NAVIGATING AISC 36016 - HSS CONNECTION DESIGN: LIMIT …...design codes, specifications and international guides, including AISC 360 Chapter K (AISC, 2010). An important feature of

NAVIGATING AISC 360-16 HSS CONNECTION

DESIGN: LIMIT STATE TABLES

PRESENTED BY CATHLEEN JACINTO, SE, PEFORSE CONSULTING, LLC

HSS HOLLOW STRUCTURAL SECTIONS

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WELCOME


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WELCOME


q History lessonq Change – the only thing in life that is certain.q Limits of Applicabilityq STI Resource: Limit State Tablesq Limit states in Chapter Jq Additional Resources

AGENDA


HOW WE GOT HERE


HOW WE GOT HERE


HOW WE GOT HERE


HOW WE GOT HERE


q The problem with 360-10, Chapter K is…q Tablesq Prescriptiveq Unique to the Spec

q Content is repetitiveq Limits of Applicability

AISC 360-10, CH K


q “Additional Requirements for HSS and Box-Section Connections”

q Introduction clearly states the requirements of Chapter J also apply

AISC 360-16,CH K


q If met, connections only need to be designed for the provided limit states

q If not met, not prohibited, but must be designed by rational analysis

q Angle (q) – previously was limited to 30° (min) - now user note explains that if < 30°, weld is difficult (still not recommended)

q New limit pertaining to the end of memberq 𝑙"#$ ≥ 𝐷 1.25 − ,-//

0

AISC 360-16,LIMITS OF APPLICABILITY


q Largely unchanged

q New Limit of Applicabilityq Shear tab not mentionedq Cap plate not mentioned

Packer, 2015

ROUND SECTIONS

1

THROUGH PLATE-TO-ROUND HSS CONNECTIONS by Jeffrey A. Packer1

1Bahen/Tanenbaum Professor of Civil Engineering, University of Toronto, Ontario, Canada _____________________________________________________________________________________ Designrecommendationsforlongitudinalandtransversebranch(orgusset)plateT-connections,withtheplatesubjectedtoaquasi-staticloadaxialtotheplate,arenowwell-establishedinmodernsteeldesign codes, specifications and international guides, including AISC 360 Chapter K (AISC, 2010). Animportant feature of all these recommendations, however, is that the connection design capacity isindependentofthesenseofthebranchplateload;i.e.,thesameconnectionstrengthisassumedforbothbranchtensionandcompressionloadingcases,withalowerboundbeingtakentoaccommodatebothloadcases. A widely used stiffening and strengtheningmethod is a plate-to-tube connection where thebranchplate isslottedthroughtheHSSandweldedtotwoopposingfaces(seeFigure1).Thishastheadvantageofengagingmuchmoreofthecrosssectioninloadresistance,andhencehasahighercapacitythantheequivalentbranchplateconnection,but the throughplateconnection isamoredifficultandmoreexpensivefabricationprocedure.Also,apartofthethroughplateprotrudesbeyondthefarsideoftheHSS(Figure1),whichmayaffectconnectionstothatsideoftheHSS.

Figure1:ExampleofathroughplateconnectiontoaroundHSS Researchonlongitudinalthroughplateconnectionstorectangular/squareHSSmembers(KosteskiandPacker,2003)showedthattheconnectionstrengthwasdoublethatoftheequivalentbranchplate


AXIALLY LOADED CONNECTION

MOMENT CONNECTION

HSS 8x8x12 COLUMN

A500CFy = 50 ksiFu = 62 ksi W18x35 BEAM

A992, Fy=50 ksi, Fu=65 ksi,

Pu=60k

AISC 360-10


q AISC 360-16q Per K2.3 – The available strength of connections

to rectangular HSS with concentrated loads shall be determined based on the applicable limit states from Chapter J.

