snow driftingCan be caused by snow drifting

• Design checks for stability failure are usually Design checks for stability failure are usually not required for slopes of 1/4/12 or greaternot required for slopes of 1/4/12 or greater

• Stability checks may be required for slopes of Stability checks may be required for slopes of 1/4/12 or greater if ice dams/snow drifts 1/4/12 or greater if ice dams/snow drifts occur…Be Careful with this condition!occur…Be Careful with this condition!

Ponding Problem on 1/2 to 12 Ponding Problem on 1/2 to 12 SlopeSlope




• Ponding, with low slope roofs Ponding, with low slope roofs

• Panel distress & leakage caused by Panel distress & leakage caused by excessive purlin or frame deflections…excessive purlin or frame deflections…this may be first “clue” of serviceability this may be first “clue” of serviceability issueissue

Non-Deflection/Drift Non-Deflection/Drift ServiceabilityServiceability

• Expansion/ContractionExpansion/Contraction

• Not usually an issue with all steel Not usually an issue with all steel buildingbuilding

• Watch for adjacent structureWatch for adjacent structure

• Watch for collateral materials..tilt-up Watch for collateral materials..tilt-up concrete especiallyconcrete especially

Non-Deflection/Drift Non-Deflection/Drift ServiceabilityServiceability

• CamberCamber

• CorrosionCorrosion

• VibrationVibration

• Connection SlipConnection Slip

SummarySummary

• MBMA states that is up to owner (or his agent) MBMA states that is up to owner (or his agent) to identify all materials so that the metal to identify all materials so that the metal building can be designed to be compatiblebuilding can be designed to be compatible

• Know your owner/customerKnow your owner/customer

• Don’t forget to “program” the job in the rush Don’t forget to “program” the job in the rush to start a design build jobto start a design build job

• Require that manufacturer meet AISC “Steel Require that manufacturer meet AISC “Steel Design Guide 3”Design Guide 3”

AISC “Steel Design Guide AISC “Steel Design Guide 3”3”

• Call AISC 800-644-2400Call AISC 800-644-2400

• Price $16Price $16

Questions????Questions????

Thank You!...Needham & Thank You!...Needham & AssociatesAssociates

Consulting EngineersConsulting Engineers

http://www.needhamassoc.comhttp://www.needhamassoc.com

233 W. Baker St.233 W. Baker St.Fort Wayne, IN 46802Fort Wayne, IN 46802

(219)420-3400(219)420-3400

8417 Santa Fe Dr. 8417 Santa Fe Dr. Overland Park, KS 66212Overland Park, KS 66212

(913)385-5300(913)385-5300

http://www.needhamassoc.com/

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Needham & Associates Consulting Engineers