RECTANGULAR SECTIONS


q References Chapter Jq Fundamentally

RECTANGULAR SECTIONS


LIMIT STATE TABLES

STI Resource: Limit State Tablesq How will Tables help?

q Serves as a transition key from AISC 360-10 to AISC 360-16

q Guidance in applying AISC 360-16 Spec Chapter J to HSS Connections

q Provides connection available strength for each HSS limit state

q Clarifies limits of applicability, if anyq Clarifies end distance requirements for each limit

state


LIMIT STATE TABLES

For each limit state:

q AISC 360-10 and 14th Ed. Manual in left column

q AISC 360-16 and 15th Ed. Manual in right column


LIMIT STATE TABLES

For each limit state:q Connection

capacity equation references

q Variable substitutions specific to HSS

q Limits of applicability in AISC 360-16 only where specifically noted


LIMIT STATE TABLES

SHEARAXIAL

TRUSSMOMENT


LIMIT STATE TABLES

q Summary of Tablesq SHEAR

q Load parallel to HSS longitudinal axisq WF Beam to Round, Rect, and Square HSS Columnq Single plate, Through plate, L, 2L, WT, Seated Conns

q AXIALq Load perpendicular to HSS longitudinal axisq Plate to Round and Rectangular/Square HSS Conns

q TRUSSq Branch HSS-to-Chord HSS Truss Connections in T/C

q MOMENTq Branches under IP or OOP Bending Moment to HSS

Chordsq Table Notes and Definition of Parameters


SUMMARY OF LIMIT STATES


RESOURCE - LIMIT STATE TABLE - SHEAR

STEELTUBEINSTITUTE 4/6/18

AISCSpecificationandManualReferences

AISC360-10and14thEd.Manualpp.

10-102to10-107


10-87to10-91

AISC360-10and14thEd.Manualpp.10-102

to10-107


to10-91


to10-134


to10-119


to10-12


to10-12


10-138to10-139


10-123to10-124


to10-88


to10-73


to10-96

AISC360-16and15thEd.Manualpp.10-78to10-81and10-153

AISCManualConsiderationsSpecifictoHSSElements

14thEd.Manualpp.10-167








SimilartoDoubleAngleConsiderationsperManualpp.10-167






Wallslenderness Manualpp.10-167 Manualpp.10-153 Manualpp.10-168 Manualpp.10-154 _ _ _ _ _ _ _ _Manualpp.10-168forverticalstiffenerplate

Manualpp.10-153forverticalstiffenerplate

HSSShearRuptureatWeld

HSSShearYieldingatWeld _ _ _ _ _ _ _ _ _ _ _ _

HSSPunchingShear

SpecEq.(K1-3)

subjecttolimitsinTableK1.1AorTableK1.2A

ManualEq.(10-7) _ _ _ _ _ _ _ _ _ _

SpecEq.(K1-3)


ManualEq.(10-7)atverticalstiffenerplate

Yieldlineplasticity _ _ _ _ _ _ _ _ _ _ _ _ Manualpp.10-168andTable10-15

Manualpp.10-153andTable10-15

AdditionalHSSProvisions _ _ _ _

GuidelinesforweldatHSScolumnworkableflatdimensionsperManual

pp.10-169


pp.10-155

GuidelinesforweldtoHSScolumnworkableflatdimensionsperManual

pp.10-167


pp.10-152



_ _

ManualEq.(9-2),andDG24Eq.(2-4)


DG24Eq.(2-3)

ManualTable10-15

HSSColumn






UnstiffenedSeat StiffenedSeat

LIMITSTATETABLEPERAISCSPECIFICATION360-16ANDTHE15THEDITIONSTEELCONSTRUCTIONMANUAL

Element

LimitState

SHEARLOADPARALLELTOHSSLONGITUDINALAXIS

WFBeamConnectionstoRound,Rectangular,andSquareHSS

SinglePlate(ConventionalandExtendedConfigurations)

ThroughPlate SingleAngle DoubleAngle WT

STEELTUBEINSTITUTE 4/6/18

AISCSpecificationandManualReferences


10-102to10-107


10-87to10-91


to10-107


to10-91


to10-134


to10-119


to10-12


to10-12


10-138to10-139


10-123to10-124


to10-88


to10-73


to10-96

AISC360-16and15thEd.Manualpp.10-78to10-81and10-153

AISCManualConsiderationsSpecifictoHSSElements















Wallslenderness Manualpp.10-167 Manualpp.10-153 Manualpp.10-168 Manualpp.10-154 _ _ _ _ _ _ _ _Manualpp.10-168forverticalstiffenerplate

Manualpp.10-153forverticalstiffenerplate

HSSShearRuptureatWeld

HSSShearYieldingatWeld _ _ _ _ _ _ _ _ _ _ _ _

HSSPunchingShear

SpecEq.(K1-3)


ManualEq.(10-7) _ _ _ _ _ _ _ _ _ _

SpecEq.(K1-3)


ManualEq.(10-7)atverticalstiffenerplate

Yieldlineplasticity _ _ _ _ _ _ _ _ _ _ _ _ Manualpp.10-168andTable10-15

Manualpp.10-153andTable10-15

AdditionalHSSProvisions _ _ _ _


pp.10-169


pp.10-155


pp.10-167


pp.10-152



_ _



DG24Eq.(2-3)

ManualTable10-15

HSSColumn






UnstiffenedSeat StiffenedSeat

LIMITSTATETABLEPERAISCSPECIFICATION360-16ANDTHE15THEDITIONSTEELCONSTRUCTIONMANUAL

Element

LimitState

SHEARLOADPARALLELTOHSSLONGITUDINALAXIS

WFBeamConnectionstoRound,Rectangular,andSquareHSS

SinglePlate(ConventionalandExtendedConfigurations)

ThroughPlate SingleAngle DoubleAngle WT


RESOURCE – LIMIT STATE TABLE - AXIAL


RESOURCE – LIMIT STATE TABLE - TRUSS


LIMIT STATE TABLE -MOMENT


§ Although end distance is mentioned in a few tables in Chapter K, it should be considered for each individual limit state.

§ STI resource is available to guide for rectangular sections:§ https://steeltubeinstitute.org/hss/2017/05/31/rectangul

ar-hss-connections-close-chord-end/

A WORD ON END DISTANCES

https://steeltubeinstitute.org/hss/2017/05/31/rectangular-hss-connections-close-chord-end/


LIMIT STATE TABLE: END DISTANCES


q General Provisions & Parameters for HSS Connections

q Effective Width Formula, Be

AISC 360-16, SECTION K1

= Bep= beoi

From 360-10


LIMIT STATE TABLE: EFFECTIVE WIDTH


5

solutionforsuchacombinedfailuremechanismbut itwastoocomplex forroutinedesignanddesign

recommendations have opted instead for discrete individual limit state checks. Importantly though,

DaviesandPacker(1982)showedthattheformulationtocaptureLocalyieldingofthebranchplate,Eqn.(K1-7),representedalowerboundtoboththeircombinedplastification-and-punchingmechanismaswell

asexperimentalresults,furthersubstantiatingthediscussionaboveregardingthesethreefailuremodes.

Figure4:Atension-loaded,transversebranchplateconnectionexhibitingthreefailuremechanisms:(i)

PlastificationoftheHSSface;(ii)PunchingshearoftheHSSconnectingface;(iii)LocalyieldingofHSSsidewalls

4.LocalyieldingofHSSsidewalls. Thislimitstate,showninFigure4,canoccurwiththebranchplateloadedineithertensionor

compressionwhenβiscloseto1.0.ItismanifestedbyyieldingofthetwoHSSsidewalls,orwebs,along

ashortdispersed load lengthdirectlybeneaththebranchplate. If the load isdispersedfroman initial

bearing length to the bottomof theHSS corner radius (analogous to dispersion to the k-line in aW-

section),atadispersionslopeof2.5:1,thenthetotalavailableyieldstrengthforthetwowebsis

Rn=2Fyt(5k+tp), wherek=outsidecornerradius (K1-9)and(J10-2)

5.LocalcripplingofHSSsidewalls. This limitstate,pertainingtobranchcompression loadonly,coversbucklingfailureofthetwo

sidewallswhenβiscloseto1.0.Forasingleconcentratedforce,correspondingtoaplate-to-HSST-

LIMIT STATE: HSS PUNCHING

Packer, 2015




Section J10.10 Transverse Forces on Plate Elements

Page 9-14 “Plate Elements Subjected to Out-of-Plane Loads”

R2 = 0.60F7t9 2c;<< + 2L (15th Ed. Manual, Eq. 9-29)



LIMIT STATE TABLE:PUNCHING


LIMIT STATE: HSS PLASTIFICATION

Packer, 2015




Section J10.10 Transverse Forces on Plate Elements refers to Section J4.5

Flexural yield-line mechanism must be derived.

Page 9-16 “For out-of-plane transverse loads”




360-10, K2. HSS-to-HSS Truss Connections

360-16, Equation (9-30)

𝑎 ≠ 𝑏15

thEd

Man

ual,

Fig.

9-5

(a)


LIMIT STATE TABLE:HSS PLASTIFICATION


5

solutionforsuchacombinedfailuremechanismbut itwastoocomplex forroutinedesignanddesign

recommendations have opted instead for discrete individual limit state checks. Importantly though,

DaviesandPacker(1982)showedthattheformulationtocaptureLocalyieldingofthebranchplate,Eqn.(K1-7),representedalowerboundtoboththeircombinedplastification-and-punchingmechanismaswell

asexperimentalresults,furthersubstantiatingthediscussionaboveregardingthesethreefailuremodes.

Figure4:Atension-loaded,transversebranchplateconnectionexhibitingthreefailuremechanisms:(i)

PlastificationoftheHSSface;(ii)PunchingshearoftheHSSconnectingface;(iii)LocalyieldingofHSSsidewalls

4.LocalyieldingofHSSsidewalls. Thislimitstate,showninFigure4,canoccurwiththebranchplateloadedineithertensionor

compressionwhenβiscloseto1.0.ItismanifestedbyyieldingofthetwoHSSsidewalls,orwebs,along

ashortdispersed load lengthdirectlybeneaththebranchplate. If the load isdispersedfroman initial

bearing length to the bottomof theHSS corner radius (analogous to dispersion to the k-line in aW-

section),atadispersionslopeof2.5:1,thenthetotalavailableyieldstrengthforthetwowebsis

Rn=2Fyt(5k+tp), wherek=outsidecornerradius (K1-9)and(J10-2)

5.LocalcripplingofHSSsidewalls. This limitstate,pertainingtobranchcompression loadonly,coversbucklingfailureofthetwo

sidewallswhenβiscloseto1.0.Forasingleconcentratedforce,correspondingtoaplate-to-HSST-

LIMIT STATE: LOCAL YIELDING OF HSS SIDEWALLS

Packer, 2015


AISC 360-16 Section J10.2 – Web Local Yielding

R2 = F7BtB 5k + lE (J10-2)tw = 2* tdes (design thickness of 2 HSS walls)

LIMIT STATE: LOCAL YIELDING OF HSS SIDEWALLS


LIMIT STATE TABLE:HSS SIDEWALL YIELDING


6

connection, the available strength differs from internationalHSS connection recommendations and isadaptedbyAISCfromtheweblocalcripplingexpressionforaW-sectionweb: Rn=1.6t2[1+3tp/(H–3t)][EFy]0.5Qf (K1-10)and(J10-4)Similarly,forapairofconcentratedforces,correspondingtoaplate-to-HSSCross-(orX-)connection(seeFigure 5), the available strength differs from international HSS connection recommendations and isadaptedbyAISCfromtheweblocalbucklingexpressionforaW-sectionweb: Rn=[48t3/(H–3t)][EFy]0.5Qf (K1-11)and(J10-8)

Figure5:BucklingofHSSsidewallsundertransversecompression

LimitsofApplicability TableK1.2AofAISC360-10givesarangeofvalidityforanumberofgeometricandmechanicalpropertiesforwhichallofTableK1.2wouldbevalid.AlllimitswouldnotapplytoallthelimitstatesinTableK1.2.Fortransverseplateconnections,Eqns.(K1-7)and(K1-8),correspondingtoLimitStates2and3 above, contain effective width terms which have been derived from research – predominantlyexperimental–inwhichthewallslendernesslimits(B/tandH/t≤35)andwidthratio(1.0≥Bp/B≥0.25)representedtheboundsofthetestdataatthetime.Similarly,themechanicalpropertylimitationsalsorepresentedthelimitsoftestevidenceforLimitStates2and3,atthetime.Asnotedpreviously,LimitState1isagenericanalyticalsolution.LimitState4isverysimilartointernationalrecommendationsandisfundamentaltomoststeeldesignstandards.LimitState5availablestrengthexpressions(andtheir

LIMIT STATE: LOCAL CRIPPLING/BUCKLING OF HSS SIDEWALLS


AISC 360-16 Section J10.3 (Web Local Crippling)

AISC 360-16 Section J10.5 (Web Compression Buckling)

LIMIT STATE: LOCAL CRIPPLING/BUCKLING OF HSS SIDEWALLS


qt9 ≤GHGIJ

t (Eqn K1-3) based on relative strength of the HSS and the shear tab.

qSpecification Committee voted to base the check on the assumed demand moment due to beam reaction and move it out of the spec and into Part 10 of the Manual.

SHEAR TAB CONNECTION


qAs long as HSS walls are classified as not slender, the distortion of the wall is insignificant to the column strength.

qPlastification doesn’t control.qOnly check punching shear (shear rupture).

qRKe ≤MGHNOJP

Q (Manual Eq.10-7a)

SHEAR TAB CONNECTION


LIMIT STATE TABLE:SHEAR TAB


CAP PLATE CONNECTION

Cap Plate – For Round and Rectangular HSS360-16 Section J10.2 – Web Local YieldingR2 = F7BtB 5k + lE (J10-2)

tw = 2* tdes

k = tp (cap plate thickness)lb = b (t of connecting plate)

AISC 360-10

R2 = 2F7tR;S 5𝑡U + b AISC 360-10


Cap Plate – For Round and Rectangular HSSIf 5𝑡U + b ≥ B → 𝑅# = 𝐹[A

All 4 sides are engagedCap plate needs to be of sufficient thickness

CAP PLATE CONNECTION


LIMIT STATE TABLE:CAP PLATE CONNECTION


A NOTE ABOUT Qf

q Main member stress functionq Reduces the local strength at the connectionq For rounds 0.4 ≤ Q< ≤ 1.0

q Q< = 1 for HSS in tensionq Q<= 1.0 – 0.3U(1+U) for HSS in compression (K2-3)

q where U = `abGcde

+ fabGcg

(K2-4)q (side with lower compression)


A NOTE ABOUT Qf

q For rectangles 0.5 ≤ Q< ≤ 1.0q Q< = 1 for HSS in tensionq 𝑄i = 1.3 − 0.4 k

l≤ 1.0 for T-, Y-, X- conn (K3-14)

q 𝑄i = 1.3 − 0.4 klmnn

≤ 1.0 for gapped K- conn (K3-15)

q where U = `abGcde

+ fabGcg

(K2-4)

q (side with higher compression)


RESOURCE – LIMIT STATE TABLE

q https://steeltubeinstitute.org/hss/hss-information/aisc-360-16/

https://steeltubeinstitute.org/hss/hss-information/aisc-360-16/


§ Next month’s webinar expands on this through worked design examples.

§ STI’s Design Manuals Volumes 3 & 4 – available by April, 2020

§ AISC’s Design Guide 24 is currently being updated (expected late 2020)

§ Steelwise by Carlo Lini, Modern Steel Construction, June 2019

ADDITIONAL RESOURCES


§ STI’s Limit State Tables are…a) Free to AISC membersb) Free to AARP membersc) Free if you know the secret handshaked) Free to everyone

POLLING QUESTION 1


§Do you want a PDH certificate for this webinar? a) Yesb) No

POLLING QUESTION 2

NAVIGATING AISC 360-16 HSS CONNECTION

DESIGN: LIMIT STATE TABLES

PRESENTED BY CATHLEEN JACINTO, SE, PEFORSE CONSULTING, LLC

[email protected]

NAVIGATING AISC 36016 - HSS CONNECTION DESIGN: LIMIT …...design codes, specifications and international guides, including AISC 360 Chapter K (AISC, 2010). An important feature of

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